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New submissions for Wed, 20 May 20

[1]  arXiv:2005.08940 [pdf]

Title: A Starshot Communication Downlink

Authors: Kevin L. G. Parkin

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Breakthrough Starshot is an initiative to propel a sailcraft to Alpha Centauri within the next generation. As the sailcraft transits Alpha Centauri at 0.2 c, it looks for signs of life by imaging planets and gathering other scientific data. After the transit, the 4.1-meter diameter sailcraft downlinks its data to an Earth-based receiver. The present work estimates the raw data rate of a 1.02 {\mu}m, 100 Watt laser that is received at 1.25 {\mu}m by a 30-meter telescope. The telescope receives 288 signal photons per second (-133 dBm) from the sailcraft after accounting for optical gains (+296 dBi), conventional losses (-476 dB), relativistic effects (-3.5 dB), and link margin (-3.0 dB). For this photon-starved Poisson channel with 0.1 nm equivalent noise bandwidth, 90% detector quantum efficiency, 1024-ary PPM modulation, and 10^-3 raw bit error rate, the raw data rate is 260 bit/s (hard-decision) to 1.5 kbit/s (ideal) raw data rate, which is 8-50 Gbit/year. This rate is slowed by noise, especially starlight from Alpha Centauri A scattered into the detector by the atmosphere and receiver optics as sailcraft nears the star. Because this is a flyby mission (the sailcraft does not stop in the Centauri system), the proper motion of Alpha Centauri relative to Earth carries it away from the sailcraft after transit, and the noise subsides over days to weeks. The downlink can resume as soon as a day after transit, starting at 7-22 bit/s and reaching nearly full speed after 4 months. By using a coronagraph on the receiving telescope, full-rate downlink speed could be reached much sooner.

[2]  arXiv:2005.08971 [pdf, other]

Title: Simba: The average properties of the circumgalactic medium of $2 \leq z \leq 3$ quasars are determined primarily by stellar feedback

Authors: Daniele Sorini, Romeel Davé, Daniel Anglés-Alcázar

Comments: Main text: 19 pages; appendix: 4 pages; 12 figures; submitted to MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We use the Simba cosmological hydrodynamic simulation suite to explore the impact of feedback on the circumgalactic medium (CGM) and intergalactic medium (IGM) around $2 \leq z \leq 3$ quasars. We identify quasars in Simba as the most rapidly-accreting black holes, and show that they are well-matched in bolometric luminosity and correlation strength to real quasars. We extract Lyman-alpha (Ly-a) absorption in spectra passing at different transverse distances (10 kpc $\lesssim b \lesssim$ 10 Mpc) around those quasars, and compare to observations of the mean Ly-a absorption profile. The observations are well reproduced, except within 100 kpc from the foreground quasar, where Simba overproduces absorption; this could potentially be mitigated by including ionisation from the quasar itself. By comparing runs with different feedback modules activated, we find that (mechanical) AGN feedback has little impact on the surrounding CGM even around these most highly luminous black holes, while stellar feedback has a significant impact. By further investigating thermodynamic and kinematic properties of CGM gas, we find that stellar feedback, and not AGN feedback, is the primary physical driver in determining the average properties of the CGM around $z\sim 2-3$ quasars. We also compare our results with previous works, and find that Simba predicts much more absorption within 100 kpc than the Nyx and Illustris simulations, showing that the Ly-a absorption profile can be a powerful constraint on simulations. Instruments such as VLT-MUSE and upcoming surveys (e.g., WEAVE and DESI) promise to further improve such constraints.

[3]  arXiv:2005.08974 [pdf, ps, other]

Title: Simulations of Tidal Disruption Events

Authors: Giuseppe Lodato (1), Roseanne M. Cheng (2), Clement Bonnerot (3), Linxin Dai (4) ((1) Dipartimento di Fisica, Universita' degli Studi di Milano, Italy, (2) Theoretical Division, Los Alamos National Laboratory, (3) TAPIR, California Institute of Technology, (4) Department of Physics, The University of Hong Kong)

Comments: 34 pages, Accepted chapter for Springer Space Science Reviews book on Tidal Disruption Events

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Numerical simulations have historically played a major role in understanding the hydrodynamics of the tidal disruption process. Given the complexity of the geometry of the system, the challenges posed by the problem have indeed stimulated much work on the numerical side. Smoothed Particles Hydrodynamics methods, for example, have seen their very first applications in the context of tidal disruption and still play a major role to this day. Likewise, initial attempts at simulating the evolution of the disrupted star with the so-called affine method have been historically very useful. In this Chapter, we provide an overview of the numerical techniques used in the field and of their limitations, and summarize the work that has been done to simulate numerically the tidal disruption process.

[4]  arXiv:2005.08975 [pdf, other]

Title: Self-gravitating dark matter gets in shape

Authors: Jenny Wagner

Comments: 5 pages, honorable mention at the 2020 Gravity Research Foundation essay competition, submitted to IJMPD

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

In our current best cosmological model, the vast majority of matter in the Universe is dark, consisting of yet undetected, non-baryonic particles that do not interact electro-magnetically. So far, the only significant evidence for dark matter has been found in its gravitational interaction, as observed in galaxy rotation curves or gravitational lensing effects. The inferred dark matter agglomerations follow almost universal mass density profiles that can be reproduced well in simulations, but have eluded an explanation from a theoretical viewpoint. Forgoing standard (astro-)physical methods, I show that it is possible to derive these profiles from an intriguingly simple mathematical approach that directly determines the most likely spatial configuration of a self-gravitating ensemble of collisionless dark matter particles.

[5]  arXiv:2005.08977 [pdf, other]

Title: Antisymmetric cross-correlation of line-intensity maps as a probe of reionization

Authors: Gabriela Sato-Polito, José Luis Bernal, Ely D. Kovetz, Marc Kamionkowski

Comments: 9 pages, 3 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present a new estimator for the cross-correlation signal between line intensity maps to probe the Epoch of Reionization. The proposed estimator is the hitherto neglected antisymmetric component of the cross-correlation, under the exchange of line-of-sight positions. We consider the cross-correlation between HI and CO fluctuations, and forecast the improvement in precision on reionization parameters when the antisymmetric contribution is accounted for. As a way to break the degeneracy between astrophysics and cosmology in the intensity mapping power spectrum, we study the ratio between the antisymmetric and symmetric components. While our results depend on the highly uncertain astrophysical modelling, we show that in most standard scenarios including the antisymmetric contribution as a complementary probe can lead to a significant gain in information.

[6]  arXiv:2005.08982 [pdf, other]

Title: Millisecond Pulsars Modify the Radio-SFR Correlation in Quiescent Galaxies

Authors: Takahiro Sudoh, Tim Linden, John F. Beacom

Comments: Main text 11 pages, 2 figures. Comments welcome

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

The observed correlation between the far-infrared (FIR) and radio luminosities of star-forming galaxies shows the close connection between star formation and cosmic-ray production. LOFAR recently extended radio observations of the related correlation with star formation rate to lower frequencies (150~MHz), finding a peculiar radio excess in galaxies with high stellar masses and low star-formation rates. We show that recycled/millisecond pulsars (MSPs) can dominate the non-thermal emission in these massive quiescent galaxies and explain the excess. This is supported by recent data suggesting that MSPs can efficiently convert a large fraction of their spin-down power to e$^+$e$^-$ pairs. We find that MSP-based models provide a significantly improved (formally $>19\sigma$, though systematic errors dominate) fit to LOFAR data. We discuss implications for the radio-FIR correlation, the observation of radio excesses in nearby galaxies, and local electron and positron observations.

[7]  arXiv:2005.08983 [pdf, other]

Title: Completeness of the Gaia-verse II: what are the odds that a star is missing from Gaia DR2?

Authors: Douglas Boubert, Andrew Everall

Comments: 18 pages, re-submitted to MNRAS after the first round of comments. The Completeness of the Gaia-verse project website can be found at this http URL and the selectionfunctions Python package can be found at this https URL

Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

The second data release of the Gaia mission contained astrometry and photometry for an incredible 1,692,919,135 sources, but how many sources did Gaia miss and where do they lie on the sky? The answer to this question will be crucial for any astronomer attempting to map the Milky Way with Gaia DR2. We infer the completeness of Gaia DR2 by exploiting the fact that it only contains sources with at least five astrometric detections. The odds that a source achieves those five detections depends on both the number of observations and the probability that an observation of that source results in a detection. We predict the number of times that each source was observed by Gaia and assume that the probability of detection is either a function of magnitude or a distribution as a function of magnitude. We fit both these models to the 1.7 billion stars of Gaia DR2, and thus are able to robustly predict the completeness of Gaia across the sky as a function of magnitude. We extend our selection function to account for crowding in dense regions of the sky, and show that this is vitally important, particularly in the Galactic bulge and the Large and Small Magellanic Clouds. We find that the magnitude limit at which Gaia is still 99% complete varies over the sky from $G=18.9$ to $21.3$. We have created a new Python package selectionfunctions (https://github.com/gaiaverse/selectionfunctions) which provides easy access to our selection functions.

[8]  arXiv:2005.08985 [pdf, ps, other]

Title: Diffuse LINER-type emission from extended disc regions of barred galaxies

Authors: S.M. Percival (1), P.A. James (1) ((1) ARI, Liverpool John Moores University)

Comments: 14 pages, 8 figures; accepted by MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a spectroscopic analysis of the central disc regions of barred spiral galaxies, concentrating on the region that is swept by the bar but not including the bar itself (the `Star Formation Desert' or SFD region). New spectroscopy is presented for 34 galaxies, and the full sample analysed comprises 48 SBa - SBcd galaxies. These data confirm the full suppression of star formation within the SFD regions of all but the latest type (SBcd) galaxies. However, diffuse [NII] and H alpha line emission is detected in all galaxies. The ubiquity and homogeneous properties of this emission from SBa - SBc galaxies favour post-Asymptotic Giant Branch (p-AGB) stars as the source of this line excitation, rather than extreme Blue Horizontal Branch stars. The emission-line ratios strongly exclude any contribution from recent star formation, but are fully consistent with recent population synthesis modelling of p-AGB emission by other authors, and favour excitation dominated by ambient gas of approximately solar abundance, rather than ejecta from the AGB stars themselves. The line equivalent widths are also larger than those observed in many fully passive (e.g. elliptical) galaxies, which may also be a consequence of a greater ambient gas density in the SFD regions.

[9]  arXiv:2005.08987 [pdf, other]

Title: SDSS-IV MaNGA: Spatially resolved star formation in barred galaxies

Authors: Amelia Fraser-McKelvie, Alfonso Aragón-Salamanca, Michael Merrifield, Karen Masters, Preethi Nair, Eric Emsellem, Katarina Kraljic, Dhanesh Krishnarao, Brett H. Andrews, Niv Drory, Justus Neumann

Comments: 14 pages, 6 figures, accepted for publication in MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Bars inhabit the majority of local-Universe disk galaxies and may be important drivers of galaxy evolution through the redistribution of gas and angular momentum within disks. We investigate the star formation and gas properties of bars in galaxies spanning a wide range of masses, environments, and star formation rates using the MaNGA galaxy survey. Using a robustly-defined sample of 684 barred galaxies, we find that fractional (or scaled) bar length correlates with the host's offset from the star-formation main sequence. Considering the morphology of the H$\alpha$ emission we separate barred galaxies into different categories, including barred, ringed, and central configurations, together with H$\alpha$ detected at the ends of a bar. We find that only low-mass galaxies host star formation along their bars, and that this is located predominantly at the leading edge of the bar itself. Our results are supported by recent simulations of massive galaxies, which show that the position of star formation within a bar is regulated by a combination of shear forces, turbulence and gas flows. We conclude that the physical properties of a bar are mostly governed by the existing stellar mass of the host galaxy, but that they also play an important role in the galaxy's ongoing star formation.

[10]  arXiv:2005.08992 [pdf, other]

Title: Deep Learning improves Radio Frequency Interference Classification

Authors: Alireza Vafaei Sadr, Bruce A. Bassett, Nadeem Oozeer, Yabebal Fantaye, Chris Finlay

Comments: 12 pages, 15 figures. Prepared for submission to MNRAS

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Flagging of Radio Frequency Interference (RFI) is an increasingly important challenge in radio astronomy. We present R-Net, a deep convolutional ResNet architecture that significantly outperforms existing algorithms -- including the default MeerKAT RFI flagger, and deep U-Net architectures -- across all metrics including AUC, F1-score and MCC. We demonstrate the robustness of this improvement on both single dish and interferometric simulations and, using transfer learning, on real data. Our R-Net model's precision is approximately $90\%$ better than the current MeerKAT flagger at $80\%$ recall and has a 35\% higher F1-score with no additional performance cost. We further highlight the effectiveness of transfer learning from a model initially trained on simulated MeerKAT data and fine-tuned on real, human-flagged, KAT-7 data. Despite the wide differences in the nature of the two telescope arrays, the model achieves an AUC of 0.91, while the best model without transfer learning only reaches an AUC of 0.67. We consider the use of phase information in our models but find that without calibration the phase adds almost no extra information relative to amplitude data only. Our results strongly suggest that deep learning on simulations, boosted by transfer learning on real data, will likely play a key role in the future of RFI flagging of radio astronomy data.

[11]  arXiv:2005.08995 [pdf, other]

Title: Observing Correlations Between Dark Matter Accretion and Galaxy Growth: I. Recent Star Formation Activity in Isolated Milky Way-Mass Galaxies

Authors: Christine O'Donnell, Peter Behroozi, Surhud More

Comments: 16 pages; submitted to MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA)

The correlation between fresh gas accretion onto haloes and galaxy star formation is critical to understanding galaxy formation. Different theoretical models have predicted different correlation strengths between halo accretion rates and galaxy star formation rates, ranging from strong positive correlations to little or no correlation. Here, we present a technique to observationally measure this correlation strength for isolated Milky Way-mass galaxies with $z < 0.123$. This technique is based on correlations between dark matter accretion rates and the projected density profile of neighbouring galaxies; these correlations also underlie past work with splashback radii. We apply our technique to both observed galaxies in the Sloan Digital Sky Survey as well as simulated galaxies in the UniverseMachine where we can test any desired correlation strength. We find that positive correlations between dark matter accretion and recent star formation activity are ruled out with $\gtrsim 85\%$ confidence. Our results suggest that star formation activity may not be correlated with fresh accretion for isolated Milky Way-mass galaxies at $z=0$ and that other processes, such as gas recycling, dominate further galaxy growth.

