We gratefully acknowledge support from
the Simons Foundation and Leiden University.

Astrophysics

New submissions

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New submissions for Mon, 9 Dec 19

[1]  arXiv:1912.02821 [pdf, other]
Title: XO-7 b: A transiting hot Jupiter with a massive companion on a wide orbit
Comments: 16 pages, 6 figures, Accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

Transiting planets orbiting bright stars are the most favorable targets for follow-up and characterization. We report the discovery of the transiting hot Jupiter XO-7 b and of a second, massive companion on a wide orbit around a circumpolar, bright, and metal rich G0 dwarf (V = 10.52, $T_{\rm eff} = 6250 \pm 100 \; \rm K$, $\rm[Fe/H] = 0.432 \pm 0.057 \; \rm dex$). We conducted photometric and radial velocity follow-up with a team of amateur and professional astronomers. XO-7 b has a period of $ 2.8641424 \pm 0.0000043$ days, a mass of $0.709 \pm 0.034 \; \rm M_{\rm J}$, a radius of $1.373 \pm 0.026 \; \rm R_{\rm J}$, a density of $0.340 \pm 0.027 \; \rm g \, {cm}^{-3}$, and an equilibrium temperature of $1743 \pm 23 \; \rm K$. Its large atmospheric scale height and the brightness of the host star make it well suited to atmospheric characterization. The wide orbit companion is detected as a linear trend in radial velocities with an amplitude of $\sim100 \; \rm m \, {s}^{-1}$ over two years, yielding a minimum mass of $4 \; \rm M_{\rm J}$; it could be a planet, a brown dwarf, or a low mass star. The hot Jupiter orbital parameters and the presence of the wide orbit companion point towards a high eccentricity migration for the hot Jupiter. Overall, this system will be valuable to understand the atmospheric properties and migration mechanisms of hot Jupiters and will help constrain the formation and evolution models of gas giant exoplanets.

[2]  arXiv:1912.02823 [pdf, other]
Title: A CMB Millikan Experiment with Cosmic Axiverse Strings
Comments: 35 pages, 10 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

We study axion strings of hyperlight axions coupled to photons. Hyperlight axions -- axions lighter than Hubble at recombination -- are a generic prediction of the string axiverse. These axions strings produce a distinct quantized polarization rotation of CMB photons which is $\mathcal{O}(\alpha_{\rm em})$. As the CMB light passes many strings, this polarization rotation converts E-modes to B-modes and adds up like a random walk. Using numerical simulations we show that the expected size of the final result is well within the reach of current and future CMB experiments through the measurement of correlations of CMB B-modes with E- and T-modes. The quantized polarization rotation angle is topological in nature and can be seen as a geometric phase. Its value depends only on the anomaly coefficient and is independent of other details such as the axion decay constant. Measurement of the anomaly coefficient by measuring this rotation will provide information about the UV theory, such as the quantization of electric charge and the value of the fundamental unit of charge. The presence of axion strings in the universe relies only on a phase transition in the early universe after inflation, after which the string network rapidly approaches an attractor scaling solution. If there are additional stable topological objects such as domain walls, axions as heavy as $10^{-15}$ eV would be accessible. The existence of these strings could also be probed by measuring the relative polarization rotation angle between different images in gravitationally lensed quasar systems.

[3]  arXiv:1912.02824 [pdf, ps, other]
Title: No significant evolution of relations between Black hole mass and Galaxy total stellar mass up to z~2.5
Comments: 16 pages, 7 figures, accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We investigate the cosmic evolution of the ratio between black hole mass (MBH) and host galaxy total stellar mass (Mstellar) out to z~2.5 for a sample of 100 X-ray-selected moderate-luminosity, broad-line active galactic nuclei (AGNs) in the Chandra-COSMOS Legacy Survey. By taking advantage of the deep multi-wavelength photometry and spectroscopy in the COSMOS field, we measure in a uniform way the galaxy total stellar mass using a SED decomposition technique and the black hole mass based on broad emission line measurements and single-epoch virial estimates. Our sample of AGN host galaxies has total stellar masses of 10^10-12Msun, and black hole masses of 10^7.0-9.5Msun. Combining our sample with the relatively bright AGN samples from the literature, we find no significant evolution of the MBH-Mstellar relation with black hole-to-host total stellar mass ratio of MBH/Mstellar~0.3% at all redshifts probed. We conclude that the average black hole-to-host stellar mass ratio appears to be consistent with the local value within the uncertainties, suggesting a lack of evolution of the MBH-Mstellar relation up to z~2.5.

[4]  arXiv:1912.02825 [pdf, other]
Title: Simulating dust grain-radiation coupling on a moving mesh
Authors: Ryan McKinnon (MIT), Rahul Kannan (Harvard), Mark Vogelsberger (MIT), Stephanie O'Neil (MIT), Paul Torrey (UFL), Hui Li (MIT)
Comments: 11 pages, 6 figures, submitted to MNRAS, comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We present a model for the interaction between dust and radiation fields in the radiation hydrodynamic code AREPO-RT, which solves the moment-based radiative transfer equations on an unstructured moving mesh. Dust is directly treated using live simulation particles, each of which represent a population of grains that are coupled to hydrodynamic motion through a drag force. We introduce methods to calculate radiation pressure on and photon absorption by dust grains. By including a direct treatment of dust, we are able to calculate dust opacities and update radiation fields self-consistently based on the local dust distribution. This hybrid scheme coupling dust particles to an unstructured mesh for radiation is validated using several test problems with known analytic solutions, including dust driven via spherically-symmetric flux from a constant luminosity source and photon absorption from radiation incident on a thin layer of dust. Our methods are compatible with the multifrequency scheme in AREPO-RT, which treats UV and optical photons as single-scattered and IR photons as multi-scattered. At IR wavelengths, we model heating of and thermal emission from dust. Dust and gas are not assumed to be in local thermodynamic equilibrium but transfer energy through collisional exchange. We estimate dust temperatures by balancing these dust-radiation and dust-gas energy exchange rates. This framework for coupling dust and radiation can be applied in future radiation hydrodynamic simulations of galaxy formation.

[5]  arXiv:1912.02827 [pdf, other]
Title: XXL Survey groups and clusters in the Hyper Suprime-Cam Survey. Scaling relations between X-ray properties and weak lensing mass
Comments: 19 pages; in press on MNRAS. One of two companion papers on HSC-XXL surveys (Keiichi Umetsu et al., arXiv:1909.10524)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Scaling relations trace the formation and evolution of galaxy clusters. We exploited multi-wavelength surveys -- the XXL survey at \emph{XMM-Newton} in the X-ray band, and the Hyper Suprime-Cam Subaru Strategic Program for optical weak lensing -- to study an X-ray selected, complete sample of clusters and groups. The scalings of gas mass, temperature, and soft-band X-ray luminosity with the weak lensing mass show imprints of radiative cooling and AGN feedback in groups. From the multi-variate analysis, we found some evidence for steeper than self-similar slopes for gas mass ($\beta_{m_\text{g}|m}=1.73 \pm0.80$) and luminosity ($\beta_{l|m}=1.91\pm0.94$) and a nearly self-similar slope for the temperature ($\beta_{t|m}=0.78\pm0.43$). Intrinsic scatters of X-ray properties appear to be positively correlated at a fixed mass (median correlation factor $\rho_{X_1X_2|m}\sim0.34$) due to dynamical state and merger history of the halos. Positive correlations with the weak lensing mass (median correlation factor $\rho_{m_\text{wl}X|m}\sim0.35$) can be connected to triaxiality and orientation. Comparison of weak lensing and hydrostatic masses suggests a small role played by non-thermal pressure support ($9\pm17\%$).

[6]  arXiv:1912.02829 [pdf, other]
Title: BreakBRD Galaxies I: Global Properties of Spiral Galaxies with Central Star Formation in Red Disks
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We introduce a collection of primarily centrally star-forming galaxies that are selected by disk color to have truncated disk star formation. We show that common explanations for centrally-concentrated star formation -- low stellar mass, bars, and high-density environments, do not universally apply to this sample. To gain insight into our sample, we compare these galaxies to a parent sample of strongly star-forming galaxies and to a parent sample of galaxies with low specific star formation rates. We find that in star formation and color space from ultraviolet to the infrared these galaxies either fall between the two samples or agree more closely with galaxies with high-specific star formation rates. Their morphological characteristics also lie between high- and low-specific star formation rate galaxies, although their Petrosian radii agree well with that of the low-specific star formation rate parent sample. We discuss whether this sample is likely to be quenching or showing an unusual star-formation distribution while continuing to grow through star formation. Future detailed studies of these galaxies will give us insights into how the local conditions within a galaxy balance environmental influence to govern the distribution of star formation. In this first paper in a series, we describe the global properties that identify this sample as separate from more average spiral galaxies, and identify paths forward to explore the underlying causes of their differences.