[12]  arXiv:2005.08998 [pdf, other]

Title: Lensing anomaly as a fingerprint of alternative scenarios to inflation

Authors: Guillem Domènech, Xingang Chen, Marc Kamionkowski, Abraham Loeb

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The smoothing effect of lensing to the CMB temperature power spectrum is, to some extent, degenerate with oscillatory modulations of the primordial power spectrum, in particular if the frequency is close to that of the acoustic peaks. We consider the possibility that the lensing anomaly reported by the latest Planck 2018 results may be hinting at an oscillatory modulation generated by a massive scalar field during an alternative scenario to inflation or by a sharp feature during inflation. We use the full TTTEEE+low E CMB likelihood from Planck to derive constraints on these two types of models. We obtain that in both cases the $A_L$ anomaly is mildly reduced to less than $2\sigma$. Moreover, we find that the oscillatory modulation generated during an alternative scenario presents the lowest value of $\chi^2$, with $\Delta\chi^2=-13$ compared to $\Lambda$CDM. Furthermore, the Akaike Information Criterion suggests that such an oscillation constitutes an attractive candidate since it has a value $\Delta{\rm AIC}=-5$ with respect to $\Lambda$CDM, comparable to the $A_L$ parameter. Interestingly, the matter bounce and radiation bounce scenarios are compatible with our results. We discuss how these models of oscillatory features can be tested with future observations.

[13]  arXiv:2005.09002 [pdf, other]

Title: Binary Neutron Star Merger Simulations with a Calibrated Turbulence Model

Authors: David Radice

Comments: 20 pages, 6 figures. Submitted to the special issue "Numerical Relativity and Gravitational Wave" of Symmetry

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

Magnetohydrodynamic (MHD) turbulence in neutron star (NS) merger remnants can impact their evolution and multimessenger signatures, complicating the interpretation of present and future observations. Due to the high Reynolds numbers and the large computational costs of numerical relativity simulations, resolving all the relevant scales of the turbulence will be impossible for the foreseeable future. Here, we adopt a method to include subgrid-scale turbulence in moderate resolution simulations by extending the large-eddy simulation (LES) method to general relativity (GR). We calibrate our subgrid turbulence model with results from very-high-resolution GRMHD simulations, and we use it to perform NS merger simulations and study the impact of turbulence. We find that turbulence has a quantitative, but not qualitative impact on the evolution of NS merger remnants, on their gravitational wave signatures, and on the outflows generated in binary NS mergers. Our approach provides a viable path to quantify uncertainties due to turbulence in NS mergers.

[14]  arXiv:2005.09008 [pdf, other]

Title: An Objective Bayesian Analysis of Life's Early Start and Our Late Arrival

Authors: David Kipping

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Life emerged on the Earth within the first quintile of its habitable window, but a technological civilization did not blossom until its last. Efforts to infer the rate of abiogenesis, based on its early emergence, are frustrated by the selection effect that if the evolution of intelligence is a slow process, then life's early start may simply be a prerequisite to our existence, rather than useful evidence for optimism. In this work, we interpret the chronology of these two events in a Bayesian framework, extending upon previous work by considering that the evolutionary timescale is itself an unknown that needs to be jointly inferred, rather than fiducially set. We further adopt an objective Bayesian approach, such that our results would be agreed upon even by those using wildly different priors for the rates of abiogenesis and evolution - common points of contention for this problem. It is then shown that the earliest microfossil evidence for life indicates that the rate of abiogenesis is at least 2.8 times more likely to be a typically rapid process, rather than a slow one. This modest limiting Bayes factor rises to 8.7 if we accept the more disputed evidence of C13 depleted zircon deposits (Bell et al. 2015). For intelligence evolution, it is found that a rare-intelligence scenario is slightly favored at 3:2 betting odds. Thus, if we re-ran Earth's clock, one should statistically favor life to frequently re-emerge, but intelligence may not be as inevitable.

[15]  arXiv:2005.09010 [pdf, other]

Title: The effect of differential accretion on the Gravitational Wave Background and the present day MBH Binary population

Authors: Magdalena S. Siwek, Luke Zoltan Kelley, Lars Hernquist

Comments: 14 pages, 7 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Massive black hole binaries (MBHBs) form as a consequence of galaxy mergers. However, it is still unclear whether they typically merge within a Hubble time, and how accretion may affect their evolution. These questions will be addressed by pulsar timing arrays (PTAs), which aim to detect the GW background (GWB) emitted by MBHBs during the last Myrs of inspiral. Here we investigate the influence of differential accretion on MBHB merger rates, chirp masses and the resulting GWB spectrum. We evolve a MBHB sample from the Illustris hydrodynamic cosmological simulation using semi-analytic models and for the first time self-consistently evolve their masses with binary accretion models. In all models, MBHBs coalesce with median total masses up to $1.5 \times 10^8 M_{\odot}$, up to $3-4$ times larger than in models neglecting accretion. In our model with the largest plausible impact, the median mass ratio of coalescing MBHBs increases by a factor $3.6$, the coalescence rate by $52.3\%$, and the GWB amplitude by a factor $4.0$, yielding a dimensionless GWB strain $A_{yr^{-1}} = 1 \times 10^{-15}$. Our model that favours accretion onto the primary MBH reduces the median mass ratio of coalescing MBHBs by a factor of $2.9$, and yields a GWB amplitude $A_{yr^{-1}} = 3.1 \times 10^{-16}$. This is nearly indistinguishable from our model neglecting accretion, despite higher MBHB masses at coalescence. \textbf{We further predict binary separation and mass ratio distributions of stalled MBHBs in the low-redshift universe, and find that these depend sensitively on binary accretion models. This presents the potential for combined EM and GW observational constraints on merger rates and accretion models of MBHB populations.}

[16]  arXiv:2005.09014 [pdf, other]

Title: Gemini Multi-Object Spectrograph Integral Field Unit Spectroscopy of the Double-peaked Broad Emission Line of a Red Active Galactic Nucleus

Authors: Dohyeong Kim, Myungshin Im, Minjin Kim, Luis C. Ho

Comments: 12 pages, 6 figures, 1 table, Published in ApJ

Journal-ref: 2020ApJ...894..126K

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

Galaxy mergers are expected to produce multiple supermassive black holes (SMBHs) in close-separation, but the detection of such SMBHs has been difficult. 2MASS J165939.7$+$183436 is a red active galactic nucleus (AGN) that is a prospective merging SMBH candidate owing to its merging features in Hubble Space Telescope imaging and double-peaked broad emission lines (BELs). Herein, we report a Gemini Multi-Object Spectrograph Integral Field Unit observation of a double-peaked broad H$\alpha$ line of 2MASS J165939.7$+$183436. Furthermore, we confirm the existence of two BEL peaks that are kinematically separated by 3000\,$\rm km\,s^{-1}$, with the SMBH of each BEL component weighing at $10^{8.92\pm0.06}\,M_{\rm \odot}$ and $10^{7.13\pm0.06}\,M_{\rm \odot}$, if they arise from independent BELs near the two SMBHs. The BEL components were not separated at $>0\farcs1$; however, under several plausible assumptions regarding the fitting of each spaxel, the two components are found to be spatially separated at $0\farcs085$ ($\sim250$\,pc). Different assumptions for the fitting can lead to a null ($< 0\farcs05$) or a larger spatial separation ($\sim0\farcs15$). Given the uncertainty regarding the spatial separation, various models, such as the disk emitter and multiple SMBH models, are viable solutions to explain the double BEL components. These results will promote future research for finding more multiple SMBH systems in red AGNs, and higher-resolution imaging validates these different models.

[17]  arXiv:2005.09016 [pdf, other]

Title: The local universe in the era of large surveys. I. Spectral classification of S0 galaxies

Authors: J. L. Tous, J. M. Solanes, J. D. Perea

Comments: Accepted for publication in MNRAS. 26 pages, 18 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

This is the first paper in a series devoted to review the main properties of galaxies designated S0 in the Hubble classification system. Our aim is to gather abundant and, above all, robust information on the most relevant physical parameters of this poorly-understood morphological type and their possible dependence on the environment that could later be used to assess their possible formation channel(s). The adopted approach combines the characterisation of the fundamental features of the optical spectra of $68{,}043$ S0 with heliocentric $z\lesssim 0.1$ with the exploration of a comprehensive set of their global attributes. A principal component analysis is used to reduce the huge number of dimensions of the spectral data to a low-dimensional space facilitating a bias-free machine-learning-based classification of the galaxies. This procedure has revealed that objects bearing the S0 designation consist, despite their similar morphology, of two separate sub-populations with statistically inconsistent physical properties. Compared to the absorption-dominated S0, those with significant nebular emission are, on average, somewhat less massive, more luminous with less concentrated light profiles, have a younger, bluer and metal-poorer stellar component, and avoid high-galaxy-density regions. Noteworthy is the fact that the majority of members of this latter class, which accounts for at least a quarter of the local S0 population, show star formation rates and spectral characteristics entirely similar to those seen in late spirals. Our findings suggest that star-forming S0 might be less rare than hitherto believed and raise the interesting possibility of identifying them with plausible progenitors of their quiescent counterparts.

[18]  arXiv:2005.09032 [pdf, other]

Title: Dark matter searches by the planned gamma-ray telescope GAMMA-400

Authors: Andrey E. Egorov, Nikolay P. Topchiev, Arkadiy M. Galper, Oleg D. Dalkarov, Alexey A. Leonov, Sergey I. Suchkov, Yuriy T. Yurkin

Comments: 25 pages, 7 figures, submitted to JCAP

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)

Our paper reviews the planned space-based gamma-ray telescope GAMMA-400 and evaluates in details its opportunities in the field of dark matter (DM) indirect searches. We estimated the GAMMA-400 mean sensitivity to the diphoton DM annihilation cross section in the Galactic center for DM particle masses in the range of 1-500 GeV. We obtained the sensitivity gain at least by 1.2-1.5 times (depending on DM particle mass) with respect to the expected constraints from 12 years of observations by Fermi-LAT for the case of Einasto DM density profile. The joint analysis of the data from both telescopes may yield the gain up to 1.8-2.3 times. Thus the sensitivity reaches the level of annihilation cross section $\langle \sigma v \rangle_{\gamma\gamma}(m_\chi = 100~\mbox{GeV}) \approx 10^{-28}$ cm$^3$/s. This will allow us to test the hypothesized narrow lines predicted by specific DM models, particularly the recently proposed pseudo-Goldstone boson DM model. We estimated the GAMMA-400 sensitivity to axion-like particle (ALP) parameters by a potential observation of the supernova explosion in the Local Group. This is very sensitive probe of ALPs reaching the level of ALP-photon coupling constant $g_{a\gamma} \sim 10^{-13}~\mbox{GeV}^{-1}$ for ALP masses $m_a \lesssim 1$ neV. We also calculated the sensitivity to ALPs by constraining the modulations in the spectra of the Galactic gamma-ray pulsars due to possible ALP-photon conversion. GAMMA-400 is expected to be more sensitive than the CAST helioscope for ALP masses $m_a \approx (1-10)$ neV reaching $g_{a\gamma}^{min} \approx 2 \cdot 10^{-11}~\mbox{GeV}^{-1}$. Other potentially interesting targets and candidates are briefly considered too.

[19]  arXiv:2005.09037 [pdf, other]

Title: A gap, shadows, spirals, streamers: SPHERE observations of binary-disk interactions in GG Tau A

Authors: M. Keppler, A. Penzlin, M. Benisty, R. van Boekel, T. Henning, R. G. van Holstein, W. Kley, A. Garufi, C. Ginski, W. Brandner, G. H.-M. Bertrang, A. Boccaletti, J. de Boer, M. Bonavita, S. Brown Sevilla, G. Chauvin, C. Dominik, M. Janson, M. Langlois, G. Lodato, A.-L. Maire, F. Ménard, E. Pantin, Ch. Pinte, T. Stolker, J. Szulágyi, P. Thebault, M. Villenave, A. Zurlo, P. Rabou, P. Feautrier, M. Feldt, F. Madec, F. Wildi

Comments: Accepted for publication in A&A

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

A large fraction of stars is found to be part of binary or higher-order multiple systems. The ubiquity of planets found around single stars raises the question if and how planets in binary systems may form. Protoplanetary disks are the birthplaces of planets, and their characterization is crucial in order to understand the planet formation process. Our aim is to characterize the morphology of the GG Tau A disk, one of the largest and most massive circumbinary disks, and trace evidence for binary-disk interactions. We obtained observations in polarized scattered light of GG Tau A using the SPHERE/IRDIS instrument in the H-band filter. We analyze the observed disk morphology and substructures. We run 2D hydrodynamical models simulating the evolution of the circumbinary ring over the lifetime of the disk. The disk, as well as the cavity and the inner region are highly structured with several shadowed regions, spiral structures, and streamer-like filaments, some of them detected for the first time. The streamer-like filaments appear to connect the outer ring with the northern arc. Their azimuthal spacing suggests that they may be generated by periodic perturbations by the binary, tearing off material from the inner edge of the outer disk once during each orbit. By comparing observations to hydrodynamical simulations we find that the main features, in particular the gap size, as well as the spiral and streamer filaments, can be qualitatively explained by the gravitational interactions of a binary with semi-major axis of $\sim$35 au on an orbit coplanar with the circumbinary ring.

[20]  arXiv:2005.09064 [pdf, other]

Title: Possible evidence of ongoing planet formation in AB Aurigae. A showcase of the SPHERE/ALMA synergy

Authors: A. Boccaletti, E. Di Folco, E. Pantin, A. Dutrey, S. Guilloteau, Y. W. Tang, V. Piétu, E. Habart, J. Milli, T. L. Beck, A.-L. Maire

Comments: accepted in Astronomy and Astrophysics, 8 pages, 5 figures

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Context. Planet formation is expected to take place in the first million years of a planetary system through various processes, which remain to be tested through observations. Aims. With the recent discovery, using ALMA, of two gaseous spiral arms inside the 120 au cavity and connected to dusty spirals, the famous protoplanetary disk around AB Aurigae presents a strong incentive for investigating the mechanisms that lead to giant planet formation. A candidate protoplanet located inside a spiral arm has already been claimed in an earlier study based on the same ALMA data. Methods. We used SPHERE at the Very Large Telescope (VLT) to perform near-infrared (IR) high-contrast imaging of AB Aur in polarized and unpolarized light in order to study the morphology of the disk and search for signs of planet formation. Results. SPHERE has delivered the deepest images ever obtained for AB Aur in scattered light. Among the many structures that are yet to be understood, we identified not only the inner spiral arms, but we also resolved a feature in the form of a twist in the eastern spiral at a separation of about 30 au. The twist of the spiral is perfectly reproduced with a planet-driven density wave model when projection effects are accounted for. We measured an azimuthal displacement with respect to the counterpart of this feature in the ALMA data, which is consistent with Keplerian motion on a 4-yr baseline. Another point sxce is detected near the edge of the inner ring, which is likely the result of scattering as opposed to the direct emission from a planet photosphere. We tentatively derived mass constraints for these two features. Conclusions. The twist and its apparent orbital motion could well be the first direct evidence of a connection between a protoplanet candidate and its manifestation as a spiral imprinted in the gas and dust distributions.

[21]  arXiv:2005.09071 [pdf, other]

Title: Time-delay measurement of MgII broad line response for the highly-accreting quasar HE 0413-4031: Implications for the MgII-based radius-luminosity relation

Authors: Michal Zajaček, Bożena Czerny, Mary Loli Martinez-Aldama, Mateusz Rałowski, Aleksandra Olejak, Swayamtrupta Panda, Krzysztof Hryniewicz, Marzena Śniegowska, Mohammad-Hassan Naddaf, Wojtek Pych, Grzegorz Pietrzyński, C. Sobrino Figaredo, Martin Haas, Justyna Średzińska, Magdalena Krupa, Agnieszka Kurcz, Andrzej Udalski, Marek Gorski, Marek Sarna

Comments: 39 pages (23 pages - Main text, 16 pages - Appendix), 21 figures, 14 tables; accepted for publication in the Astrophysical Journal

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)

We present the monitoring of the AGN continuum and MgII broad line emission for the quasar HE 0413-4031 ($z=1.38$) based on the six-year monitoring by the South African Large Telescope (SALT). We managed to estimate a time-delay of $302.6^{+28.7}_{-33.1}$ days in the rest frame of the source using seven different methods: interpolated cross-correlation function (ICCF), discrete correlation function (DCF), $z$-transformed DCF, JAVELIN, two estimators of data regularity (Von Neumann, Bartels), and $\chi^2$ method. This time-delay is below the value expected from the standard radius-luminosity relation. However, based on the monochromatic luminosity of the source and the SED modelling, we interpret this departure as the shortening of the time-delay due to the higher accretion rate of the source, with the inferred Eddington ratio of $\sim 0.4$. The MgII line luminosity of HE 0413-4031 responds to the continuum variability as $L_{\rm line}\propto L_{\rm cont}^{0.43\pm 0.10}$, which is consistent with the light-travel distance of the location of MgII emission at $R_{\rm out} \sim 10^{18}\,{\rm cm}$. Using the data of 10 other quasars, we confirm the radius-luminosity relation for broad MgII line, which was previously determined for broad H$\beta$ line for lower-redshift sources. In addition, we detect a general departure of higher-accreting quasars from this relation in analogy to H$\beta$ sample. After the accretion-rate correction of the light-travel distance, the MgII-based radius-luminosity relation has a small scatter of only $0.10$ dex.

[22]  arXiv:2005.09077 [pdf, ps, other]

Title: Broad-band X-ray observation of broad-line radio galaxy 3C 109

Authors: Sulov Chalise, Anne M. Lohfink, Erin Kara, Andy C. Fabian

Comments: 13 pages, 8 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

We present a study of the central engine in the broad-line radio galaxy 3C 109. To investigate the immediate surrounding of this accreting, supermassive black hole, we perform a multi-epoch broad-band spectral analysis of a joint NuSTAR/XMM observation (2017), an archival xmm observation (2005) and the 105-month averaged Swift-BAT data. We are able to clearly separate the spectrum into a primary continuum, neutral and ionized absorption, and a reflection component. The photon index of the primary continuum has changed since 2005 ($\Gamma = 1.61 \substack{+0.02 \\ -0.01} \rightarrow 1.54 \pm{0.02}$), while other components remain unchanged, indicative of minimal geometric changes to the central engine. We constrain the high-energy cutoff of 3C 109 (E$_{\text{cut}}= 49 \substack{+7 \\ -5}$\,keV ) for the first time. The reflector is found to be ionized (log $\xi$ = $2.3 \substack{+0.1 \\ -0.2}$) but no relativistic blurring is required by the data. SED analysis confirms the super-Eddington nature of 3C 109 initially ($\lambda_{Edd} >$ 2.09). However, we do not find any evidence for strong reflection (R = $0.18 \substack{+0.04 \\ -0.03}$) or a steep power law index, as expected from a super-Eddington source. This puts the existing virial mass estimate of 2 $\times 10^{8}$M$_{\odot}$ into question. We explore additional ways of estimating the Eddington ratio, some of which we find to be inconsistent with our initial SED estimate. We obtain a new black hole mass estimate of 9.3 $\times 10^{8}$M$_{\odot}$, which brings all Eddington ratio estimates into agreement and does not require 3C 109 to be super-Eddington.

[23]  arXiv:2005.09092 [pdf, other]

Title: The Effect of Seafloor Weathering on Planetary Habitability

Authors: John Chambers

Comments: Accepted for publication in the Astrophysical Journal

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Conventionally, a habitable planet is one that can support liquid water on its surface. Habitability depends on temperature, which is set by insolation and the greenhouse effect, due mainly to CO2 and water vapor. The CO2 level is increased by volcanic outgassing, and decreased by continental and seafloor weathering. Here, I examine the climate evolution of Earth-like planets using a globally averaged climate model that includes both weathering types. Climate is sensitive to the relative contributions of continental and seafloor weathering, even when the total weathering rate is fixed. Climate also depends strongly on the dependence of seafloor weathering on CO2 partial pressure. Both these factors are uncertain. Earth-like planets have two equilibrium climate states: (i) an ice-free state where outgassing is balanced by both weathering types, and (ii) an ice-covered state where outgassing is balanced by seafloor weathering alone. The second of these has not been explored in detail before. For some planets, neither state exists, and the climate cycles between ice-covered and ice-free states. For some other planets, both equilibria exist, and the climate depends on the initial conditions. Insolation increases over time due to stellar evolution, so a planet usually encounters the ice-covered equilibrium first. Such a planet will remain ice-covered, even if the ice-free state appears subsequently, unless the climate receives a large perturbation. The ice-covered equilibrium state covers a large fraction of phase space for Earth-like planets. Many planets conventionally assigned to a star's habitable zone may be rendered uninhabitable as a result.

[24]  arXiv:2005.09096 [pdf, other]

Title: Physical Conditions in Shocked Interstellar Gas Interacting with the Supernova Remnant IC 443

Authors: Adam M. Ritchey (Univ. of Washington), Edward B. Jenkins (Princeton Univ. Observatory), Steven R. Federman (Univ. of Toledo), Johnathan S. Rice (Univ. of Toledo), Damiano Caprioli (Univ. of Chicago), George Wallerstein (Univ. of Washington)

Comments: 88 pages, 27 figures, accepted for publication in ApJ

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the results of a detailed investigation into the physical conditions in interstellar material interacting with the supernova remnant IC 443. Our analysis is based on a comprehensive examination of high-resolution far-ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope of two stars behind IC 443. One of our targets (HD 43582) probes gas along the entire line of sight through the supernova remnant, while the other (HD 254755) samples material located ahead of the primary supernova shock front. We identify low velocity quiescent gas in both directions and find that the densities and temperatures in these components are typical of diffuse atomic and molecular clouds. Numerous high velocity components are observed in the absorption profiles of neutral and singly-ionized atomic species toward HD 43582. These components exhibit a combination of greatly enhanced thermal pressures and significantly reduced dust-grain depletions. We interpret this material as cooling gas in a recombination zone far downstream from shocks driven into neutral gas clumps. The pressures derived for a group of ionized gas components at high positive velocity toward HD 43582 are lower than those of the other shocked components, pointing to pressure inhomogeneities across the remnant. A strong very high velocity component near -620 km/s is seen in the absorption profiles of highly-ionized species toward HD 43582. The velocity of this material is consistent with the range of shock velocities implied by observations of soft thermal X-ray emission from IC 443. Moderately high-velocity gas toward HD 254755 may represent shocked material from a separate foreground supernova remnant.

[25]  arXiv:2005.09122 [pdf, ps, other]

Title: Anchored in Shadows: Tying the Celestial Reference Frame Directly to Black Hole Event Horizons

Authors: T. M. Eubanks

Comments: Accepted for publication in the proceedings of the XXXIII General Assembly and Scientific Symposium (GASS) of the International Union of Radio Science(Union Radio Scientifique Internationale-URSI)

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Both the radio International Celestial Reference Frame (ICRF) and the optical Gaia Celestial Reference Frame (Gaia-CRF2) are derived from observations of jets produced by the Super Massive Black Holes (SMBH) powering active galactic nuclei and quasars. These jets are inherently subject to change and will appear different at different observing frequencies, leading to instabilities and systematic errors in the resulting Celestial Reference Frames (CRFs). Recently, the Event Horizon Telescope (EHT), a mm-wave Very Long Baseline Interferometry (VLBI) array, has observed the 40 micro-as diameter shadow of the SMBH in M87 at 1.3 mm, showing that the emitting region is smaller than the black-hole shadow. Use of these SMBH "emission rings" (and the associated photon rings) as astrometric references will enable the resulting CRF to be anchored directly in SMBH shadows; the ultimate reference points for any CRF for the forseeable future. A properly equipped space VLBI mission devoted to the observation of SMBH event horizons could lead to a two-orders-of-magnitude improvement in the accuracy and stabilty of the ICRF in the relatively near future.

[26]  arXiv:2005.09131 [pdf, other]

Title: Connecting the local stellar halo and its dark matter density to dwarf galaxies via blue stragglers

Authors: Luca Casagrande (Australian National University)

Comments: ApJ accepted. Video of Figure 1 at this https URL

Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Solar and Stellar Astrophysics (astro-ph.SR)

The Gaia HR diagram shows the presence of apparently young stars at high tangential velocities. Using a simple analytical model I show that these stars are likely to be blue stragglers. Once normalized to red giant stars, the fraction of nearby halo blue stragglers is of order 20 percent, and remarkably close to that measured in dwarf galaxies. Motivated by this similarity, I apply to field blue stragglers scaling relations inferred from blue stragglers in dwarf galaxies. Doing this for the Milky Way halo returns an average stellar density of 3.4 x 10^-5 Msun/pc^3 and a dark matter density of ~0.006 Msun/pc^3 ~ 0.22 GeV/cm^3 within 2 kpc from the Sun. These values compare favourably to other determinations available in the literature, but are based on an independent set of assumptions. A few considerations of this methodology are discussed, most notably that the correlation between the dark matter halo core-density and stellar mass seen in dwarf galaxies seems to hold also for the nearby Milky Way halo.

[27]  arXiv:2005.09132 [pdf, other]

Title: An Analytic Model for an Evolving Protoplanetary Disk with a Disk Wind

Authors: John Chambers

Comments: Published in the Astrophysical Journal

Journal-ref: The Astrophysical Journal, Volume 879, Issue 2, article id. 98, 11 pp. (2019)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We describe an analytic model for an evolving protoplanetary disk driven by viscosity and a disk wind. The disk is heated by stellar irradiation and energy generated by viscosity. The evolution is controlled by 3 parameters: (i) the inflow velocity towards the central star at a reference distance and temperature, (ii) the fraction of this inflow caused by the disk wind, and (iii) the mass loss rate via the wind relative to the inward flux in the disk. The model gives the disk midplane temperature and surface density as a function of time and distance from the star. It is intended to provide an efficient way to calculate conditions in a protoplanetary disk for use in simulations of planet formation. In the model, disks dominated by viscosity spread radially while losing mass onto the star. Radial spreading is the main factor reducing the surface density in the inner disk. The disk mass remains substantial at late times. Temperatures in the inner region are high at early times due to strong viscous heating. Disks dominated by a wind undergo much less radial spreading and weaker viscous heating. These disks have a much lower mass at late times than purely viscous disks. When mass loss via a wind is significant, the surface density gradient in the inner disk becomes shallower, and the slope can become positive in extreme cases.

[28]  arXiv:2005.09149 [pdf, other]

Title: A Universal fundamental plane and the $M_{dyn}-M_{\star}$ relation for galaxies with CALIFA and MaNGA

Authors: E. Aquino-Ortíz, S.F. Sánchez, O. Valenzuela, H. Hernández-Toledo, Yunpeng Jin, Ling Zhu, Glenn van de Ven, J.K. Barrera-Ballesteros, V. Avila-Reese, A. Rodríguez-Puebla, Patricia B. Tissera

Comments: Submitted to ApJ. 21 pages, 12 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We use the stellar kinematics for $2458$ galaxies from the MaNGA survey to explore dynamical scaling relations between the stellar mass $M_{\star}$ and the total velocity parameter at the effective radius, $R_e$, defined as $S_{K}^{2}=KV_{R_e}^{2}+\sigma_{\star_e}^{2}$, which combines rotation velocity $V_{R_e}$, and velocity dispersion $\sigma_{\star_e}$. We confirm that spheroidal and spiral galaxies follow the same $M_{\star}-S_{0.5}$ scaling relation with lower scatter than the $M_{\star}-V_{R_e}$ and $M_{\star}-\sigma_{\star_e}$ ones. We also explore a more general Universal Fundamental Plane described by the equation $log(\Upsilon_{e}) = log (S_{0.5}^{2}) - log (I_{e}) - log (R_{e}) + C$, which in addition to kinematics, $S_{0.5}$, and effective radius, $R_e$, it includes surface brightness, $I_e$, and dynamical mass-to-light ratio, $\Upsilon_e$. We use sophisticated Schwarzschild dynamical models for a sub-sample of 300 galaxies from the CALIFA survey to calibrate the so called Universal Fundamental Plane. That calibration allows us to propose both: (i) a parametrization to estimate the difficult-to-measure dynamical mass-to-light ratio at the effective radius; and (ii) a new dynamical mass proxy consistent with dynamical models within $0.09\ dex$. We reproduce the relation between the dynamical mass and the stellar mass in the inner regions of galaxies. We use the estimated dynamical mass-to-light ratio from our analysis, $\Upsilon_{e}^{fit}$, to explore the Universal Fundamental Plane with the MaNGA data set. We find that all classes of galaxies, from spheroids to disks, follow this Universal Fundamental Plane with a scatter significantly smaller $(0.05\ dex)$ than the one reported for the $M_{\star}-S_{0.5}$ relation $(0.1\ dex)$, the Fundamental Plane $(\sim 0.09\ dex)$ and comparable with Tully-Fisher studies $(\sim 0.05\ dex)$, but for a wider range of galaxy types.