[7]  arXiv:1912.02831 [pdf, other]
Title: Galaxy sizes and the galaxy-halo connection -- I: the remarkable tightness of the size distributions
Comments: 22 pages, 14 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The mass and structural assembly of galaxies is a matter of intense debate. Current theoretical models predict the existence of a linear relationship between galaxy size ($R_e$) and the host dark matter halo virial radius ($R_h$).\\ By making use of semi-empirical models compared to the size distributions of central galaxies from the Sloan Digital Sky Survey, we provide robust constraints on the normalization and scatter of the $R_e-R_h$ relation. We explore the parameter space of models in which the $R_e-R_h$ relation is mediated by either the spin parameter or the concentration of the host halo, or a simple constant the nature of which is in principle unknown. We find that the data require extremely tight relations for both early-type and late-type galaxies (ETGs,LTGs), especially for more massive galaxies. These constraints challenge models based solely on angular momentum conservation, which predict significantly wider distributions of galaxy sizes and no trend with stellar mass, if taken at face value. We discuss physically-motivated alterations to the original models that bring the predictions into better agreement with the data. We argue that the measured tight size distributions of SDSS disk galaxies can be reproduced by semi-empirical models in which the $R_e-R_h$ connection is mediated by the \emph{stellar} specific angular momenta $j_{star}.$ We find that current cosmological models of galaxy formation broadly agree with our constraints for LTGs, and justify the strong link between $R_e$ and $j_{star}$ that we propose, however the tightness of the $R_e-R_h$ relation found in such ab-initio theoretical models for ETGs is in tension with our semi-empirical findings.

[8]  arXiv:1912.02833 [pdf, other]
Title: A record of the final phase of giant planet migration fossilized in the asteroid belt's orbital structure
Comments: 5 pages, 4 figures, 2 tables, accepted for publication in MRNAS Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The asteroid belt is characterized by an extreme low total mass of material on dynamically excited orbits. The Nice Model explains many peculiar qualities of the solar system, including the belt's excited state, by invoking an orbital instability between the outer planets. However, previous studies of the Nice Model's effect on the belt's structure struggle to reproduce the innermost asteroids' orbital inclination distribution. Here, we show how the final phase of giant planet migration sculpts the asteroid belt, in particular its inclination distribution. As interactions with leftover planetesimals cause Saturn to move away from Jupiter, its rate of orbital precession slows as the two planets' mutual interactions weaken. When the planets approach their modern separation, where Jupiter completes just short of five orbits for every two of Saturn's, Jupiter's eccentric forcing on Saturn strengthens. We use numerical simulations to show that the absence of asteroids with orbits that precess between 24-28 arcsec/yr is related to the inclination problem. As Saturn's precession speeds back up, high inclination asteroids are excited on to planet crossing orbits and removed from the inner main belt. Through this process, the asteroid belt's orbital structure is reshaped, leading to markedly improved simulation outcomes.

[9]  arXiv:1912.02834 [pdf, other]
Title: Models of Bars with Exponential Density Profiles
Authors: D. P. McGough, N. W. Evans, J. L. Sanders (IoA, Cambridge)
Comments: MNRAS, submitted
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a new model for galactic bars with exponentially falling major axis luminosity profiles and Gaussian cross-sections. This is based on the linear superposition of Gaussian potential-density pairs with an exponential weight function, using an extension of the method originally introduced by Long & Murali (1992). We compute the density, potential and forces, using Gaussian quadrature. These quantities are given as explicit functions of position. There are three independent scaled bar parameters that can be varied continuously to produce bespoke bars of a given mass and shape. We categorise the effective potential by splitting a reduced parameter space into six regions. Unusually, we find bars with three stable Lagrange points on the major axis are possible. Our model reveals a variety of unexpected orbital structure, including a bifurcating $x_1$ orbit coexisting with a stable $x_4$ orbit. Propeller orbits are found to play a dominant role in the orbital structure, and we find striking similarities between our bar configuration and the model of Kaufmann & Contopoulos (1996). We find a candidate orbital family, sired from the propeller orbits, that may be responsible for the observed high velocity peaks in the Milky Way's bar. As a cross-check, we inspect, for the first time, the proper motions of stars in the high velocity peaks, which also match our suggested orbital family well. This work adds to the increasing body of evidence that real galactic bars may be supported at least partly by propeller orbits rather than solely the $x_1$ family.

[10]  arXiv:1912.02837 [pdf, ps, other]
Title: The BAT AGN Spectroscopic Survey -- XVIII. Searching for Supermassive Black Hole Binaries in the X-rays
Comments: 14 pages. Resubmitted to ApJ after first round of referee comments
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Theory predicts that a supermassive black hole binary (SMBHB) could be observed as a luminous active galactic nucleus (AGN) that periodically varies on the order of its orbital timescale. In X-rays, periodic variations could be caused by mechanisms including relativistic Doppler boosting and shocks. Here we present the first systematic search for periodic AGNs using 941 hard X-ray light curves (14-195 keV) from the first 105 months of the Swift Burst Alert Telescope (BAT) survey (2004-2013). While we do not find evidence for periodic AGNs in Swift-BAT, we have investigated the detectability of SMBHBs in the context of the eROSITA survey by adopting prescriptions for AGN X-ray variability and the periodic variability from a population of SMBHBs and assuming weekly and monthly temporal sampling rates. Even under generous assumptions about the binary population in AGNs, the detectable fraction is modest due to the challenge of distinguishing the periodic signal from normal AGN variability. Due to this effect of "red noise", we instead find that the search for SMBHBs would greatly benefit from sampling a large number of AGNs at lower cadence.

[11]  arXiv:1912.02843 [pdf, other]
Title: Estimation of the jet inclination angle for the TDE Swift J1644+57
Authors: Sudip Chakraborty (Tata Institute of Fundamental Research, India), Sudip Bhattacharyya (Tata Institute of Fundamental Research, India), Chandrachur Chakraborty (Kavli Institute for Astronomy and Astrophysics, Peking University, China), A. R. Rao (Tata Institute of Fundamental Research, India)
Comments: 7 pages, 4 figures, accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

An estimate of the jet inclination angle relative to the accreting black hole's spin can be useful to probe the jet triggering mechanism and the disc--jet coupling. A Tidal Disruption Event (TDE) of a star by a supermassive spinning black hole provides an excellent astrophysical laboratory to study the jet direction through the possibility of jet precession. In this work, we report a new method to constrain the jet inclination angle $\beta$ and apply it to the well-sampled jetted TDE Swift J1644+57. This method involves X-ray data analysis and comparisons of jet models with broad properties of the observed X-ray dips, to estimate the upper limit of the extent of the contribution of a plausible jet precession to these X-ray dips. From this limit, we find that $\beta$ is very likely to be less than $\sim 15^\circ$ for Swift J1644+57. Such a well-constrained jet inclination angle could be useful to probe the jet physics. The main advantage of our method is that it does not need to assume an origin of the observed X-ray dips, and the conclusion does not depend on any particular type of jet precession (e.g., the one due to the Lense-Thirring effect) or any specific value of precession frequency or any particular jet model. These make this method reliable and applicable to other jetted TDEs, as well as to other jetted accreting systems.

[12]  arXiv:1912.02847 [pdf, other]
Title: The MUSE view of the planetary nebula NGC 3132
Authors: Ana Monreal-Ibero (1,2), Jeremy R. Walsh (3) ((1) Instituto de Astrofísica de Canarias, (2) Universidad de La Laguna, (3) European Southern Observatory)
Comments: 21 pages, 15 figures, 6 tables; accepted by A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

ABRIDGED: 2D spectroscopic MUSE data for the whole extent of NGC3132 have been reduced and analised. The dust extinction, electron densities and temperatures of the ionised gas and abundances were determined. The nebula presents a complex reddening structure with high values (c(Hb)~0.4) at the rim. Density maps are compatible with an inner high-ionisation plasma at moderate high density (~1000cm^-3) while the low-ionisation plasma presents a structure in density peaking at the rim with values ~700 cm^-3. Median Te using different diagnostics decreases according to the sequence [NII],[SII]->[SIII]->[OI]->HeI->PJ. Likewise the range of Te covered by recombination lines is much larger than those obtained from CELs, with large spatial variations within the nebula. If these differences were due to the existence of high density clumps, these spatial variations suggest changes in the properties and/or distribution of the clumps within the nebula. We determined a median He/H=0.124. The range of measured ionic abundances for light elements are compatible with literature values. Our kinematic analysis nicely illustrates the power of 2D kinematic information in many emission lines to shed light on the intrinsic structure of the nebula. Our derived velocity maps support a geometry for the nebula similar to the previously propose diabolo model, but oriented with its major axis at P.A.~-22^o. We identified two low-surface brightness arc-like structures towards the northern and southern tips of the nebula, with high extinction, high helium abundance, and strong low-ionisation emission lines. They are spatially coincident with some extended low-surface brightness mid-IR emission. The characteristics of the features are compatible with being the consequence of precessing jets caused by the binary star system. This study illustrates the enormous potential of IFS for the study of Galactic PNe.