[29]  arXiv:2005.09171 [pdf, other]

Title: An in-depth investigation of 11 pulsars discovered by FAST

Authors: A. D. Cameron, D. Li, G. Hobbs, L. Zhang, C. C. Miao, J. B. Wang, M. Yuan, S. Wang, G. Jacobs Corban, M. Cruces, S. Dai, Y. Feng, J. Han, J. F. Kaczmarek, J. R. Nui, Z. C. Pan, L. Qian, Z. Z. Tao, P. Wang, S. Q. Wang, H. Xu, R. X. Xu, Y. L. Yue, S. B. Zhang, Q. J. Zhi, W. W. Zhu, D. J. Champion, M. K. Kramer, S. Q. Zhou, K. P. Qiu, M. Zhu

Comments: 18 pages, 8 figures, 5 tables. Accepted for publication by MNRAS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present timing solutions and analyses of 11 pulsars discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These pulsars were discovered using an ultra-wide bandwidth receiver in drift-scan observations made during the commissioning phase of FAST, and were then confirmed and timed using the 64-m Parkes Radio Telescope. Each pulsar has been observed over a span of at least one year. Highlighted discoveries include PSR J0344-0901, which displays mode-changing behaviour and may belong to the class of so-called `swooshing' pulsars (alongside PSRs B0919+06 and B1859+07); PSR J0803-0942, whose emission is almost completely linearly polarised; and PSRs J1900-0134 and J1945+1211, whose well defined polarisation angle curves place stringent constraints on their emission geometry. We further discuss the detectability of these pulsars by earlier surveys, and highlight lessons learned from our work in carrying out confirmation and monitoring observations of pulsars discovered by a highly sensitive telescope, many of which may be applicable to next-generation pulsar surveys. This paper marks one of the first major releases of FAST-discovered pulsars, and paves the way for future discoveries anticipated from the Commensal Radio Astronomy FAST Survey (CRAFTS).

[30]  arXiv:2005.09179 [pdf, other]

Title: Spectropolarimetric follow-up of 8 rapidly rotating, X-ray bright FK Comae candidates

Authors: James Sikora, Jason Rowe, Steve Howell, Elena Mason, Gregg A. Wade

Comments: 15 pages, 12 figures. Accepted for publication in MNRAS

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Our understanding of the evolved, rapidly rotating, magnetically active, and apparently single FK Comae stars is significantly hindered by their extreme rarity: only two stars in addition to FK Com itself are currently considered to be members of this class. Recently, a sample of more than 20 candidate FK Comae type stars was identified within the context of the \emph{Kepler-Swift} Active Galaxies and Stars (KSwAGS) survey. We present an analysis of high-resolution Stokes $V$ observations obtained using ESPaDOnS@CFHT for 8 of these candidates. We found that none of these targets can be considered members of the FK Comae class based primarily on their inferred rotational velocities and on the detection of spectroscopic binary companions. However, 2 targets show evidence of magnetic activity and have anomalously high projected rotational velocities ($v\sin{i}$) relative to typical values associated with stars of similar evolutionary states. EPIC 210426551 has a $v\sin{i}=209\,{\rm km\,s}^{-1}$, an estimated mass of $1.07\,M_\odot$, and, based in part on its derived metallicity of ${\rm [M/H]}=-0.4$, it is either an evolved main sequence (MS) star or a pre-MS star. KIC 7732964 has a mass of $0.84\,M_\odot$, lies near the base of the red giant branch, and exhibits a $v\sin{i}=23\,{\rm km\,s}^{-1}$. We find that these two objects have similar characteristics to FK Com (albeit less extreme) and that their rapid rotation may be inconsistent with that predicted for a single star evolutionary history. Additional observations are necessary in order to better constrain their evolutionary states and whether they have short-period binary companions.

[31]  arXiv:2005.09187 [pdf, other]

Title: The Pulsation Properties of $λ$ Bootis Stars I. The Southern TESS Sample

Authors: S. J. Murphy, E. Paunzen, T. R. Bedding, P. Walczak, D. Huber

Comments: Accepted to MNRAS. 25 pages (main text 16 pages), including data tables and figures. Figures use colour liberally

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We analyse TESS light curves for 70 southern $\lambda$ Boo stars to identify binaries and to determine which of them pulsate as $\delta$ Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 percent of $\lambda$ Boo stars pulsate as $\delta$ Sct variables, which is about twice that of normal stars over the same parameter space. We determine the temperatures and luminosities of the $\lambda$ Boo stars from photometry and Gaia DR2 parallaxes. A subset of 40 $\lambda$ Boo stars have 2-min TESS data, reliable temperatures and luminosities, and $\delta$ Sct pulsation. We use Petersen diagrams (period ratios), \'echelle diagrams and the period--luminosity relation to identify the fundamental mode in 20 of those 40 stars and conclude that a further 8 stars are not pulsating in this mode. For the remaining 12, the fundamental mode cannot be unambiguously identified. Further mode identification is possible for 12 of the fundamental mode pulsators that have regular sequences of pulsation overtones in their \'echelle diagrams. We use stellar evolution models to determine statistically that the $\lambda$ Boo stars are only superficially metal weak. Simple pulsation models also better fit the observations at a metallicity of $Z=0.01$ than at $Z=0.001$. The TESS observations reveal the great potential of asteroseismology on $\lambda$ Boo stars, for determining precise stellar ages and shedding light on the origin(s) of the $\lambda$ Boo phenomenon.

[32]  arXiv:2005.09189 [pdf, ps, other]

Title: Evidence for a rapid decrease in Pluto's atmospheric pressure revealed by a stellar occultation in 2019

Authors: K Arimatsu, G. L. Hashimoto, M. Kagitani, T. Sakanoi, Y. Kasaba, R. Ohsawa, S. Urakawa

Comments: 7 pages, 3 figures, accepted for publication in Astronomy and Astrophysics

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We report observations of a stellar occultation by Pluto on 2019 July 17. A single-chord high-speed (time resolution $= 2\,$s) photometry dataset was obtained with a CMOS camera mounted on the Tohoku University 60 cm telescope (Haleakala, Hawaii). The occultation light curve is satisfactorily fitted to an existing Pluto's atmospheric model. We find the lowest pressure value at a reference radius of $r = 1215~{\rm km}$ among those reported after 2012, indicating a possible rapid (approximately $21^{+4}_{-5} \%$ of the previous value) pressure drop between 2016 (the latest reported estimate) and 2019. However, this drop is detected at a $2.4\sigma$ level only and still requires confirmation from future observations. If real, this trend is opposite to the monotonic increase of Pluto's atmospheric pressure reported by previous studies. The observed decrease trend is possibly caused by ongoing ${\rm N_2}$ condensation processes in the Sputnik Planitia glacier associated with an orbitally driven decline of solar insolation, as predicted by previous theoretical models. However, the observed amplitude of the pressure decrease is larger than the model predictions.

[33]  arXiv:2005.09227 [pdf, other]

Title: New measures to test modified gravity cosmologies

Authors: Jiro Matsumoto, Teppei Okumura, Misao Sasaki

Comments: 16 pages, 8 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

The observed accelerated expansion of the Universe may be explained by dark energy or the breakdown of general relativity (GR) on cosmological scales. When the latter case, a modified gravity scenario, is considered, it is often assumed that the background evolution is the same as the $\Lambda$CDM model but the density perturbation evolves differently. In this paper, we investigate more general classes of modified gravity, where both the background and perturbation evolutions are deviated from those in the $\Lambda$CDM model. We introduce two phase diagrams, $\alpha{\rm-}f\sigma _8$ and $H{\rm-}f\sigma _8$ diagrams; $H$ is the expansion rate, $f\sigma_8$ is a combination of the growth rate of the Universe and the normalization of the density fluctuation which is directly constrained by redshift-space distortions, and $\alpha$ is a parameter which characterizes the deviation of gravity from GR and can be probed by gravitational lensing. We consider several specific examples of Horndeski's theory, which is a general scalar-tensor theory, and demonstrate how deviations from the $\Lambda$CDM model appears in the $\alpha{\rm-}f\sigma _8$ and $H{\rm-}f\sigma _8$ diagrams. The predicted deviations will be useful for future large-scale structure observations to exclude some of the modified gravity models.

[34]  arXiv:2005.09266 [pdf, other]

Title: The POlarised GLEAM Survey (POGS) II: Results from an All-Sky Rotation Measure Synthesis Survey at Long Wavelengths

Authors: C. J. Riseley, T. J. Galvin, C. Sobey, T. Vernstrom, S. V. White, X. Zhang, B. M. Gaensler, G. Heald, C. S. Anderson, T. M. O. Franzen, P. J. Hancock, N. Hurley-Walker, E. Lenc, C. L. Van Eck

Comments: Accepted for publication in PASA. Manuscript has 31 pages, 10 figures, 5 tables. Four Appendices are included in the ancillary material, showing further Figures, continuum spectra for a handful of selected sources, and RM spectra for all 517 sources. Also included in the ancillary material are the full extragalactic and known pulsar catalogues

Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The low-frequency linearly-polarised radio source population is largely unexplored. However, a renaissance in low-frequency polarimetry has been enabled by pathfinder and precursor instruments for the Square Kilometre Array. In this second paper from the POlarised GaLactic and Extragalactic All-Sky Murchison Widefield Array (MWA) Survey -- the POlarised GLEAM Survey, or POGS -- we present the results from our all-sky MWA Phase I Faraday Rotation Measure survey. Our survey covers nearly the entire Southern sky in the Declination range $-82^{\circ}$ to $+30^{\circ}$ at a resolution between around three and seven arcminutes (depending on Declination) using data in the frequency range 169$-$231 MHz. We have performed two targeted searches: the first covering 25,489 square degrees of sky, searching for extragalactic polarised sources; the second covering the entire sky South of Declination $+30^{\circ}$, searching for known pulsars. We detect a total of 517 sources with 200 MHz linearly-polarised flux densities between 9.9 mJy and 1.7 Jy, of which 33 are known radio pulsars. All sources in our catalogues have Faraday rotation measures in the range $-328.07$ rad m$^{-2}$ to $+279.62$ rad m$^{-2}$. The Faraday rotation measures are broadly consistent with results from higher-frequency surveys, but with typically more than an order of magnitude improvement in the precision, highlighting the power of low-frequency polarisation surveys to accurately study Galactic and extragalactic magnetic fields. We discuss the properties of our extragalactic and known-pulsar source population, how the sky distribution relates to Galactic features, and identify a handful of new pulsar candidates among our nominally extragalactic source population.

[35]  arXiv:2005.09273 [pdf, other]

Title: Hybrid star HD 81817 accompanied by brown dwarf or substellar companion

Authors: Tae-Yang Bang, Byeong-Cheol Lee, V. Perdelwitz, Gwanghui Jeong, Inwoo Han, Hyeong-Il Oh, Myeong-Gu Park

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

HD 81817 is known as a hybrid star. Hybrid stars have both cool stellar wind properties and Ultraviolet (UV) or even X-ray emission features of highly ionized atoms in their spectra. A white dwarf companion has been suggested as the source of UV or X-ray features. HD 81817 has been observed since 2004 as a part of a radial velocity (RV) survey program to search for exoplanets around K giant stars using the Bohyunsan Observatory Echelle Spectrograph at the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory in Korea. We obtained 85 RV measurements between 2004 and 2019 for HD 81817 and found two periodic RV variations. The amplitudes of RV variations are around 200 m s^-1, which are significantly lower than that expected from a closely orbiting white dwarf companion. Photometric data and relevant spectral lines were also analyzed to help determine the origin of the periodic RV variations. We conclude that 627.4-day RV variations are caused by intrinsic stellar activities such as long-term pulsations or rotational modulations of surface activities based on H{\alpha} equivalent width (EW) variations of a similar period. On the other hand, 1047.1-day periodic RV variations are likely to be caused by a brown dwarf or substellar companion, which is corroborated by a recent GAIA proper motion anomaly for HD 81817. The Keplerian fit yields a minimum mass of 27.1 M_Jup, a semimajor axis of 3.3 AU, and an eccentricity of 0.17 for the stellar mass of 4.3 M_sun for HD 81817. The inferred mass puts HD 81817 b in the brown dwarf desert.

[36]  arXiv:2005.09289 [pdf, other]

Title: Machine learning for gravitational-wave detection: surrogate Wiener filtering for the prediction and optimized cancellation of Newtonian noise at Virgo

Authors: F Badaracco, J Harms, A Bertolini, T Bulik, I Fiori, B Idzkowski, A Kutynia, K Nikliborc, F Paoletti, A Paoli, L Rei, M Suchinski

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The cancellation of noise from terrestrial gravity fluctuations, also known as Newtonian noise (NN), in gravitational-wave detectors is a formidable challenge. Gravity fluctuations result from density perturbations associated with environmental fields, e.g., seismic and acoustic fields, which are characterized by complex spatial correlations. Measurements of these fields necessarily provide incomplete information, and the question is how to make optimal use of available information for the design of a noise-cancellation system. In this paper, we present a machine-learning approach to calculate a surrogate model of a Wiener filter. The model is used to calculate optimal configurations of seismometer arrays for a varying number of sensors, which is the missing keystone for the design of NN cancellation systems. The optimization results indicate that efficient noise cancellation can be achieved even for complex seismic fields with relatively few seismometers provided that they are deployed in optimal configurations. In the form presented here, the optimization method can be applied to all current and future gravitational-wave detectors located at the surface and with minor modifications also to future underground detectors.

[37]  arXiv:2005.09312 [pdf, ps, other]

Title: Determination of accurate rest frequencies and hyperfine structure parameters of cyanobutadiyne, HC$_5$N

Authors: Thomas F. Giesen, Michael E. Harding, Jürgen Gauss, Jens-Uwe Grabow, Holger S. P. Müller

Comments: 9 pages; J. Mol. Spectrosc., accepted

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); Atomic and Molecular Clusters (physics.atm-clus); Chemical Physics (physics.chem-ph)

Very accurate transition frequencies of HC$_5$N were determined between 5.3 and 21.4 GHz with a Fourier transform microwave spectrometer. The molecules were generated by passing a mixture of HC$_3$N and C$_2$H$_2$ highly diluted in neon through a discharge valve followed by supersonic expansion into the Fabry-Perot cavity of the spectrometer. The accuracies of the data permitted us to improve the experimental $^{14}$N nuclear quadrupole coupling parameter considerably and the first experimental determination of the $^{14}$N nuclear spin-rotation parameter. The transition frequencies are also well suited to determine in astronomical observations the local speed of rest velocities in molecular clouds with high fidelity. The same setup was used to study HC$_7$N, albeit with modest improvement of the experimental $^{14}$N nuclear quadrupole coupling parameter. Quantum chemical calculations were carried out to determine $^{14}$N nuclear quadrupole and spin-rotation coupling parameters of HC$_5$N, HC$_7$N, and related molecules. These calculations included evaluation of vibrational and relativistic corrections to the non-relativistic equilibrium quadrupole coupling parameters; their considerations improved the agreement between calculated and experimental values substantially.

[38]  arXiv:2005.09316 [pdf, other]

Title: Modelling and peeling extended sources with shapelets: a Fornax A case study

Authors: J. L. B. Line (1 and 2), D. A. Mitchell (3), B. Pindor (4 and 2), J. L. Riding (4 and 2), B. McKinley (1 and 2), R. L. Webster (4 and 2), C. M. Trott (1 and 2), N. Hurley-Walker (1 and 2), A. R. Offringa (5) ((1) International Centre for Radio Astronomy Research, Curtin University, (2) ARC Centre of Excellence for All Sky Astrophysics in 3 Dimension (ASTRO 3D), (3) CSIRO Astronomy and Space Science (CASS), (4) The University of Melbourne, (5) Netherlands Institute for Radio Astronomy (ASTRON))

Comments: 17 pages, 11 Figures, accepted for publication in Publications of the Astronomical Society of Australia (18/05/2020). "For the SHAMFI code, see: this https URL" . "For the SHAMFI documentation, see: this https URL" . "For the WODEN code and documentation see: this https URL"

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

To make a power spectrum (PS) detection of the 21 cm signal from the Epoch of Reionisation (EoR), one must avoid/subtract bright foreground sources. Sources such as Fornax A present a modelling challenge due to spatial structures spanning from arc seconds up to a degree. We compare modelling with multi-scale (MS) CLEAN components to 'shapelets', an alternative set of basis functions. We introduce a new image-based shapelet modelling package, SHAMFI. We also introduce a new CUDA simulation code (WODEN) to generate point source, Gaussian, and shapelet components into visibilities. We test performance by modelling a simulation of Fornax A, peeling the model from simulated visibilities, and producing a residual PS. We find the shapelet method consistently subtracts large-angular-scale emission well, even when the angular-resolution of the data is changed. We find that when increasing the angular-resolution of the data, the MS CLEAN model worsens at large angular-scales. When testing on real MWA data, the expected improvement is not seen in real data because of the other dominating systematics still present. Through further simulation we find the expected differences to be lower than obtainable through current processing pipelines. We conclude shapelets are worthwhile for subtracting extended galaxies, and may prove essential for an EoR detection in the future, once other systematics have been addressed.

[39]  arXiv:2005.09360 [pdf]

Title: A trampoline effect occurring in the stages of planetary reseeding

Authors: Ian von Hegner

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Biological Physics (physics.bio-ph)

Impactors have hit the Earth ever since its formation and have continued to be infrequent guests throughout the Earth's history. Although the early part of the Earth's history was marked by these violent events, it is known that life was present early, possibly existing already in the Hadean Eon. It is possible that life can be, and still is, transported between the worlds of the solar system due to impacts leading material away from the impact region. In addition to this lithopanspermia theory, it has been suggested that ejected material can also return to its home planet and 'reseed' life after the world has recovered after a global impactor, thus restarting evolution, the so-called refugium hypothesis. Next to such impactors more frequent impacts from smaller non-sterilizing impactors existed during the Heavy Bombardment epoch, feeding material potentially harboring viable organisms into near Earth space. During the three stages of planetary reseeding the encapsulated bacterial population will experience abiotic stressors, specifically they will experience pressure and heat shock twice, in stage 1 and after a recovery phase in stage 2, again in stage 3.While many circumstances have played a role in lifes endurance in the early history of the Earth, a particular biological effect could potentially be conferred on a bacterial population in this scenario. Thus, the surviving population will not only experience an increase in the frequency of robust genotypes, but it can also be expected that their stress tolerance is enhanced compared to non-stressed organisms of the same species. Hence, the trampoline effect means that the mean robustness of the bacterial population towards these stressors is higher in stage 3, than at stage 1.In principle, the time between the impactor and the reimpactor need not be long before this trampoline effect appears.

[40]  arXiv:2005.09364 [pdf, other]

Title: Grain growth in newly discovered young eruptive stars

Authors: Á. Kóspál, P. Ábrahám, A. Carmona, L. Chen, J. D. Green, R. van Boekel, J. A. White

Comments: 7 pages, 1 table, 3 figures, accepted for publication in the Astrophysical Journal Letters

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

FU Orionis-type stars are young stellar objects showing large outbursts due to highly enhanced accretion from the circumstellar disk onto the protostar. FUor-type outbursts happen in a wide variety of sources from the very embedded ones to those with almost no sign of extended emission beyond the disk. The subsequent eruptions might gradually clear up the obscuring envelope material and drive the protostar on its way to become a disk-only T Tauri star. We used VLT/VISIR to obtain the first spectra that cover the 8-13 $\mu$m mid-infrared wavelength range in low-resolution of five recently discovered FUors. Four objects from our sample show the 10 $\mu$m silicate feature in emission. We study the shape and strength of the silicate feature in these objects and find that they mostly contain large amorphous grains, suggesting that large grains are typically not settled to the midplane in FUor disks. This is a general characteristic of FUors, as opposed to regular T Tauri-type stars whose disks display anything from pristine small grains to significant grain growth. We classify our targets by determining whether the silicate feature is in emission or in absorption, and confront them with the evolutionary scenarios on the dispersal of the envelopes around young stars. In our sample, all Class II objects exhibit silicate emission, while for Class I objects, the appearance of the feature in emission or absorption depends on the viewing angle with respect to the outflow cavity. This highlights the importance of geometric effects when interpreting the silicate feature.

[41]  arXiv:2005.09383 [pdf, ps, other]

Title: Star formation in outer rings of S0 galaxies. III. UGC 5936 -- an S0 with currently accreted satellite matter

Authors: Olga Sil'chenko, Alexei Moiseev

Comments: 5 pages, 5 figures, accepted for publication in A&A Letters

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Though S0 galaxies are usually thought to be `red and dead', they demonstrate often star formation organized in ring structures. We try to clarify the nature of this phenomenon and its difference from star formation in spiral galaxies. The luminous S0 galaxy with a large ring, UGC 5936, is studied here. By applying long-slit spectroscopy along the major axis of UGC 5936, we have measured gas and star kinematics, Lick indices for the main body of the galaxy, and strong emission-line flux ratios in the ring. After inspecting the gas excitation in the ring using line ratios diagnostic diagrams and having ensured that it is ionized mostly by young stars, we have determined the gas oxygen abundance by using popular strong-line methods. Also we have proved the spatial proximity of the south-eastern dwarf satellite to UGC 5936 and have measured its gas metallicity. The ionized gas of the ring is excited by young stars and has solar metallicity. Star formation in the ring is rather prolonged, and its intensity corresponds to the current HI content of UGC 5936 (to the Kennicutt-Schmidt relation). The whole morphology of the HI distribution implies current accretion of the cold gas from the satellite onto the outer disc of UGC 5936; due to the satellite location and rotation in the plane of the stellar disc of the host galaxy, the accretion is smooth and laminar providing the favorable condition for star formation ignition.

[42]  arXiv:2005.09387 [pdf, other]

Title: Exploring the evolution of stellar rotation using Galactic kinematics

Authors: Ruth Angus, Angus Beane, Adrian M. Price-Whelan, Elisabeth Newton, Jason L. Curtis, Travis Berger, Jennifer van Saders, Rocio Kiman, Daniel Foreman-Mackey, Yuxi Lu, Lauren Anderson, Jacqueline K. Faherty

Comments: Accepted for publication in the Astronomical Journal

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

The rotational evolution of cool dwarfs is poorly constrained after around 1-2 Gyr due to a lack of precise ages and rotation periods for old main-sequence stars. In this work we use velocity dispersion as an age proxy to reveal the temperature-dependent rotational evolution of low-mass Kepler dwarfs, and demonstrate that kinematic ages could be a useful tool for calibrating gyrochronology in the future. We find that a linear gyrochronology model, calibrated to fit the period-Teff relationship of the Praesepe cluster, does not apply to stars older than around 1 Gyr. Although late-K dwarfs spin more slowly than early-K dwarfs when they are young, at old ages we find that late-K dwarfs rotate at the same rate or faster than early-K dwarfs of the same age. This result agrees qualitatively with semi-empirical models that vary the rate of surface-to-core angular momentum transport as a function of time and mass. It also aligns with recent observations of stars in the NGC 6811 cluster, which indicate that the surface rotation rates of K dwarfs go through an epoch of inhibited evolution. We find that the oldest Kepler stars with measured rotation periods are late-K and early-M dwarfs, indicating that these stars maintain spotted surfaces and stay magnetically active longer than more massive stars. Finally, based on their kinematics, we confirm that many rapidly rotating GKM dwarfs are likely to be synchronized binaries.

[43]  arXiv:2005.09388 [pdf, ps, other]

Title: Pulsar glitch detection with a hidden Markov model

Authors: A. Melatos, L. M. Dunn, S. Suvorova, W. Moran, R. J. Evans

Comments: Accepted for publication in The Astrophysical Journal

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Pulsar timing experiments typically generate a phase-connected timing solution from a sequence of times-of-arrival (TOAs) by absolute pulse numbering, i.e. by fitting an integer number of pulses between TOAs in order to minimize the residuals with respect to a parametrized phase model. In this observing mode, rotational glitches are discovered, when the residuals of the no-glitch phase model diverge after some epoch, and glitch parameters are refined by Bayesian follow-up. Here an alternative, complementary approach is presented which tracks the pulse frequency $f$ and its time derivative $df/dt$ with a hidden Markov model (HMM), whose dynamics include stochastic spin wandering (timing noise) and impulsive jumps in $f$ and $df/dt$ (glitches). The HMM tracks spin wandering explicitly, as a specific realization of a discrete-time Markov chain. It discovers glitches by comparing the Bayes factor for glitch and no-glitch models. It ingests standard TOAs for convenience and, being fully automated, allows performance bounds to be calculated quickly via Monte Carlo simulations. Practical, user-oriented plots are presented of the false alarm probability and detection threshold (e.g. minimum resolvable glitch size) versus observational scheduling parameters (e.g. TOA uncertainty, mean delay between TOAs) and glitch parameters (e.g. transient and permanent jump sizes, exponential recovery time-scale). The HMM is also applied to $\sim 1$ yr of real data bracketing the 2016 December 12 glitch in PSR J0835-4510 as a proof of principle. It detects the known glitch and confirms that no other glitch exists in the same data with size $> 10^{-7} f$.

[44]  arXiv:2005.09410 [pdf, other]

Title: A discrete chemo-dynamical model of M87's globular clusters: Kinematics extending to ~ 400 kpc

Authors: Chao Li, Ling Zhu, R. J. Long, Shude Mao, Eric W. Peng, Marc Sarzi, Glenn van de Ven, Hongxin Zhang, Rui Guo, Xiangxiang Xue, Alessia Longobardi, Patrick Côté, Laura Ferrarese, Chengze Liu, Stephen Gwyn, Sungsoon Lim, Youkyung Ko

Journal-ref: MNRAS, 2020, 492(2):2775-2795

Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the mass distribution and kinematics of the giant elliptical galaxy M87 (NGC 4486) using discrete chemo-dynamical, axisymmetric Jeans equation modelling. Our catalogue comprises 894 globular clusters (GCs) extending to a projected radius of $\sim 430$ kpc with line-of-sight velocities and colours, and Multi Unit Spectroscopic Explorer (MUSE) integral field unit data within the central $2.4$ kpc of the main galaxy. The gravitational potential for our models is a combination of a luminous matter potential with a varying mass-to-light ratio for the main galaxy, a supermassive black hole and a dark matter (DM) potential with a cusped or cored DM halo. The best-fitting models with either a cusped or a cored DM halo show no significant differences and both are acceptable. We obtain a total mass of $(2.16 \pm 0.38) \times 10^{13} M_{\odot}$ within $\sim$ 400 kpc. By including the stellar mass-to-light ratio gradient, the DM fraction increases from $\sim$ 26 percent (with no gradient) to $\sim$ 73 percent within $1\,R_e^{\rm maj}$ (major axis of half-light isophote, 14.2 kpc), and from $\sim$ 84 percent to $\sim$ 94 percent within $5\,R_e^{\rm maj}$ (71.2 kpc). Red GCs have moderate rotation with $V_{\rm max}/\sigma \sim$ 0.4, and blue GCs have weak rotation with $V_{\rm max}/\sigma \sim$ 0.1. Red GCs have tangential velocity dispersion anisotropy, while blue GCs are consistent with being nearly isotropic. Our results suggest that red GCs are more likely to be born in-situ, while blue GCs are more likely to be accreted.

[45]  arXiv:2005.09419 [pdf, ps, other]

Title: Interferometric Imaging with LOFAR Remote Baselines of the Fine Structures of a Solar Type IIIb Radio Burst

Authors: PeiJin Zhang, Pietro Zucca, Sarrvesh Seethapuram Sridhar, ChuanBing Wang, Diana E. Morosan, Bartosz Dabrowski, Andrzej Krankowski, Mario M. Bisi, Jasmina Magdalenic, Christian Vocks, Gottfried Mann

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Context. Solar radio bursts originate mainly from high energy electrons accelerated in solar eruptions like solar flares, jets, and coronal mass ejections. A subcategory of solar radio bursts with short time duration may be used as a proxy to understand the wave generation and propagation within the corona. Aims. Complete case studies of the source size, position and kinematics of short term bursts are very rare due to instrumental limitations. A comprehensive multi-frequency spectroscopic and imaging study was carried out of a clear example of a solar type IIIb-III pair. Methods. In this work, the source of the radio burst was imaged with the interferometric mode, using the remote baselines of the LOw Frequency ARray (LOFAR). A detailed analysis of the fine structures in the spectrum and of the radio source motion with imaging was conducted. Results. The study shows how the fundamental and harmonic components have a significantly different source motion. The apparent source of the fundamental emission at 26.56MHz displaces away from the solar disk center at about 4 times the speed of light, while the apparent source of the harmonic emission at the same frequency shows a speed of < 0.02c. The source size of the harmonic emission, observed in this case, is smaller than that in previous studies, indicating the importance of the use of the remote baselines.