[13]  arXiv:1912.02849 [pdf, ps, other]
Title: Crystallization of the outer crust of a non-accreting neutron star
Comments: 15 pages, 8 figures, accepted for publication in Astronomy and Astrophysics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)

The interior of a neutron star (NS) is usually assumed to be made of cold catalyzed matter. However, the outer layers are unlikely to remain in full equilibrium during the formation of the star and its cooling, especially after crystallization. We study the cooling and equilibrium composition of the outer layers of a NS down to crystallization. Here the impurity parameter, usually a free parameter in cooling simulations, is calculated self-consistently using a microscopic model for which a unified equation of state has recently been determined. We follow the evolution of the nuclear distributions of the multi-component Coulomb liquid plasma (MCP) fully self-consistently, adapting a general formalism originally developed for the description of supernova cores. We calculate the impurity parameter at the crystallization as determined in the one-component plasma (OCP) approximation. Our analysis shows that the sharp changes in composition obtained in the OCP approximation are smoothed out when a full nuclear distribution is allowed. The Coulomb coupling parameter at melting is found to be reasonably close to the canonical value of 175, except for specific pressures for which supercooling occurs in the OCP approximation. Our MCP treatment leads to non-monotonic variations of the impurity parameter with pressure. Its values can change by several orders of magnitude reaching about 50, suggesting that the crust may be composed of an alternation of pure (highly conductive) and impure (highly resistive) layers. The results presented here complement the recent unified equation of state obtained with the same model. Our self-consistent approach to hot MCP shows that the presence of impurities in the outer crust of a NS is non-negligible and may have a sizeable impact on transport properties. In turn, this may have important implications for the cooling of NS and their magneto-rotational evolution.

[14]  arXiv:1912.02855 [pdf, other]
Title: Surveying the Giant HII Regions of the Milky Way with SOFIA: II. M17
Comments: 25 pages, 16 figures, 9 tables, accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We present our second set of results from our mid-infrared imaging survey of Milky Way Giant HII regions. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy to obtain 20 and 37$\mu$m images of the central ~10'X10' area of M17. We investigate the small- and large-scale properties of M17 using our data in conjunction with previous multi-wavelength observations. The spectral energy distributions of individual compact sources were constructed with Spitzer-IRAC, SOFIA-FORCAST, and Herschel-PACS photometry data and fitted with massive young stellar object (MYSO) models. Seven sources were found to match the criteria for being MYSO candidates, four of which are identified here for the first time, and the stellar mass of the most massive object, UC1, is determined to be 64 solar mass. We resolve the extended mid-infrared emission from the KW Object, and suggest that the angle of this extended emission is influenced by outflow. IRS5 is shown to decrease in brightness as a function of wavelength from the mid- to far-infrared, and has several other indicators that point to it being an intermediate mass Class II object and not a MYSO. We find that the large-scale appearance of emission in M17 at 20$\mu$m is significantly affected by contamination from the [SIII] emission line from the ionized gas of the Giant HII region. Finally, a number of potential evolutionary tracers yield a consistent picture suggesting that the southern bar of M17 is likely younger than the northern bar.

[15]  arXiv:1912.02856 [pdf, other]
Title: Switchbacks in the near-Sun magnetic field: long memory and impact on the turbulence cascade
Comments: 10 figures, to appear in The Astrophysical Journal Supplement Series (2020)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

One of the most striking observations made by Parker Solar Probe during its first solar encounter is the omnipresence of rapid polarity reversals in a magnetic field that is otherwise mostly radial. These so-called switchbacks strongly affect the dynamics of the magnetic field. We concentrate here on their macroscopic properties. First, we find that these structures are self-similar, and have neither a characteristic magnitude, nor a characteristic duration. Their waiting time statistics shows evidence for aggregation. The associated long memory resides in their occurrence rate, and is not inherent to the background fluctuations. Interestingly, the spectral properties of inertial range turbulence differ inside and outside of switchback structures; in the latter the $1/f$ range extends to higher frequencies. These results suggest that outside of these structures we are in the presence of lower amplitude fluctuations with a shorter turbulent inertial range. We conjecture that these correspond to a pristine solar wind.

[16]  arXiv:1912.02860 [pdf, other]
Title: Introducing the Search for Intermediate-mass Black-hole In Nearby Galaxy (SIBLING) Survey
Authors: Jorge Martínez-Palomera (1), Paulina Lira (2), India Bhalla-Ladd (3), Francisco Förster (4), Richard M. Plotkin (5) ((1) Department of Astronomy, University of California, Berkeley, USA, (2) Department of Astronomy, University of Chile, Chile, (3) Department of Physics, Yale University, USA, (4) Center for Mathematical Modeling, University of Chile, Chile, (5) Department of Physics, University of Nevada, Reno, USA)
Comments: 16 pages (including Appendix), 15 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Intermediate mass black holes (IMBHs) have masses between the $10^2\!-\!10^6$ M$_\odot$ and are key to our understanding of the formation of massive black holes. The known population of IMBH remains small, with a few hundred candidates and only a handful of them confirmed as bona-fide IMBHs. Until now, the most widely used selection method is based on spectral analysis. Here we present a methodology to select IMBH candidates via optical variability analysis of the nuclear region of local galaxies ($z \leqslant 0.35$). Active IMBH accreting at low rates show small amplitude variability with time scales of hours, as it is seen in one of the known IMBH NGC4395. We found a sample of $\sim \!500$ galaxies evidencing fast and small amplitude variation in their weekly based light curves. We estimate an average occupancy fraction of 4\% and a surface density of $\sim \!3$ deg$^{-2}$, which represent an increase by a factor of $\sim\!40$ compared to previous searches. A large fraction ($78\%$) of the candidates are in spiral galaxies. We preliminary confirm the AGN nature of 22 sources via BPT diagrams using SDSS legacy spectra. Further confirmation of these candidates will require multiwavelength observations, especially in X-ray and radio bands.

[17]  arXiv:1912.02862 [pdf, other]
Title: Habitable Age Instead of Location for Terrestrial Worlds
Comments: 7 pages; 4 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The presence of a liquid solvent is widely regarded as an essential prerequisite for habitability. We investigate the conditions under which worlds outside the habitable zones of stars are capable of supporting liquid solvents on their surface over geologically significant timescales via combined radiogenic and primordial heat. Our analysis suggests that super-Earths with radionuclide abundances that are $\gtrsim 10^3$ times higher than Earth can host long-lived water oceans. In contrast, the requirements for long-lived ethane oceans, which have been explored in the context of alternative biochemistries, are less restrictive: relative radionuclide abundances of $\gtrsim 10^2$ could be sufficient. At such radionuclide levels, we find that these worlds may be detectable ($10\sigma$ detection over $\sim 10$ days integration time at $12.8$ $\mu$m) by the James Webb Space Telescope at distances of $\sim 10$ pc if their ages are $\lesssim 1$ Gyr.

[18]  arXiv:1912.02888 [pdf, other]
Title: Seed Population Pre-Conditioning and Acceleration Observed by Parker Solar Probe
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

A series of solar energetic particle (SEP) events were observed at Parker Solar Probe (PSP) by the Integrated Science Investigation of the Sun (\ISOIS) during the period from April 18, 2019 through April 24, 2019. The PSP spacecraft was located near 0.48 au from the Sun on Parker spiral field lines that projected out to 1 au within $\sim 25^\circ$ of near Earth spacecraft. These SEP events, though small compared to historically large SEP events, were amongst the largest observed thus far in the PSP mission and provide critical information about the space environment inside 1 au during SEP events. During this period the Sun released multiple coronal mass ejections (CMEs). One of these CMEs observed was initiated on April 20, 2019 at 01:25 UTC, and the interplanetary CME (ICME) propagated out and passed over the PSP spacecraft. Observations by the Electromagnetic Fields Investigation (FIELDS) show that the magnetic field structure was mostly radial throughout the passage of the compression region and the plasma that followed, indicating that PSP did not directly observe a flux rope internal to the ICME, consistent with the location of PSP on the ICME flank. Analysis using relativistic electrons observed near Earth by the Electron, Proton and Alpha Monitor (EPAM) on the Advanced Composition Explorer (ACE) demonstrates the presence of electron seed populations (40--300 keV) during the events observed. The energy spectrum of the \ISOIS~ observed proton seed population below 1 MeV is close to the limit of possible stationary state plasma distributions out of equilibrium. \ISOIS~ observations reveal the \revise{enhancement} of seed populations during the passage of the ICME, which \revise{likely indicates a key part} of the pre-acceleration process that occurs close to the Sun.