[46]  arXiv:2005.09441 [pdf, other]

Title: Redshift Evolution of the Underlying Type Ia Supernova Stretch Distribution

Authors: N. Nicolas, M. Rigault, Y. Copin, R. Graziani, G. Aldering, M. Briday, J. Nordin, Y.-L. Kim, S. Perlmutter

Comments: 9 pages, 7 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The true nature of type Ia supernovae (SNe Ia) remains largely unknown, and as survey statistics increase, the question of astrophysical systematic uncertainties rises, notably that of the SN Ia population evolution. In this paper, we study the dependence with redshift of the SN Ia SALT2.4 lightcurve stretch, a purely intrinsic SN property, to probe its potential redshift drift. The SN stretch has been shown to strongly correlate with the SN environment, notably with stellar age tracers. We model the underlying stretch distribution as a function of redshift, using the evolution of fraction of young and old SNe Ia as predicted by Rigault et al. (2018), and assuming constant underlying stretch distribution for each age population made of Gaussian mixtures. We test our prediction against published samples chosen to have negligible magnitude selection effects, so that any observed change is indeed of astrophysical and not observational origin. We clearly demonstrate that the underlying SN Ia stretch distribution is evolving as a function of redshift, and that the young/old drifting model is a much better description of the data than any time-constant model, including the sample-based asymmetric distributions usually used to correct Malmquist bias. The favored underlying stretch model is the bimodal one derived from Rigault et al. (2018): a high-stretch mode shared by both young and old environments, and a low-stretch mode exclusive to old environments. The precise impact of the redshift evolution of the SN Ia population intrinsic properties on cosmology remains to be studied. Yet,the astrophysical drift of the SN stretch distribution does affect current Malmquist bias corrections and thereby distances derived from SN affected by selection effects. We highlight that such a bias will increase with surveys covering increasingly larger redshift ranges, which is particularly important for LSST.

[47]  arXiv:2005.09457 [pdf, other]

Title: The Proper Motion of the Central Compact Object RX J0822-4300 in the Supernova Remnant Puppis A, Revisited

Authors: Martin Mayer (MPE), Werner Becker (MPE and MPIfR), Daniel Patnaude (SAO), P. Frank Winkler (Middlebury College), Ralph Kraft (SAO)

Comments: 15 pages, 7 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We present an improved proper motion measurement of the central compact object RX J0822-4300, located in the supernova remnant Puppis A. By employing a new data set taken in February 2019 by the High Resolution Camera aboard the Chandra X-ray Observatory, we approximately double the available temporal baseline for our analysis to slightly more than 19 years (7000 days). We correct for the astrometric inaccuracy of Chandra using calibrator stars with known optical positions that are detected in all observations. Thereby, we obtain absolute positions of RX J0822-4300 accurate to around 0.1'' and from these a new best estimate for its total proper motion of $\mu_{\rm tot}= (80.4 \pm 7.7)\,\rm{mas\,yr}^{-1}$. For a remnant distance of 2 kpc, this corresponds to a projected kick velocity of $(763 \pm 73)\, \rm{km\,s}^{-1}$ at a position angle of $\phi_0 = (247.8 \pm 4.4)^{\circ}$. The proper motion measurement of RX J0822-4300 is used for discussing the kinematic age of Puppis A.

[48]  arXiv:2005.09473 [pdf, other]

Title: CO+ first-negative band emission: A tracer for CO in the Martian upper atmosphere

Authors: Susarla Raghuram, Anil Bhardwaj

Comments: 7 pages and 5 figures

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Space Physics (physics.space-ph)

Recently, Imaging Ultraviolet Spectrograph (IUVS) on-board Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite observed CO$^+$ first-negative band limb emission in the Martian upper atmosphere. We aim to explore the photochemical processes in the Martian upper atmosphere, which drives this band emission. A photochemical model is developed to study the excitation processes of CO$^+$ first-negative band emission (B$^2\Sigma^+ \rightarrow$ X$^2\Sigma^+$) in the upper atmosphere of Mars. The number density profiles of CO$_2$ and CO from two different models, viz., Mars Climate Database (MCD) and Mars Global Ionosphere-Thermosphere (MGIT) are used to determining the limb intensity of this band emission. On increasing the CO density by a factor of 4 and 8 in MCD and MGIT models, respectively, the modelled CO$^+$ first-negative band limb intensity profile is found to be consistent with IUVS/MAVEN observation. In this case, the intensity of this band emission is significantly determined by the ionization of CO by solar photons and photoelectrons, and the role of dissociative ionization of CO$_2$ is negligible. Since CO is the major source of the CO$^+$(B$^2\Sigma^+$), we suggest that the observed CO$^+$ first-negative band emission intensity can be used to retrieve the CO density in the Martian upper atmosphere for the altitudes above 150 km.

[49]  arXiv:2005.09477 [pdf, other]

Title: Isomers in Interstellar Environments (I): The Case of Z- and E-Cyanomethanimine

Authors: Christopher N. Shingledecker, Germán Molpeceres, Víctor Rivilla, Liton Majumdar, Johannes Kästner

Comments: The Astrophysical Journal, accepted: 17 pages, 9 figures, 7 tables

Subjects: Astrophysics of Galaxies (astro-ph.GA); Chemical Physics (physics.chem-ph)

In this work, we present the results of our investigation into the chemistry of Z- and E-cyanomethanimine (HNCHCN), both of which are possible precursors to the nucleobase adenine. Ab initio quantum chemical calculations for a number of reactions with atomic hydrogen were carried out. We find that the reaction H + Z/E-HNCHCN leading both to H-addition as well as H$_2$-abstraction proceed via similar short-range barriers with bimolecular rate coefficients on the order of $\sim10^{-17}$ cm$^{3}$ s$^{-1}$. These results were then incorporated into astrochemical models and used in simulations of the giant molecular cloud G+0.693. The calculated abundances obtained from these models were compared with previous observational data and found to be in good agreement, with a predicted [Z/E] ratio of $\sim3$ - somewhat smaller than the previously derived value of $6.1\pm2.4$. We find that the [Z/E] ratio in our simulations is due mostly to ion-molecule destruction rates driven by the different permanent dipoles of the two conformers. Based on these results, we propose a general rule-of-thumb for estimating the abundances of isomers in interstellar environments.

[50]  arXiv:2005.09481 [pdf, other]

Title: A GPU Spatial Processing System for CHIME

Authors: Nolan Denman, Andre Renard, Keith Vanderlinde, Philippe Berger, Kiyoshi Masui, Ian Tretyakov, the CHIME Collaboration

Comments: To be submitted to JAI

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We present an overview of the GPU-based spatial processing system created for the Canadian Hydrogen Intensity Mapping Experiment (CHIME). The design employs AMD GPUs and readily-available consumer hardware in its processing nodes to provide a cost- and power-efficient processing substrate. These nodes are supported by a liquid-cooling system which allows continuous operation with modest power consumption and in all but the most adverse conditions. Capable of continuously correlating 2048 receiver-polarizations across 400 MHz of bandwidth, the CHIME X-engine constitutes the most powerful radio correlator currently in existence. The same system also provides formed-beam data products to commensal FRB and Pulsar experiments; it constitutes a general spatial-processing system of unprecedented scale and capability.

[51]  arXiv:2005.09493 [pdf, other]

Title: The Pacific Ocean Neutrino Experiment

Authors: M. Agostini, M. Böhmer, J. Bosma, K. Clark, M. Danninger, C. Fruck, R. Gernhäuser, A. Gärtner, D. Grant, F. Henningsen, K. Holzapfel, M. Huber, R. Jenkyns, C. B. Krauss, K. Krings, C. Kopper, K. Leismüller, S. Leys, P. Macoun, S. Meighen-Berger, J. Michel, R.W. Moore, M. Morley, P. Padovani, T. Pollmann, L. Papp, B. Pirenne, C. Qiu, I. C. Rea, E. Resconi, A. Round, A. Ruskey, C. Spannfellner, M. Traxler, A. Turcati, J. P. Yanez

Comments: 17 pages, 2 Figures, submitted to Nature Astronomy

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex)

The Pacific Ocean Neutrino Experiment (P-ONE) is a new initiative with a vision towards constructing a multi-cubic kilometre neutrino telescope, to expand our observable window of the Universe to highest energies, installed within the deep Pacific Ocean underwater infrastructure of Ocean Networks Canada.

[52]  arXiv:2005.09506 [pdf, ps, other]

Title: How Gaussian can the Sky be? Primordial Non-Gaussianity from Quantum Information

Authors: Cesar Gomez, Raul Jimenez

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)

Using the quantum information picture to describe the early universe as a time dependent quantum density matrix, with time playing the role of a stochastic variable, we compute the non-gaussian features in the distribution of primordial fluctuations. We use a quasi de Sitter model to compute the corresponding quantum Fisher information function as the second derivative of the relative entanglement entropy for the density matrix at two different times. We define the curvature fluctuations in terms of the time quantum estimator. Using standard quantum estimation theory we compute the non-gaussian features in the statistical distribution of primordial fluctuations. Our approach is model independent and only relies on the existence of a quasi de Sitter phase. We show that there are primordial non-gaussianities, both in the form of squeezed and equilateral shapes. The squeezed limit gives a value of $f_{\rm NL} \sim n_s-1$. In the equilateral limit we find that $f_{\rm NL} \sim 0.03$. The equilateral non-gaussianity is due to the non-linearity of Einstein's equation. On the other hand, the squeezed one is due to the quantum nature of clock synchronization and thus real and cannot be gauged away as a global curvature. We identify a new effect: {\it clock bias} which is a pure quantum effect and introduces a bias in the spectral tilt and running of the power spectrum of order $\sim 10^{-4}$, which could be potentially measurable and yield precious information on the quantum nature of the early Universe.

[53]  arXiv:2005.09553 [pdf, other]

Title: The physical properties of $Fermi$-4LAC flat spectrum radio quasars

Authors: Can Tan, Rui Xue, Lei-Ming Du, Shao-Qiang Xi, Ze-Rui Wang, Zhao-Hua Xie

Comments: Accepted for publication in ApJS

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

In this work, we collect quasi-simultaneous infrared, optical, X-ray and $\gamma$-ray data of 60 $Fermi$-4LAC flat spectrum radio quasars (FSRQs). In the framework of the conventional one-zone leptonic model, we investigate the physical properties of $Fermi$-4LAC FSRQs' jets by modeling their quasi-simultaneous spectral energy distributions (SEDs). Our main results are summarized as follows. (1) There is a linear correlation between synchrotron peak frequency and curvature of the electron energy distribution. As suggested by previous works, the slope of the best linear fitting equation of this correlation is consistent with statistic acceleration which needs a fluctuation of fractional acceleration gain. (2) The gamma-ray dissipation regions are located at the range from 0.1 to 10 pc away from the super-massive black hole, and located outside the broad-line region (BLR) and within the dusty torus (DT). (3) A size relation $P_{\rm e}$ (the kinetic power carried in relativistic electrons) $\sim$ $P_{\rm B}$ (Poynting flux) $\leq$ $P_{\rm r}$ (the radiative power ) $<$ $P_{\rm p}$ (the kinetic power in cold protons) is found in our modeling. Among them, $P_{\rm e}\sim P_{\rm B}$ suggests that SEDs of almost all FSRQs with parameters are close to equipartition between the magnetic field and the relativistic electrons. The $P_{\rm e} < P_{\rm r}$ suggest that the most energy of the relativistic electrons are dissipated by EC radiation for FSRQs. (4) There is an anti-correlation between the peak energy of SEDs ($\gamma_{\rm peak}$) and the jet power ($P_{\rm jet}$), which is consistent with the blazar sequence.

[54]  arXiv:2005.09555 [pdf, other]

Title: Gas-driven inspiral of binaries in thin accretion disks

Authors: Christopher Tiede, Jonathan Zrake, Andrew MacFadyen, Zoltan Haiman

Comments: 14 pages, 11 figures

Subjects: Astrophysics of Galaxies (astro-ph.GA)

Numerical studies of gas accretion onto supermassive black hole binaries (SMBHBs) have generally been limited to conditions where the circumbinary disk (CBD) is 10-100 times thicker than expected for disks in active galactic nuclei (AGN). This discrepancy arises from technical limitations, and also from publication bias toward replicating fiducial numerical models. Here we present the first systematic study of how the binary's orbital evolution varies with disk scale height. We report three key results: (1) Binary orbital evolution switches from outspiralling for warm disks (aspect ratio ~0.1), to inspiralling for more realistic cooler, thinner disks at a critical aspect ratio ~0.04, corresponding to orbital Mach number ~25. (2) The net torque on the binary arises from a competition between positive torque from gas orbiting close to the black holes, and negative torque from the inner edge of the CBD, which is denser for thinner disks. This leads to increasingly negative net torques on the binary for increasingly thin disks. (3) The accretion rate is modestly suppressed with increasing Mach number. We discuss how our results may influence modeling of the nano-Hz gravitational wave background, as well as estimates of the LISA merger event rate.

[55]  arXiv:2005.09574 [pdf, other]

Title: Model independent measurement of the growth rate from the consistency relations of the LSS

Authors: Marco Marinucci, Takahiro Nishimichi, Massimo Pietroni

Comments: 22 pages, 7 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The Consistency Relations for the Large Scale Structure provide a link between the amplitude of Baryonic Acoustic Oscillations in the squeezed bispectrum (BS) and in the power spectrum (PS). This relation depends on the large scale bias of the considered tracer, $b_\alpha$, and on the growth rate of structures, $f$. Remarkably, originating from basic symmetry principles, this relation is exact and independent on the underlying cosmological model.
By analysing data from large volume simulations, both for dark matter and for haloes, we illustrate how BS and PS measurements can be used to extract $b_\alpha$ and $f$ without the need of any theoretical approximation scheme for the computation of the BS and the PS. We show that, combining measurements of the squeezed BS with the quadrupole to monopole ratios for the PS at large scales can successfully break the $b_\alpha -f$ degeneracy. We forecast that this method, applied to a Euclid-like survey, will be able to measure bias, and then the growth rate, at better than $10\%$ level, with no extra assumption.