[19]  arXiv:1912.02902 [pdf, other]
Title: Characterization of aliased noise in the Advanced ACTPol receiver
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Advanced ACTPol is the second generation polarization-sensitive upgrade to the $6\, \rm m$ aperture Atacama Cosmology Telescope (ACT), which increased detector count and frequency coverage compared to the previous ACTPol receiver. Advanced ACTPol utilizes a new two-stage time-division multiplexing readout architecture based on superconducting quantum interference devices (SQUIDs) to achieve a multiplexing factor as high as 64 (rows), fielding a 2,012 detector camera at 150/220 GHz and two 90/150 GHz cameras containing 1,716 detectors each. In a time domain system, aliasing introduces noise to the readout. In this work we present a figure of merit to measure this noise contribution and present measurements of the aliased noise fraction of the Advanced ACTPol receiver as deployed.

[20]  arXiv:1912.02904 [pdf, ps, other]
Title: The photon time delay in magnetized vacuum magnetosphere
Comments: 10 pages, 6 figures, and one appendix
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)

We study the transverse propagation of photons in a magnetized vacuum considering radiative corrections in the one-loop approximation. The dispersion equation is modified due to the magnetized photon self-energy in the transparency region ($0<\omega<2m_e$). The aim of our study is to explore the propagation of photons in a neutron star magnetosphere (described by magnetized vacuum). The solution of the dispersion equation is obtained in terms of analytic functions. The larger the magnetic field, the higher the phase velocity and the more the dispersion curve deviates from the light-cone. For fixed values of the frequency, we study the dependence of photon time delay with the magnetic field strength, as well as with distance. For the latter, we adopt a magnetic dipole configuration and obtain that, contrary to the expectation, photons of higher energy experience a longer time delay. A discussion of potential causes of this behaviour is presented.

[21]  arXiv:1912.02905 [pdf, other]
Title: The Sixteenth Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
Comments: DR16 date: Monday Dec 9th 2019. This is the alphabetical order SDSS-IV collaboration data release paper. 21 pages, 6 figures, submitted to ApJS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM)

This paper documents the sixteenth data release (DR16) from the Sloan Digital Sky Surveys; the fourth and penultimate from the fourth phase (SDSS-IV). This will be the first release of data from the Southern Hemisphere Survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release to contain data (spectra) from the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes the last data from the Time Domain Spectroscopic Survey (TDSS) and new data from the SPectroscopic IDentification of ERosita Survey (SPIDERS) programs, both of which co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).

[22]  arXiv:1912.02916 [pdf, other]
Title: The ALMA Frontier Fields survey V: ALMA Stacking of Lyman-Break Galaxies in Abell 2744, Abell 370, Abell S1063, MACSJ0416.1-2403 and MACSJ1149.5+2223
Comments: Accepted for publication in A&A, 28 pages and 20 figures. Full versions of Tables C.1, C.2, C.3, C.4, and C.5 are available for download at this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The Hubble Frontier Fields offer an exceptionally deep window into the high-redshift universe, covering a substantially larger area than the Hubble Ultra-Deep field at low magnification and probing 1--2 mags deeper in exceptional high-magnification regions. We aim to leverage Atacama Large Millimetre Array (ALMA) band 6 ($\approx$263\,GHz) mosaics in the central portions of five Frontier Fields to characterize the infrared (IR) properties of $1582$ ultraviolet (UV)-selected Lyman-Break Galaxies (LBGs) at redshifts of $z {\sim}$2--8. We investigated individual and stacked fluxes and IR excess (IRX) values of the LBG sample as functions of stellar mass ($\mathrm{M}_{\bigstar}$), redshift, UV luminosity and slope $\beta$, and lensing magnification. Two (2) LBG candidates were individually detected above a significance of $4.1{-}\sigma$, while stacked samples of the remaining LBG candidates yielded no significant detections. We investigated our detections and upper limits in the context of the IRX-$\mathrm{M}_{\bigstar}$ and IRX-$\beta$ relations, probing at least one dex lower in stellar mass than past studies have done. Our upper limits exclude substantial portions of parameter space and they are sufficiently deep in a handful of cases to create mild tension with the typically assumed attenuation and consensus relations. We observe a clear and smooth trend between $\mathrm{M}_{\bigstar}$ and $\beta$, which extends to low masses and blue (low) $\beta$ values, consistent with expectations from previous works.

[23]  arXiv:1912.02934 [pdf, ps, other]
Title: Surveying the reach and maturity of machine learning and artificial intelligence in astronomy
Comments: 40 pages, accepted for publication in WIREs Data Mining and Knowledge Discovery (9 November 2019)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Machine learning (automated processes that learn by example in order to classify, predict, discover or generate new data) and artificial intelligence (methods by which a computer makes decisions or discoveries that would usually require human intelligence) are now firmly established in astronomy. Every week, new applications of machine learning and artificial intelligence are added to a growing corpus of work. Random forests, support vector machines, and neural networks (artificial, deep, and convolutional) are now having a genuine impact for applications as diverse as discovering extrasolar planets, transient objects, quasars, and gravitationally-lensed systems, forecasting solar activity, and distinguishing between signals and instrumental effects in gravitational wave astronomy. This review surveys contemporary, published literature on machine learning and artificial intelligence in astronomy and astrophysics. Applications span seven main categories of activity: classification, regression, clustering, forecasting, generation, discovery, and the development of new scientific insight. These categories form the basis of a hierarchy of maturity, as the use of machine learning and artificial intelligence emerges, progresses or becomes established.

[24]  arXiv:1912.02935 [pdf, ps, other]
Title: Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model and Core Formation of FeSt 1-457
Comments: Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Observational data for the hourglass-like magnetic field toward the starless dense core FeSt 1-457 were compared with a flux freezing magnetic field model (Myers et al. 2018). Fitting of the observed plane-of-sky magnetic field using the flux freezing model gave a residual angle dispersion comparable with the results based on a simple three-dimensional parabolic model. The best-fit parameters for the flux freezing model were a line-of-sight magnetic inclination angle of $\gamma_{\rm mag} = 35^{\circ} \pm 15^{\circ}$ and a core center to ambient (background) density contrast of $\rho_{\rm c} / \rho_{\rm bkg} = 75$. The initial density for core formation ($\rho_0$) was estimated to be $\rho_{\rm c} / 75 = 4670$ cm$^{-3}$, which is about one order of magnitude higher than the expected density ($\sim 300$ cm$^{-3}$) for the inter-clump medium of the Pipe Nebula. FeSt 1-457 is likely to have been formed from the accumulation of relatively dense gas, and the relatively dense background column density of $A_V \simeq 5$ mag supports this scenario. The initial radius (core formation radius) $R_0$ and the initial magnetic field strength $B_0$ were obtained to be 0.15 pc ($1.64 R$) and $10.8-14.6$ $\mu$G, respectively. We found that the initial density $\rho_0$ is consistent with the mean density of the nearly critical magnetized filament with magnetic field strength $B_0$ and radius $R_0$. The relatively dense initial condition for core formation can be naturally understood if the origin of the core is the fragmentation of magnetized filaments.

[25]  arXiv:1912.02941 [pdf, other]
Title: Global Simulations of the Vertical Shear Instability with Non-ideal Magnetohydrodynamical Effects
Authors: Can Cui, Xue-Ning Bai
Comments: 18 pages, 15 figures, ApJ submitted
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The mechanisms of angular momentum transport and level of turbulence in protoplanetary disks (PPDs) are crucial for understanding many aspects of planet formation. In the recent years, it has been realized that the magneto-rotational instability (MRI) tends to be suppressed in PPDs due to non-ideal MHD effects, and the disk is largely laminar with accretion driven by magnetized disk winds. In parallel, several hydrodynamical mechanisms have been identified that likely also generate vigorous turbulence and drive disk accretion. We study the interplay between MHD winds in PPDs with the vertical shear instability (VSI), one of the most promising hydrodynamical mechanisms, through 2D global non-ideal MHD simulations with ambipolar diffusion and Ohmic resistivity. We find that for typical disk parameters, MHD winds can coexist with the VSI with accretion primarily wind-driven accompanied by vigorous VSI turbulence. The properties of the VSI remain similar to unmagnetized case, and the wind and overall field configuration are not strongly affected by VSI turbulence, showing modest level of variability and corrugation of midplane current sheet. Enhanced coupling between gas and magnetic field weakens the VSI. The VSI is also weakened with increasing magnetization, and we find that corrugation motions characteristic of the VSI transitions to low-amplitude breathing mode oscillations.