[56]  arXiv:2005.09586 [pdf, other]

Title: Development of a Confined Circular-cum-parallel Ribbon Flare and Associated Pre-flare Activity

Authors: Pooja Devi, Bhuwan Joshi, Ramesh Chandra, Prabir K. Mitra, Astrid M. Veronig3, Reetika Joshi

Comments: 24 pages, 11 figures, Accepted for publication in Solar Physics

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We study a complex GOES M1.1 circular ribbon flare and related pre-flare activity on 26 January 2015 [SOL26-01-2015] in solar active region NOAA 12268. This flare activity was observed by the AIA on board SDO and the RHESSI. The examination of photospheric magnetograms during the extended period, prior to the event, suggests the successive development of a so-called 'anemone' type magnetic configuration. NLFFF extrapolation reveals a fan-spine magnetic configuration with the presence of a coronal null-point. We found that the pre-flare activity in the active region starts ~15 min prior to the main flare in the form of localized bright patches at two locations. A comparison of locations and spatial structures of the pre-flare activity with magnetic configuration of the corresponding region suggests onset of magnetic reconnection at the null-point along with the low-atmosphere magnetic reconnection caused by the emergence and the cancellation of the magnetic flux. The main flare of M1.1 class is characterized by the formation of a well-developed circular ribbon along with a region of remote brightening. Remarkably, a set of relatively compact parallel ribbons formed inside the periphery of the circular ribbon which developed lateral to the brightest part of the circular ribbon. During the peak phase of the flare, a coronal jet is observed at the north-east edge of the circular ribbon which suggests interchange reconnection between large-scale field lines and low-lying closed field lines. Our investigation suggests a combination of two distinct processes in which ongoing pre-flare null-point reconnection gets further intensified as the confined eruption along with jet activity proceeded from within the circular ribbon region which results to the formation of inner parallel ribbons and corresponding post-reconnection arcade.

[57]  arXiv:2005.09613 [pdf, ps, other]

Title: Imaging and spectral study on the null point of a fan-spine structure during a solar flare

Authors: Shuhong Yang, Qingmin Zhang, Zhi Xu, Jun Zhang, Ze Zhong, Yang Guo

Comments: Accepted for publication in ApJ

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Using the multi-instrument observations, we make the first simultaneous imaging and spectral study on the null point of a fan-spine magnetic topology during a solar flare. When magnetic reconnection occurs at the null point, the fan-spine configuration brightens in the (extreme-)ultraviolet channels. In the H$\alpha$ images, the fan-spine structure is partly filled and outlined by the bi-directional material flows ejected from the reconnection site. The extrapolated coronal magnetic field confirms the existence of the fan-spine topology. Before and after the flare peak, the total velocity of the outflows is estimated to be about 60 km s$^{-1}$. During the flare, the Si IV line profile at the reconnection region is enhanced both in the blue-wing and red-wing. At the flare peak time, the total velocity of the outflows is found to be 144 km s$^{-1}$. Superposed on the Si IV profile, there are several deep absorption lines with the blueshift of several tens of km s$^{-1}$. The reason is inferred to be that the bright reconnection region observed in Si IV channel is located under the cooler material appearing as dark features in the H$\alpha$ line. The blueshifted absorption lines indicate the movement of the cooler material toward the observer. The depth of the absorption lines also depends on the amount of cooler material. These results imply that this kind of spectral profiles can be used as a tool to diagnose the properties of cooler material above reconnection site.

[58]  arXiv:2005.09615 [pdf, other]

Title: ARES II: Characterising the Hot Jupiters WASP-127 b, WASP-79 b and WASP-62 b with HST

Authors: Nour Skaf, Michelle Fabienne Bieger, Billy Edwards, Quentin Changeat, Mario Morvan, Flavien Kiefer, Doriann Blain, Tiziano Zingales, Mathilde Poveda, Ahmed Al-Refaie, Robin Baeyens, Amelie Gressier, Gloria Guilluy, Adam Yassin Jaziri, Darius Modirrousta-Galian, Lorenzo V. Mugnai, William Pluriel, Niall Whiteford, Sam Wright, Kai Hou Yip, Benjamin Charnay, Jeremy Leconte, Pierre Drossart, Angelos Tsiaras, Olivia Venot, Ingo Waldmann, Jean-Philippe Beaulieu

Comments: Accepted for publication in AJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

This paper presents the atmospheric characterisation of three large, gaseous planets: WASP-127 b, WASP-79 b and WASP-62 b. We analysed spectroscopic data obtained with the G141 grism (1.088 - 1.68 $\mu$m) of the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST) using the Iraclis pipeline and the TauREx3 retrieval code, both of which are publicly available. For WASP-127 b, which is the least dense planet discovered so far and is located in the short-period Neptune desert, our retrieval results found strong water absorption corresponding to an abundance of log(H$_2$O) = -2.71$^{+0.78}_{-1.05}$, and absorption compatible with an iron hydride abundance of log(FeH)=$-5.25^{+0.88}_{-1.10}$, with an extended cloudy atmosphere. We also detected water vapour in the atmospheres of WASP-79 b and WASP-62 b, with best-fit models indicating the presence of iron hydride, too. We used the Atmospheric Detectability Index (ADI) as well as Bayesian log evidence to quantify the strength of the detection and compared our results to the hot Jupiter population study by Tsiaras et al. 2018. While all the planets studied here are suitable targets for characterisation with upcoming facilities such as the James Webb Space Telescope (JWST) and Ariel, WASP-127 b is of particular interest due to its low density, and a thorough atmospheric study would develop our understanding of planet formation and migration.

[59]  arXiv:2005.09631 [pdf, other]

Title: Confirmation of water emission in the dayside spectrum of the ultrahot Jupiter WASP-121b

Authors: Thomas Mikal-Evans, David K. Sing, Tiffany Kataria, Hannah R. Wakeford, Nathan J. Mayne, Nikole K. Lewis, Joanna K. Barstow, Jessica J. Spake

Comments: Accepted in MNRAS

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present four new secondary eclipse observations for the ultrahot Jupiter WASP-121b acquired using the Hubble Space Telescope Wide Field Camera 3. The eclipse depth is measured to a median precision of 60ppm across 28 spectroscopic channels spanning the 1.12-1.64 micron wavelength range. This is a considerable improvement to the 90ppm precision we achieved previously for a single eclipse observation using the same observing setup. Combining these data with those reported at other wavelengths, a blackbody spectrum for WASP-121b is ruled out at >6-sigma confidence and we confirm the interpretation of previous retrieval analyses that found the data is best explained by a dayside thermal inversion. The updated spectrum clearly resolves the water emission band at 1.3-1.6 micron, with higher signal-to-noise than before. It also fails to reproduce a bump in the spectrum at 1.25 micron derived from the first eclipse observation, which had tentatively been attributed to VO emission. We conclude the latter was either a statistical fluctuation or a systematic artefact specific to the first eclipse dataset.

[60]  arXiv:2005.09632 [pdf, other]

Title: Markov Chains for Horizons (MARCH). I. Identifying Biases in Fitting Theoretical Models to Event Horizon Telescope Observations

Authors: Dimitrios Psaltis, Feryal Ozel, Lia Medeiros, Pierre Christian, Junhan Kim, Chi-kwan Chan, Landen J. Conway, Carolyn A. Raithel, Dan Marrone, Tod R. Lauer

Comments: ApJ, submitted

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We introduce a new Markov Chain Monte Carlo (MCMC) algorithm with parallel tempering for fitting theoretical models of horizon-scale images of black holes to the interferometric data from the Event Horizon Telescope (EHT). The algorithm implements forms of the noise distribution in the data that are accurate for all signal-to-noise ratios. In addition to being trivially parallelizable, the algorithm is optimized for high performance, achieving 1 million MCMC chain steps in under 20 seconds on a single processor. We use synthetic data for the 2017 EHT coverage of M87 that are generated based on analytic as well as General Relativistic Magnetohydrodynamic (GRMHD) model images to explore several potential sources of biases in fitting models to sparse interferometric data. We demonstrate that a very small number of data points that lie near salient features of the interferometric data exert disproportionate influence on the inferred model parameters. We also show that the preferred orientations of the EHT baselines introduce significant biases in the inference of the orientation of the model images. Finally, we discuss strategies that help identify the presence and severity of such biases in realistic applications.

[61]  arXiv:2005.09633 [pdf, ps, other]

Title: A New Metal-poor Globular Cluster and Resolved Stars in the Outer Disk of the Black Eye Galaxy M64: Implication for the Origin of the Type III Disk Break

Authors: Jisu Kang (1), Yoo Jung Kim (1), Myung Gyoon Lee (1), In Sung Jang (2) ((1) Seoul National University, (2) Leibniz-Institut fur Astrophysik Potsdam (AIP))

Comments: Accepted for publication in ApJ, 16 pages, 10 figures, 3 tables

Subjects: Astrophysics of Galaxies (astro-ph.GA)

M64 is a nearby spiral galaxy with a Type III anti-truncation component. To trace the origin of the Type III component, we present Hubble Space Telescope/Advanced Camera for Surveys $F606W/F814W$ photometry of resolved stars in a field located in the outer disk ($2.5' \lesssim r \lesssim 6.5'$) of M64. At $r\approx 5.5'$ (7 kpc) to the east, we discover a new metal-poor globular cluster ($R_{\rm eff}=5.73\pm0.02$ pc and $M_V=-9.54\pm0.09$ mag), M64-GC1. This is the first globular cluster found in M64. The color-magnitude diagram (CMD) of the resolved stars in M64-GC1 is well matched by 12 Gyr isochrones with [Fe/H] $=-1.5\pm0.2$, showing that this cluster belongs to a halo. The CMD of the resolved stars in the entire ACS field shows two distinguishable red giant branches (RGBs): a curved metal-rich RGB and a vertical metal-poor RGB. The metal-rich RGB represents an old metal-rich ([Fe/H] $\approx -0.4$) disk population. In contrast, the CMD of the metal-poor RGB stars is very similar to the CMD of M64-GC1, showing that the metal-poor RGB represents a halo population. The radial number density profile of the metal-rich RGB stars is described by an exponential disk law, while the profile of the metal-poor RGB stars is described by a de Vaucouleurs's law. From these, we conclude that the origin of the Type III component in M64 is a halo which has a much lower metallicity than a disk or bulge population.

Cross-lists for Wed, 20 May 20

[62]  arXiv:2005.09168 (cross-list from hep-ph) [pdf, other]

Title: Constraining sterile neutrinos by core-collapse supernovae with multiple detectors

Authors: Jian Tang, TseChun Wang, Meng-Ru Wu

Comments: 24 pages, 12 figures, 4 tables

Subjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

The eV-scale sterile neutrino has been proposed to explain some anomalous results in experiments, \textit{such as} the deficit of reactor neutrino fluxes and the excess of $\bar{\nu}_\mu\to\bar{\nu}_e$ in LSND. This hypothesis can be tested by future core-collapse supernova neutrino detection independently since the active-sterile mixing scheme affects the flavor conversion of neutrinos inside the supernova. In this work, we compute the predicted supernova neutrino events in future detectors -- DUNE, Hyper-K, and JUNO -- for neutrinos emitted during the neutronization burst phase when the luminosity of $\nu_e$ dominates the other flavors. We find that for a supernova occurring within 10 kpc, the difference in the event numbers with and without sterile neutrinos allows to exclude the sterile neutrino hypothesis at more than $99\%$ confidence level robustly. The derived constraints on sterile neutrinos mixing parameters are comparably better than the results from cosmology and on-going or proposed reactor experiments by more than two orders of magnitude in the $\sin^22\theta_{14}$-$\Delta m_{41}^2$ plane.

[63]  arXiv:2005.09232 (cross-list from physics.plasm-ph) [pdf, other]

Title: Statistics of Kinetic Dissipation in Earth's Magnetosheath -- MMS Observations

Authors: Riddhi Bandyopadhyay, William H. Matthaeus, Tulasi N. Parashar, Yan Yang, Alexandros Chasapis, Barbara L. Giles, Daniel J. Gershman, Craig J. Pollock, Christopher T. Russell, Robert J. Strangeway, Roy B. Torbert, Thomas E. Moore, James L. Burch

Comments: Accepted for publication in Physical Review Letters

Subjects: Plasma Physics (physics.plasm-ph); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

A familiar problem in space and astrophysical plasmas is to understand how dissipation and heating occurs. These effects are often attributed to the cascade of broadband turbulence which transports energy from large scale reservoirs to small scale kinetic degrees of freedom. When collisions are infrequent, local thermodynamic equilibrium is not established. In this case the final stage of energy conversion becomes more complex than in the fluid case, and both pressure-dilatation and pressure strain interactions (Pi-D $\equiv -\Pi_{ij} D_{ij}$) become relevant and potentially important. Pi-D in plasma turbulence has been studied so far primarily using simulations. The present study provides a statistical analysis of Pi-D in the Earth's magnetosheath using the unique measurement capabilities of the Magnetospheric Multiscale (MMS) mission. We find that the statistics of Pi-D in this naturally occurring plasma environment exhibit strong resemblance to previously established fully kinetic simulations results. The conversion of energy is concentrated in space and occurs near intense current sheets, but not within them. This supports recent suggestions that the chain of energy transfer channels involves regional, rather than pointwise, correlations.

[64]  arXiv:2005.09358 (cross-list from hep-ph) [pdf, ps, other]

Title: Magnetic helicity in plasma of chiral fermions electroweakly interacting with inhomogeneous matter

Authors: Maxim Dvornikov (IZMIRAN, Tomsk State University)

Comments: 14 pages in LaTeX2e, 1 eps figure, to be published in Nucl.Phys.B

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

We study chiral fermions electroweakly interacting with a background matter having the nonuniform density and the velocity arbitrarily depending on coordinates. The dynamics of this system is described approximately by finding the Berry phase. The effective action and the kinetic equations for right and left particles are derived. In the case of a rotating matter, we obtain the correction to the anomalous electric current and to the Adler anomaly. Then we study some astrophysical applications. Assuming that the chiral imbalance in a rotating neutron star vanishes, we obtain the rate of the magnetic helicity change owing to the interaction of chiral electrons with background neutrons. The characteristic time of the helicity change turns out to coincide with the period of the magnetic cycle of some pulsars.