[26]  arXiv:1912.03068 [pdf, other]
Title: The Final SDSS-IV/SPIDERS X-ray Point Source Spectroscopic Catalogue
Comments: submitted to A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

SPIDERS (SPectroscopic IDentification of ERosita Sources) is a SDSS-IV program aimed at obtaining spectroscopic classification and redshift measurements for complete samples of sufficiently bright X-ray sources. We describe the SPIDERS X-ray Point Source Spectroscopic Catalog, which contains 11,092 observed spectra drawn from a parent sample of 14,759 ROSAT and XMM sources over an area of 5,129deg$^2$ covered in SDSS-IV by the eBOSS survey. This program represents the largest systematic spectroscopic observation of an X-ray selected sample. A total of 10,970 (98.9\%) of the observed objects are classified, and 10,849 (97.8\%) have secure redshifts. The majority of the spectra, 10,070 are AGN, 522 are cluster galaxies, and 294 are stars. The observed AGN redshift distribution is in good agreement with simulations based on empirical models for AGN activation and duty cycle. Forming composite spectra of type 1 AGN as a function of the mass and accretion rate of their black holes reveal systematic differences in the H-beta emission line profiles. This study paves the way towards systematic spectroscopic observation of sources to be discovered in the upcoming eROSITA survey over a large fraction of the sky.

[27]  arXiv:1912.03070 [pdf, ps, other]
Title: Hydrodynamic simulations unravel the progenitor-supernova-remnant connection in SN 1987A
Comments: Accepted for publication in Astronomy & Astrophysics, 20 pages, 13 figures, 5 tables
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

(Abridged) We aim at linking the dynamical and radiative properties of the remnant of SN 1987A to the geometrical and physical characteristics of the parent aspherical SN explosion and to the internal structure of its progenitor star. We performed 3D hydrodynamic simulations which describe the long-term evolution of SN 1987A from the onset of the SN to the full-fledged remnant at the age of 50 years, accounting for the pre-SN structure of the progenitor star. The simulations include all physical processes relevant for the complex phases of SN evolution and for the interaction of the SNR with the highly inhomogeneous ambient environment around SN 1987A. From the simulations, we synthesize observables to be compared with observations. By comparing the model results with observations, we constrained the initial SN anisotropy causing Doppler shifts observed in emission lines of heavy elements from ejecta, and leading to the remnant evolution observed in the X-ray band in the last 30 years. In particular, we found that the high mixing of ejecta unveiled by high redshifts and broadenings of [FeII] and $^{44}$Ti lines require a highly asymmetric SN explosion channeling a significant fraction of energy along an axis almost lying in the plane of the central equatorial ring around SN 1987A, roughly along the line-of-sight but with an offset of 40 deg, with the lobe propagating away from the observer slightly more energetic than the other. We found unambiguously that the observed distribution of ejecta and the dynamical and radiative properties of the SNR can be best reproduced if the structure of the progenitor star was that of a blue supergiant resulted from the merging of two massive stars.

[28]  arXiv:1912.03082 [pdf, ps, other]
Title: Analysis of Quiescent Corona X-ray Spectra from SphinX during the 2009 Solar Minimum
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The SphinX X-ray spectrophotometer on the {\em CORONAS-PHOTON}\/ mission observed the 1~--~15\,keV X-ray spectrum of the spatially integrated solar corona during the deep minimum of 2009, when solar activity was exceptionally low. Its sensitivity for energies $> 1.2$\,keV was higher than that of any other solar X-ray spectrometer in orbit at the time, including the detectors on GOES. Using much improved instrumental data than was used previously, we analyzed SphinX spectra in 576 intervals for which there was no discernible activity (NA), 40 intervals when there were X-ray brightenings (B), and sixteen intervals when there were micro-flares with peak emission less than GOES A1 (F). An instrumental background spectrum, formed over 34 hours of spacecraft night-time periods and including electronic noise and particle radiation, was subtracted from the solar spectra. Theoretical spectra were used to deduce temperatures on an isothermal assumption for the NA, B, and F intervals (1.69, 1.81, and 1.86\,MK respectively). Differential emission measure (DEM) analysis for the same spectra revealed a "cooler" component (log\,$T = 6.2$ or $T \approx 1.6$\,MK) in each case, but with a second hotter component having a less well-defined peak temperature varying from $\approx 2.5$ to $\approx 3.5$\,MK (log\,$T = 6.4$ and 6.55) and an emission measure between two and three orders smaller than that of the cooler component. These results are similar to those obtained at times just after solar minimum with the EVE instrument. A very hot component that might indicate the signature of nano-flare heating of the corona is not evident in SphinX data.

[29]  arXiv:1912.03116 [pdf, other]
Title: Mass and spin constraint on black holes in long GRBs
Comments: 3 pages, 2 figure, contribution to the Proceedings of the XXXIX Polish Astronomical Society Meeting (09-12 September 2019, Olsztyn, Poland
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We compute the evolution of a quasi-spherical, slowly rotating accretion flow around a black hole, whose mass and spin evolve adequately to the mass-energy transfer through the horizon. Our model is relevant for the central engine driving a long gamma ray burst, that originates from the collapse of a massive star. Our results show how much mass and spin a newly formed black hole should possess during collapsar to launch long GRB.

[30]  arXiv:1912.03117 [pdf, other]
Title: Probing dark matter via neutrino-gamma-ray correlations
Authors: Geoff Beck
Comments: 7 pages, 4 figures, submitted to proceedings of HEASA 2019
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The nature of dark matter is one of the most pressing questions in modern cosmology. Much work has been focussed in the past upon probing potential particle dark matter via gamma-rays resulting from its annihilation or decay. These processs are dominated by the decay of pions and thus have associated neutrino fluxes. Despite this, neutrino observations have been poor in thir ability to constrain the properties of hypothetical dark matter particles due to a lack of sensitivity. Since the gamma-ray and neutrino emissions from WIMP dark matter are expected to be correlated it becomes possible to infer an associated neutrino flux to accompany any gamma-ray flux that might be attributed to dark matter. In this work we will show that it is possible to derive superior and novel constraints, particularly on leptophilic and high mass WIMP models, with this approach. This is particularly relevant in the face of leptonic-related excesses observed in both the worlds of particle and astrophysics.

[31]  arXiv:1912.03118 [pdf, other]
Title: FeII strength in NLS1s -- dependence on the viewing angle and FWHM
Comments: 3 pages, 1 figure, Proceedings of the IAU356: Nuclear Activity in Galaxies across Cosmic Time, Addis Ababa, Ethiopia (7-11 October, 2019)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

We address the effect of orientation of the accretion disk plane and the geometry of the broad-line region (BLR) in the context of understanding the distribution of quasars along their Main Sequence. We utilize the photoionization code CLOUDY to model the BLR, incorporating the `un-constant' virial factor. We show the preliminary results of the analysis to highlight the co-dependence of the Eigenvector 1 parameter, $\mathrm{R_{FeII}}$ on the broad H$\beta$ FWHM (i.e. the line dispersion) and the inclination angle ($\theta$), assuming fixed values for the Eddington ratio ($\mathrm{L_{bol}}/\mathrm{L_{Edd}}$), black hole mass ($\mathrm{M_{BH}}$), spectral energy distribution (SED) shape, cloud density (n$\rm{_{H}}$) and composition.

[32]  arXiv:1912.03119 [pdf, other]
Title: FeII emission in NLS1s -- originating from denser regions with higher abundances?
Comments: 5 pages, 2 figures, Proceedings of the IAU356: Nuclear Activity in Galaxies across Cosmic Time, Addis Ababa, Ethiopia (7-11 October, 2019)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

The interpretation of the main sequence of quasars has become a frontier subject in the last years. The consider the effect of a highly flattened, axially symmetric geometry for the broad-line region (BLR) on the parameters related to the distribution of quasars along their Main Sequence. We utilize the photoionization code CLOUDY to model the BLR, assuming `un-constant' virial factor with a strong dependence on the viewing angle. We show the preliminary results of the analysis to highlight the co-dependence of the Eigenvector 1 parameter, R$_{\mathrm{FeII}}$ on the broad H$\beta$ FWHM (i.e. the line dispersion) and the inclination angle ($\theta$), assuming fixed values for the Eddington ratio ($\mathrm{L_{bol}}/\mathrm{L_{Edd}}$), black hole mass ($\mathrm{M_{BH}}$) and spectral energy distribution (SED) shape. We consider four cases with changing cloud density (n$\rm{_{H}}$) and composition. Understanding the FeII emitting region is crucial as this knowledge can be extended to the use of quasars as distance indicators for Cosmology.

[33]  arXiv:1912.03137 [pdf, other]
Title: Photo-processing of astro-PAHs
Authors: Christine Joblin (IRAP), Gabi Wenzel (IRAP), Sarah Rodriguez Castillo (IRAP), Aude Simon (MAD), Hassan Sabbah (IRAP), Anthony Bonnamy (IRAP), Dominique Toublanc (IRAP), Giacomo Mulas (OAC), Mingchao Ji (IRAP), Alexandre Giuliani (CEPIA), Laurent Nahon (SSOLEIL)
Journal-ref: Journal of Physics: Conference Series, IOP Publishing, In press
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chemical Physics (physics.chem-ph)

Polycyclic aromatic hydrocarbons (PAHs) are key species in astrophysical environments in which vacuum ultraviolet (VUV) photons are present, such as star-forming regions. The interaction with these VUV photons governs the physical and chemical evolution of PAHs. Models show that only large species can survive. However, the actual molecular properties of large PAHs are poorly characterized and the ones included in models are only an extrapolation of the properties of small and medium-sized species. We discuss here experiments performed on trapped ions including some at the SOLEIL VUV beam line DESIRS. We focus on the case of the large dicoronylene cation, C48H20+ , and compare its behavior under VUV processing with that of smaller species. We suggest that C2H2 is not a relevant channel in the fragmentation of large PAHs. Ionization is found to largely dominate fragmentation. In addition, we report evidence for a hydrogen dissociation channel through excited electronic states. Although this channel is minor, it is already effective below 13.6 eV and can significantly influence the stability of astro-PAHs. We emphasize that the competition between ionization and dissociation in large PAHs should be further evaluated for their use in astrophysical models.

[34]  arXiv:1912.03138 [pdf, other]
Title: A realistic two-dimensional model of Altair
Comments: 20 pages, 20 figures, accepted for publication in A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Fast rotation is responsible for important changes in the structure and evolution of stars. Optical long baseline interferometry now permits the study of its effects on the stellar surface, mainly gravity darkening and flattening. We aim to determine the fundamental parameters of the fast-rotating star Altair, in particular its evolutionary stage, mass, and differential rotation, using state-of-the-art stellar interior and atmosphere models together with interferometric, spectroscopic, and asteroseismic observations. We use ESTER 2D stellar models to produce the relevant surface parameters needed to create intensity maps from atmosphere models. Interferometric and spectroscopic observables are computed from these intensity maps and several stellar parameters are then adjusted using the MCMC algorithm Emcee. We determined Altair's equatorial radius to be 2.008 +/- 0.006 Rsun, the position angle 301.1 +/- 0.3 degrees, the inclination 50.7 +/- 1.2 degrees, and the equatorial angular velocity 0.74 +/- 0.01 times the Keplerian angular velocity. This angular velocity leads to a flattening of 0.220 +/- 0.003. We also deduce from the spectroscopically derived vsini ~ 243 km/s, a true equatorial velocity of ~314 km/s corresponding to a rotation period of 7h46m (~3 c/d). The data also impose a strong correlation between mass, metallicity, hydrogen abundance, and core evolution. Thanks to asteroseismic data, we constrain the mass of Altair to 1.86 +/- 0.03 Msun and further deduce its metallicity Z = 0.019 and its core hydrogen mass fraction Xc = 0.71, assuming an initial solar hydrogen mass fraction X = 0.739. These values suggest that Altair is ~100 Myrs old. Finally, the 2D ESTER model also gives the internal differential rotation of Altair, showing that its core rotates approximately 50% faster than the envelope, while the surface differential rotation does not exceed 6%.

[35]  arXiv:1912.03139 [pdf, other]
Title: A new approach to generate a catalogue of potential historical novae
Comments: 19 pages, 6 tables, 9+7 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Ancient Chinese, Korean and Vietnamese observers left us records of celestial sightings, the so-called `guest stars' dated up to $\sim2500$ years ago. Their identification with modern observable targets could open interesting insights into the long-term behavior of astronomical objects, as shown by the successful identification of 8 galactic supernovae (SNe). Here we evaluate the possibility to identify ancient classical novae with presently known cataclysmic variables (CVs). For this purpose, we have developed a method which reconsiders in detail positions and sizes of ancient asterisms, in order to define areas on the sky that should be used for a search of modern counterparts. These areas range from a few to several hundred square degrees, depending on the details given in ancient texts; they should replace the single coordinate values given by previous authors. Any appropriate target (CVs, X-ray binaries etc.) within these areas can be considered as a valid candidate for identification with the corresponding ancient event. Based on the original descriptions of several hundred old events, we selected those without movement and without a tail (to exclude comets) and which did not only visible within a certain hour (to exclude meteors). This way, we present a shortlist of 24 most promising events which could refer to classical nova eruptions. Our method is checked by applying it to the known SN identifications, leading to a margin of error between 0 and 4.5 degrees, meaning that some SN remnants lay exactly inside the areas given by the historical reports while in some other cases they are laying at considerable distances.

[36]  arXiv:1912.03218 [pdf, other]
Title: Stellar migration in galaxy discs using the Chirikov diffusion rate
Authors: Hervé Wozniak
Comments: 15 pages, 17 figures, Accepted for publication to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chaotic Dynamics (nlin.CD)

We are re-examining the problem of stellar migration in disc galaxies from a diffusion perspective. We use for the first time the formulation of the diffusion rates introduced by \citet{1979PhR....52..263C}, applied to both energy $E$ and angular momentum $L_\mathrm{z}$ in self-consistent N$-$body experiments. We limit our study to the evolution of stellar discs well after the formation of the bar, in a regime of adiabatic evolution. We show that distribution functions of Chirikov diffusion rates have similar shapes regardless the simulations, but different slopes for energy and angular momentum. Distribution functions of derived diffusion time scales $T_D$ have also the same form for all simulations, but are different for $T_D(E)$ and $T_D(L_\mathrm{z})$. Diffusion time scales are strongly dependent on $L_\mathrm{z}$. $T_D(E) \lesssim 1$~Gyr in a $L_\mathrm{z}$ range roughly delimited by the set of stellar bar resonances (between the Ultra Harmonic Resonance and the Outer Lindblad Resonance). Only particles with low $L_\mathrm{z}$ have $T_D(L_\mathrm{z}) \lesssim 10$ Gyr, i.e. the simulation length. In terms of mass fraction, 35 to 42% turn out to diffuse energy in a characteristic time scale shorter than 10 Gyr, i.e. simulations length, while 60 to 64% undergo the diffusion of the angular momentum on the same time scale. Both the diffusion of $L_\mathrm{z}$ and $E$ are important in order to grasp the full characterisation of the radial migration process, and we showed that depending on the spatial region considered, one or the other of the two diffusions dominates.

[37]  arXiv:1912.03233 [pdf, ps, other]
Title: Properties of galaxies with an offset between the position angles of the major kinematic and photometric axes
Comments: accepted for publication in Astronomy and Astrophysics
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We derive the photometric, kinematic, and abundance characteristics of 18 star-forming MaNGA galaxies with fairly regular velocity fields and surface brightness distributions and with a large offset between the measured position angles of the major kinematic and photometric axes, dPA > 20 degree. The aim is to examine if there is any other distinctive characteristic common to these galaxies. We found morphological signs of interaction in some (in 11 out of 18) but not in all galaxies. The observed velocity fields show a large variety; the maps of the isovelocities vary from an hourglass-like appearance to a set of straight lines. The position angles of the major kinematic axes of the stellar and gas rotations are close to each other. The values of the central oxygen abundance, radial abundance gradient, and star formation rate are distributed within the intervals defined by galaxies with small (no) dPA of similar mass. Thus, we do not find any specific characteristic common to all galaxies with large dPA. Instead, the properties of these galaxies are similar to those of galaxies with small (no) dPA. This suggests that either the reason responsible for the large dPA does not influence other characteristics or the galaxies with large dPA do not share a common origin, they can, instead, originate through different channels.