[65]  arXiv:2005.09550 (cross-list from hep-th) [pdf, other]

Title: Analytic infinite derivative gravity, $R^2$-like inflation, quantum gravity and CMB

Authors: Alexey S. Koshelev, K. Sravan Kumar, Alexei A. Starobinsky

Comments: 6 pages, 3 figures, Received Honorable mention at the Gravity Research Foundation 2020 Awards for Essays on Gravitation

Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Emergence of $R^2$ inflation which is the best fit framework for CMB observations till date comes from the attempts to attack the problem of quantization of gravity which in turn have resulted in the trace anomaly discovery. Further developments in trace anomaly and different frameworks aiming to construct quantum gravity indicate an inevitability of non-locality in fundamental physics at small time and length scales. A natural question would be to employ the $R^2$ inflation as a probe for signatures of non-locality in the early Universe physics. Recent advances of embedding $R^2$ inflation in a string theory inspired non-local gravity modification provides very promising theoretical predictions connecting the non-local physics in the early Universe and the forthcoming CMB observations.

[66]  arXiv:2005.09618 (cross-list from nucl-th) [pdf, other]

Title: Transport in neutron star mergers

Authors: Steven P. Harris

Comments: Thesis, based on the works: arXiv:1705.09880, arXiv:1803.00662, arXiv:1907.03795, and arXiv:2003.09768

Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

After an introduction to the QCD phase diagram, the nuclear equations of state, and neutron star mergers, I discuss three projects related to transport and nuclear matter in neutron star mergers. The first is the nature of beta equilibrium in the portion of a merger that is transparent to neutrinos. We calculate the weak interaction (Urca) rates and find that the beta equilibrium condition needs to be modified by adding an additional chemical potential, which changes slightly the particle content in neutrino-transparent beta equilibrium. Secondly, we calculate the bulk viscosity in neutrino-transparent nuclear matter in conditions encountered in neutron star mergers. Bulk viscosity arises from a phase lag between the pressure and density in the nuclear matter, which is due to the finite rate of beta equilibration. When bulk viscosity is sufficiently strong, which happens when the equilibration rate nearly matches the frequency of the density oscillation, it can noticeably dampen the oscillation. We find that in certain thermodynamic conditions likely encountered in mergers, oscillations in nuclear matter can be damped on timescales on the order of 10 milliseconds, so we conclude that bulk viscosity should be included in merger simulations. Finally, we study thermal transport due to axions in neutron star mergers. We conclude that axions are never trapped in mergers, but instead escape, carrying energy away from the merger. We calculate the cooling time due to the energy carried away by axions and find that within current constraints on the axion-nucleon coupling, axions could cool fluid elements in mergers on timescales which could affect the dynamics of the merger.

Replacements for Wed, 20 May 20

[67]  arXiv:1507.02781 (replaced) [pdf, other]

Title: Impact of Galactic magnetic field modelling on searches of point sources via UHECR-Neutrino correlations

Authors: Jose Carpio, A.M. Gago

Comments: 8 pages, 4 figures, 3 tables; submitted to PRD

Journal-ref: Phys. Rev. D 93, 023004 (2016)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[68]  arXiv:1608.05099 (replaced) [pdf, other]

Title: A roadmap for searching cosmic rays correlated with the extraterrestrial neutrinos seen at IceCube

Authors: Jose Carpio, A.M. Gago

Comments: 6 pages, 5 figures

Journal-ref: Phys. Rev. D 95, 123009 (2017)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[69]  arXiv:1803.07967 (replaced) [pdf, other]

Title: Long-wavelength phonons in the crystalline and pasta phases of neutron-star crusts

Authors: David Durel, Michael Urban

Comments: 12 pages, 8 figures. mistakes in equations (27-30) corrected

Journal-ref: Phys. Rev. C 97, 065805 (2018)

Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)

[70]  arXiv:1901.00443 (replaced) [pdf, other]

Title: Stellar Flares from the First Tess Data Release: Exploring a New Sample of M-dwarfs

Authors: Maximilian N. Günther, Zhuchang Zhan, Sara Seager, Paul B. Rimmer, Sukrit Ranjan, Keivan G. Stassun, Ryan J. Oelkers, Tansu Daylan, Elisabeth Newton, Martti H. Kristiansen, Katalin Olah, Edward Gillen, Saul Rappaport, George R. Ricker, David W. Latham, Joshua N. Winn, Jon M. Jenkins, Ana Glidden, Michael Fausnaugh, Alan M. Levine, Jason A. Dittmann, Samuel N. Quinn, Akshata Krishnamurthy, Eric B. Ting

Comments: Published in The Astronomical Journal, 159, 60. 21 pages, 11 figures, 2 tables. This is the authors' version of the manuscript

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

[71]  arXiv:1905.05764 (replaced) [pdf, other]

Title: An Inflationary Probe of Cosmic Higgs Switching

Authors: JiJi Fan, Matthew Reece, Yi Wang

Comments: 28 pages, 9 figures. v2: improved analytic approximation and other minor changes; published in JHEP

Journal-ref: JHEP 05 (2020) 042

Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

[72]  arXiv:1907.12808 (replaced) [pdf, other]

Title: A 96 GeV scalar tagged to dark matter models

Authors: Anirban Kundu, Suvam Maharana, Poulami Mondal

Comments: 23 pages, 25 figures. v2: significant changes, with a proper treatment of the diphoton signal. Version to be published in Nuclear Physics B

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[73]  arXiv:1908.04823 (replaced) [pdf, ps, other]

Title: Early black-hole seeds in the first billion years

Authors: Umberto Maio

Comments: minor revisions and missing references added

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

[74]  arXiv:1909.00095 (replaced) [pdf, other]

Title: Significance of Gravitational Nonlinearities on the Dynamics of Disk Galaxies

Authors: Alexandre Deur, Corey Sargent, Balša Terzić

Comments: Accepted for publication in the Astrophysical Journal

Subjects: Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

[75]  arXiv:1910.03598 (replaced) [pdf, other]

Title: Forward Modeling of Double Neutron Stars: Insights from Highly-Offset Short Gamma-Ray Bursts

Authors: Michael Zevin, Luke Zoltan Kelley, Anya Nugent, Wen-fai Fong, Christopher P. L. Berry, Vicky Kalogera

Comments: 16 pages, 7 figures, 1 table. Submitted to AAS Journals. Changed fiducial population model to solar metallicity

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

[76]  arXiv:1911.12424 (replaced) [pdf, other]

Title: Escapees from the bar resonances. On the presence of low-eccentricity, metal-rich stars at the Solar vicinity

Authors: S. Khoperskov, P. Di Matteo, M. Haywood, A. Gomez, O. N. Snaith

Comments: 9 pages, 8 figures, A&A in press

Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

[77]  arXiv:1912.04872 (replaced) [pdf, other]

Title: Amending the halo model to satisfy cosmological conservation laws

Authors: Alice Y. Chen (Waterloo/Perimeter), Niayesh Afshordi (Waterloo/Perimeter)

Comments: Changes made to Figures 1-5 and Tables II-IV

Journal-ref: Phys. Rev. D. Volume 101 Issue 10, 103522 (2020)

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[78]  arXiv:2001.00085 (replaced) [pdf, other]

Title: How surfaces shape the climate of habitable exoplanets

Authors: Jack Madden, Lisa Kaltenegger

Comments: Published in MNRAS 11 February 2020 - 12 pages, 10 figures

Journal-ref: MNRAS, Volume 495, Issue 1, June 2020, Pages 1:11

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

[79]  arXiv:2001.00431 (replaced) [pdf, other]

Title: Wolf-Rayet galaxies in SDSS-IV MaNGA. I. Catalog construction and sample properties

Authors: Fu-Heng Liang (1), Cheng Li (1), Niu Li (1), Renbin Yan (2), Houjun Mo (1 and 3), Wei Zhang (4), Camilo Machuca (5), Alexandre Roman-Lopes (6) ((1) Tsinghua Univ., (2) Univ. of Kentucky, (3) Univ. of Massachusetts Amherst, (4) NAOC, (5) Univ. of Wisconsin Madison, (6) Univ. de La Serena)

Comments: 20 pages, 12 figures, 2 tables; Accepted for publication in ApJ

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[80]  arXiv:2001.00950 (replaced) [pdf, other]

Title: Ready, set, launch: time interval between BNS merger and short GRB jet formation

Authors: Paz Beniamini, Rodolfo Barniol Duran, Maria Petropoulou, Dimitrios Giannios

Comments: 15 pages, 8 figures. Accepted for publication in ApJ Letters

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

[81]  arXiv:2001.11105 (replaced) [pdf, other]

Title: Exploring the dispersion measure of the Milky Way halo

Authors: Laura C. Keating, Ue-Li Pen

Comments: 5 pages, 4 figures. Accepted to MNRAS Letters

Subjects: Astrophysics of Galaxies (astro-ph.GA)

[82]  arXiv:2002.09503 (replaced) [pdf, other]

Title: Multiple Chemodynamic Stellar Populations of the Ursa Minor Dwarf Spheroidal Galaxy

Authors: Andrew B. Pace (CMU), Manoj Kaplinghat (UCI), Evan Kirby (Caltech), Joshua D. Simon (Carnegie Obs), Erik Tollerud (STSci), Ricardo R. Muñoz (U. Chile), Patrick Côté (NRC), S. G. Djorgovski (Caltech), Marla Geha (Yale)

Comments: 20 pages, 11 figures, data included. Comments welcome. Accepted to MNRAS

Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

[83]  arXiv:2002.10575 (replaced) [pdf, other]

Title: Oscillation of high-energy neutrinos from choked jets in stellar and merger ejecta

Authors: Jose Carpio, Kohta Murase

Comments: 11 pages

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

[84]  arXiv:2003.08014 (replaced) [pdf, other]

Title: Numerical solutions to Einstein's equations in a shearing-dust Universe: a code comparison

Authors: Julian Adamek, Cristian Barrera-Hinojosa, Marco Bruni, Baojiu Li, Hayley J. Macpherson, James B. Mertens

Comments: 14 pages, 5 figures, accepted to CQG

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

[85]  arXiv:2003.13580 (replaced) [pdf, other]

Title: Two-moment scheme for general-relativistic radiation hydrodynamics: a systematic description and new applications

Authors: Lukas R. Weih, Hector Olivares, Luciano Rezzolla

Comments: 22 pages, 15 figures, matches version accepted to MNRAS

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

[86]  arXiv:2003.14371 (replaced) [pdf, other]

Title: Allesfitter: Flexible Star and Exoplanet Inference From Photometry and Radial Velocity

Authors: Maximilian N. Günther, Tansu Daylan

Comments: 36 pages, 15 figures, 9 tables, submitted to AAS journals

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

[87]  arXiv:2004.13280 (replaced) [pdf]

Title: A facility for mass production of ultra-pure NaI powder for the COSINE-200 experiment

Authors: Keonah Shin, Junseok Choe, Olga Gileva, Alain Iltis, Yeongduk Kim, Cheolho Lee, Hyun Su Lee, Moo Hyun Lee, Hyang Kyu Park

Comments: Proceeding for INSTR20, accepted in JINST

Subjects: Instrumentation and Detectors (physics.ins-det); Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Physics - Experiment (hep-ex); Nuclear Experiment (nucl-ex)

[88]  arXiv:2004.13811 (replaced) [pdf, other]

Title: Localizing merging black holes with sub-arcsecond precision using gravitational-wave lensing

Authors: Otto A. Hannuksela, Thomas E. Collett, Mesut Çalışkan, Tjonnie G. F. Li

Comments: 5 pages (main text) + 5 pages (methods+references), 5 figures, revisions to formatting

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

[89]  arXiv:2005.00177 (replaced) [pdf, other]

Title: Extrapolation of Three Dimensional Magnetic Field Structure in Flare-Productive Active Regions with Different Initial Conditions

Authors: Y. Kawabata, S. Inoue, T. Shimizu

Comments: accepted in ApJ

Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

[90]  arXiv:2005.00553 (replaced) [pdf, other]

Title: Simulations of stellar winds from X-ray bursts. Characterization of solutions and observable variables

Authors: Yago Herrera, Gloria Sala, Jordi José

Comments: Accepted in Astronomy and Astrophysics. New version with corrected typo in eq. (36) and some minor changes after language edition

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE)

[91]  arXiv:2005.04336 (replaced) [pdf, other]

Title: Optical and X-ray observations of stellar flares on an active M dwarf AD Leonis with Seimei Telescope, SCAT, NICER and OISTER

Authors: Kosuke Namekata, Hiroyuki Maehara, Ryo Sasaki, Hiroki Kawai, Yuta Notsu, Adam F. Kowalski, Joel C. Allred, Wataru Iwakiri, Yohko Tsuboi, Katsuhiro L. Murata, Masafumi Niwano, Kazuki Shiraishi, Ryo Adachi, Kota Iida, Motoki Oeda, Satoshi Honda, Miyako Tozuka, Noriyuki Katoh, Hiroki Onozato, Soshi Okamoto, Keisuke Isogai, Mariko Kimura, Naoto Kojiguchi, Yasuyuki Wakamatsu, Yusuke Tampo, Daisaku Nogami, Kazunari Shibata

Comments: 18 pages, 17 figures, Accepted for Publication in PASJ

Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); High Energy Astrophysical Phenomena (astro-ph.HE)

[92]  arXiv:2005.06505 (replaced) [pdf]

Title: PypeIt: The Python Spectroscopic Data Reduction Pipeline

Authors: J. Xavier Prochaska (1, 2), Joseph F. Hennawi (3), Kyle B. Westfall (4), Ryan J. Cooke (5), Feige Wang (3,6), Tiffany Hsyu (1), Frederick B. Davies (3,7), Emanuele Paolo Farina (3,8) ((1) University of California, Santa Cruz, (2) Kavli Institute for the Physics and Mathematics of the Universe, (3) University of California, Santa Barbara, (4) University of California Observatories, (5) Durham University, UK, (6) Steward Observatory, University of Arizona, (7) Lawrence Berkeley National Laboratory, (8) Max Planck Institut fur Astrophysik)

Comments: To be submitted to JOSS (once they return to accepting submissions). Find PypeIt at: this https URL

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

[93]  arXiv:2005.08815 (replaced) [pdf, other]

Title: A Detailed Examination of Anisotropy and Timescales in Three-dimensional Incompressible Magnetohydrodynamic Turbulence

Authors: Rohit Chhiber, William H. Matthaeus, Sean Oughton, Tulasi N. Parashar

Comments: In Press at Physics of Plasmas

Subjects: Plasma Physics (physics.plasm-ph); Solar and Stellar Astrophysics (astro-ph.SR); Computational Physics (physics.comp-ph); Fluid Dynamics (physics.flu-dyn); Space Physics (physics.space-ph)

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