[38]  arXiv:1912.03239 [pdf, other]
Title: VLT/XShooter spectroscopy of Lyman Break Analogs: direct method O/H abundances and nitrogen enhancements
Comments: Resubmitted to ApJ following the first referee report (25 pages, 21 figures)
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We used VLT/XShooter to target a sample of nearby analogs of Lyman Break Galaxies (LBGs). These Lyman Break Analogs (LBAs) are similar to the LBGs in many of their physical properties. We determine electron temperatures using the weak [O III]4363 emission line, and determine the oxygen abundance (O/H) using the direct and strong line methods. We show that the direct and strong line abundances are consistent with established relations within ~0.2 dex. The analogs have nitrogen-to-oxygen ratios (N/O) and ionization parameters (q) that are, on average, offset with respect to typical local galaxies but similar to galaxies at z ~ 2 and other analogs. The N/O and q excesses correlate with the offsets observed in the strong line ratios, again similar to z ~ 2. The star formation rate surface densities are consistent with the high electron density and ionization, indicating that the interstellar medium (ISM) pressure is set by feedback from the starbursts. For a given O/H, the apparent N/O excess arises due to the offset in O/H with respect to the local mass-metallicity relation. This can be explained by recent inflow of relatively metal-poor gas which lowers O/H while leaving N/O unchanged. The difficulties in determining even basic ISM parameters in these nearby analogs illustrates some of the challenges we face at much higher redshifts, where similar rest-frame optical diagnostics for large samples of galaxies can be accessed with JWST.

[39]  arXiv:1912.03255 [pdf, other]
Title: Embedded operator splitting methods for perturbed systems
Authors: Hanno Rein
Comments: 7 pages, 4 figures, submitted to MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Dynamical Systems (math.DS)

It is common in classical mechanics to encounter systems whose Hamiltonian $H$ is the sum of an often exactly integrable Hamiltonian $H_0$ and a small perturbation $\epsilon H_1$ with $\epsilon\ll1$. Such near-integrability can be exploited to construct particularly accurate operator splitting methods to solve the equations of motion of $H$. However, in many cases, for example in problems related to planetary motion, it is computationally expensive to obtain the exact solution to $H_0$.
In this paper we present a new family of embedded operator splitting (EOS) methods which do not use the exact solution to $H_0$, but rather approximate it with yet another, embedded operator splitting method. Our new methods have all the desirable properties of classical methods which solve $H_0$ directly. But in addition they are very easy to implement and in some cases faster. When applied to the problem of planetary motion, our EOS methods have error scalings identical to that of the often used Wisdom-Holman method but do not require a Kepler solver, nor any coordinate transformations, or the allocation of memory. The only two problem specific functions that need to be implemented are the straight-forward kick and drift steps typically used in the standard second order leap-frog method.

[40]  arXiv:1912.03262 [pdf, other]
Title: CODEX clusters. The Survey, the Catalog, and Cosmology of the X-ray Luminosity Function
Comments: 10 pages, 11 figures, A&A submitted, part of SDSS DR16 data release
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Large area catalogs of galaxy clusters constructed from ROSAT All Sky Survey provide the base for our knowledge on the population of clusters thanks to the long-term multiwavelength efforts on their follow-up. Advent of large area photometric surveys superseding in depth previous all-sky data allows us to revisit the construction of X-ray cluster catalogs, extending the study to lower cluster masses and to higher redshifts and to provide the modelling of the selection function. We perform a wavelet detection of X-ray sources and make extensive simulations of the detection of clusters in the RASS data. We assign an optical richness to each of the 24,788 detected X-ray sources in the 10,382 square degrees of SDSS BOSS area, using redMaPPer version 5.2. We name this survey COnstrain Dark Energy with X-ray (CODEX) clusters. We show that there is no obvious separation of sources on galaxy clusters and AGN, based on distribution of systems on their richness. This is a combination of increasing number of galaxy groups and their selection as identification of an X-ray sources either by chance or due to groups hosting an AGN. To clean the sample, we use a cut on the optical richness at the level corresponding to the 10\% completeness of the survey and include it into the modelling of cluster selection function. We present the X-ray catalog extending to a redshift of 0.6. CODEX is the first large area X-ray selected catalog of Northern clusters reaching the fluxes of $10^{-13}$ ergs s$^{-1}$ cm$^{-2}$. We provide the modelling of the sample selection and discuss the redshift evolution of the high end of the X-ray luminosity function (XLF). Our results on $z<0.3$ XLF are in agreement with previous studies, while we provide new constraints on the $0.3<z<0.6$ XLF. We find a lack of strong redshift evolution of the XLF and consider possibilities to explain it within a flat $\Lambda$CDM.

[41]  arXiv:1912.03301 [pdf, other]
Title: Two Ultra-Faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey
Comments: 17 pages, 6 figures, submitted to AAS Journals
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We report the discovery of two ultra-faint stellar systems found in early data from the DECam Local Volume Exploration survey (DELVE). The first system, Centaurus I (DELVE J1238-4054), is identified as a resolved overdensity of old and metal-poor stars with a heliocentric distance of ${\rm D}_{\odot} = 116.3_{-0.6}^{+0.6}$ kpc, a half-light radius of $r_h = 2.3_{-0.3}^{+0.4}$ arcmin, an age of $\tau > 12.85$ Gyr, a metallicity of $Z = 0.0002_{-0.0002}^{+0.0001}$, and an absolute magnitude of $M_V = -5.55_{-0.11}^{+0.11}$ mag. This characterization is consistent with the population of ultra-faint satellites, and confirmation of this system would make Centaurus I one of the brightest recently discovered ultra-faint dwarf galaxies. Centaurus I is detected in Gaia DR2 with a clear and distinct proper motion signal, confirming that it is a real association of stars distinct from the Milky Way foreground; this is further supported by the clustering of blue horizontal branch stars near the centroid of the system. The second system, DELVE 1 (DELVE J1630-0058), is identified as a resolved overdensity of stars with a heliocentric distance of ${\rm D}_{\odot} = 19.0_{-0.6}^{+0.5} kpc$, a half-light radius of $r_h = 0.97_{-0.17}^{+0.24}$ arcmin, an age of $\tau = 12.5_{-0.7}^{+1.0}$ Gyr, a metallicity of $Z = 0.0005_{-0.0001}^{+0.0002}$, and an absolute magnitude of $M_V = -0.2_{-0.6}^{+0.8}$ mag, consistent with the known population of faint halo star clusters. Given the low number of probable member stars at magnitudes accessible with Gaia DR2, a proper motion signal for DELVE 1 is only marginally detected. We compare the spatial position and proper motion of both Centaurus I and DELVE 1 with simulations of the accreted satellite population of the Large Magellanic Cloud (LMC) and find that neither is likely to be associated with the LMC.

[42]  arXiv:1912.03302 [pdf, other]
Title: Milky Way Satellite Census -- I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1
Comments: 33 pages, 11 figures, 6 tables; submitted to the AAS Journals. Selection functions available at this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We report the results of a systematic search for ultra-faint Milky Way satellite galaxies using data from the Dark Energy Survey and Pan-STARRS1. Our search covers ~25,000 deg$^2$ of the high-Galactic-latitude sky reaching a 10$\sigma$ point-source depth of $\gtrsim$ 22.5 mag in the $g$ and $r$ bands. We do not detect any new high-significance satellite galaxy candidates, and we characterize the sensitivity of our search using a large set of simulated satellites injected into the survey data. We use these simulations to derive both analytic and machine-learning models that accurately predict the detectability of Milky Way satellites as a function of their distance, size, luminosity, and location on the sky. To demonstrate the utility of this observational selection function, we calculate the luminosity function of Milky Way satellite galaxies assuming that the known population of satellite galaxies is representative of the underlying distribution. We provide access to our observational selection function to facilitate comparisons with cosmological models of galaxy formation and evolution.

[43]  arXiv:1912.03303 [pdf, other]
Title: Milky Way Satellite Census -- II. Galaxy-Halo Connection Constraints Including the Impact of the Large Magellanic Cloud
Comments: 27 pages, 10 figures, 3 tables; submitted to the AAS Journals
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The population of Milky Way (MW) satellites contains the faintest known galaxies, and thus provides essential insight into galaxy formation and dark matter microphysics. Here, we combine a model of the galaxy--halo connection with newly derived observational selection functions based on searches for satellites in photometric surveys over nearly the entire high-Galactic-latitude sky. In particular, we use cosmological zoom-in simulations of MW-like halos that include realistic Large Magellanic Cloud (LMC) analogs to fit the position-dependent MW satellite luminosity function. We report decisive evidence for the statistical impact of the LMC on the MW satellite population due to an estimated $6.5\pm 1.5$ observed LMC-associated satellites, consistent with the number of LMC satellites inferred from $\textit{Gaia}$ proper motion measurements, confirming the predictions of cold dark matter models for the existence of satellites within satellite halos. Moreover, we infer that the LMC fell into the MW within the last $2\ \rm{Gyr}$ at high confidence. Based on our detailed full-sky modeling, we find that the faintest observed satellites inhabit halos with peak virial masses below $2.2\times 10^{8}\ M_{\rm{\odot}}$ at $95\%$ confidence, and we place the first robust constraints on the fraction of halos that host galaxies in this regime. We predict that the faintest detectable satellites occupy halos with peak virial masses above $10^{6}\ M_{\rm{\odot}}$, highlighting the potential for powerful galaxy formation and dark matter constraints from future dwarf galaxy searches.

Cross-lists for Mon, 9 Dec 19

[44]  arXiv:1912.01014 (cross-list from hep-ph) [pdf, other]
Title: Neutrino and positron constraints on spinning primordial black hole dark matter
Comments: v1: 8 pages, 6 figures. Comments welcome
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

Angular momentum is a fundamental property of a black hole and is known to have a strong effect on its evaporation rate. It has recently been postulated that primordial black holes can have substantial spin. We conduct a comprehensive study of the detectability of primordial black holes with non-negligible spin, via the searches for the diffuse supernova neutrino background and observation of the 511 keV gamma-ray line from positrons in the Galactic center, setting competitive constraints. Spinning primordial black holes are probed up to a slightly higher mass range compared to non-spinning ones. Our constraint using neutrinos is slightly weaker than that due to the diffuse gamma-ray background. We find that the positron constraints are typically weaker in the lower mass range and stronger in the higher mass range for the spinning primordial black holes compared to the non-spinning ones. They are generally stronger than those derived from the diffuse gamma-ray measurements for primordial black holes having masses greater than a few $\times \, 10^{16}$g.

[45]  arXiv:1912.02173 (cross-list from gr-qc) [pdf, ps, other]
Title: Black Hole Genesis and origin of cosmic acceleration
Comments: 4 pages
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We consider a hypothesis that the closed Universe was formed on the other side of the event horizon of a black hole existing in another universe. That black hole is seen in the Universe as a white hole, and its rest frame in comoving coordinates is a frame of reference in which the cosmic microwave background is isotropic. We consider the Lagrangian density for the gravitational field that is proportional to the curvature scalar, and use the metric-affine variational principle in which the symmetric affine connection and the metric tensor are variables. The white hole appears in the Lagrangian through a simplest covariant and linear term: the four-divergence of the four-velocity of the white hole in comoving coordinates. The variation of the action with respect to the connection generates the nonmetricity, which creates a term in the Lagrangian that is equivalent to a positive cosmological constant. The equation of motion of a test particle in the presence of this nonmetricity deviates from the geodesic equation by a term that depends on the four-velocities of the particle and the white hole. If these four-velocities are equal, then the equation of motion is geodesic. Consequently, the rest frame of reference of the white hole in comoving coordinates is the absolute inertial frame of reference. This hypothesis may therefore explain the origin of cosmic acceleration, known as dark energy, and the origin of inertia. In addition, it predicts deviations from the geodesic motion, which could explain possible anomalies in large-scale motion or anisotropies of cosmic acceleration.

[46]  arXiv:1912.02828 (cross-list from hep-ph) [pdf, other]
Title: Spontaneous Freeze Out of Dark Matter From an Early Thermal Phase Transition
Comments: 14 pages, 8 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

We propose a new paradigm for the thermal production of dark matter in the early universe, in which dark-matter particles acquire their mass and freeze out spontaneously from the thermal bath after a dark phase transition takes place. The decoupling arises because the dark-matter particles become suddenly non-relativistic and not because of any decay channel becoming kinematically close. We propose a minimal scenario in which a scalar and a fermionic dark-matter are in thermal equilibrium with the Standard-Model bath. We compute the finite temperature corrections to the scalar potential and identify a region of the parameter space where the fermionic dark-matter mass spontaneously jumps over the temperature when the dark phase transition happens. We explore the phenomenological implications of such a model in simple cases and show that the annihilation cross section of dark-matter particles has to be larger by more than one order of magnitude as compared to the usual constant-mass WIMP scenario in order to accomodate the correct relic abundance. We show that in the spontaneous freeze out regime a TeV-scale fermionic dark-matter that annihilates into leptons through s-wave processes can be accessible to detection in the near future.

[47]  arXiv:1912.02870 (cross-list from hep-ph) [pdf, other]
Title: Precision calculations of dark matter relic abundance
Comments: 20 pages, 12 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The dark matter annihilation channels sometimes involve sharp resonances. In such cases the usual momentum averaged approximations for computing the DM abundance may not be accurate. We develop an easily accessible momentum dependent framework for computing the DM abundance accurately and efficiently near such features. We apply the method to the case of a singlet scalar dark matter $s$ interacting with SM through higgs portal $\lambda_{\rm hs}s^2 h^2$ and compare the results with different momentum averaged methods. The accuracy of the latter depend strongly on the strength of the elastic interactions and corrections are large if WIMP has negligible interactions beyond the main annihilation channel. In the singlet scalar model however, the standard model scatterings induce an efficient kinetic equilibrium that validates the momentum averaged computation to 20 per cent accuracy. We update the current extent of the allowed region in the light singlet scalar dark matter to $m_{\rm S} \in [56,62.5]$ GeV.

[48]  arXiv:1912.02959 (cross-list from physics.space-ph) [pdf, other]
Title: Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe
Comments: Accepted for publication in The Astrophysical Journal Supplement, PSP special issue
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph)

Direct evidence of an inertial-range turbulent energy cascade has been provided by spacecraft observations in heliospheric plasmas. In the solar wind, the average value of the derived heating rate near 1 au is $\sim 10^{3}\, \mathrm{J\,kg^{-1}\,s^{-1}}$, an amount sufficient to account for observed departures from adiabatic expansion. Parker Solar Probe (PSP), even during its first solar encounter, offers the first opportunity to compute, in a similar fashion, a fluid-scale energy decay rate, much closer to the solar corona than any prior in-situ observations. Using the Politano-Pouquet third-order law and the von K\'arm\'an decay law, we estimate the fluid-range energy transfer rate in the inner heliosphere, at heliocentric distance $R$ ranging from $54\,R_{\odot}$ (0.25 au) to $36\,R_{\odot}$ (0.17 au). The energy transfer rate obtained near the first perihelion is about 100 times higher than the average value at 1 au. This dramatic increase in the heating rate is unprecedented in previous solar wind observations, including those from Helios, and the values are close to those obtained in the shocked plasma inside the terrestrial magnetosheath.

[49]  arXiv:1912.02976 (cross-list from hep-ph) [pdf, other]
Title: Hunting the Glashow Resonance with PeV Neutrino Telescopes
Comments: 12 pages, 7 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

The Glashow resonant scattering, $i.e$. ${\overline{\nu}^{}_{e} + e^{-} \rightarrow W^{-} \rightarrow \text{anything}}$, offers us a possibility of disentangling $\overline{\nu}^{}_{e}$ from the total astrophysical neutrino fluxes. Meanwhile, a great number of high-energy neutrino telescopes, with various detection mechanisms, are advancing towards a better understanding of one of the most energetic frontiers of the Universe. In this work, we investigate a connection between through-going muons at IceCube and the Glashow resonance signal through the channel $W^{-} \rightarrow \mu$. We find that for IceCube, muons from $\overline{\nu}^{}_{e}$ can induce a $\sim20\%$ excess of PeV events around the horizontal direction. However, the current statistic of IceCube is not enough to observe such an excess. We also address the novel possibility of $\overline{\nu}^{}_{e}$ detection via $W^{-} \rightarrow \tau$ at telescopes aiming to detect Earth-skimming and mountain-penetrating neutrinos. The subsequent hadronic decay of a tau will induce an extensive air shower which can be detected by telescopes with Cherenkov or fluorescence techniques. Similar to IceCube, it is challenging to observe the Glashow resonance excess from the Earth-skimming neutrinos. Nevertheless, we find it is promising to observe Glashow resonance events with a mountain as the target.

[50]  arXiv:1912.03162 (cross-list from hep-th) [pdf, ps, other]
Title: Non-flat Universes and Black Holes in Asymptotically Free Mimetic Gravity
Comments: 55 pages, 3 figures
Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

The recently proposed theory of "Asymptotically Free Mimetic Gravity" is extended to the general non-homogeneous, spatially non-flat case. We present a modified theory of gravity which is free of higher derivatives of the metric. In this theory asymptotic freedom of gravity implies the existence of a minimal black hole with vanishing Hawking temperature. Introducing a spatial curvature dependent potential, we moreover obtain non-singular, bouncing modifications of spatially non-flat Friedmann and Bianchi universes.

[51]  arXiv:1912.03240 (cross-list from physics.space-ph) [pdf, other]
Title: Magnetic field kinks and folds in the solar wind
Comments: Accepted for publication on APJ PSP special issue
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)

Parker Solar Probe (PSP) observations during its first encounter at 35.7 $R_\odot$ have shown the presence of magnetic field lines which are strongly perturbed to the point that they produce local inversions of the radial magnetic field, known as switchbacks. Their counterparts in the solar wind velocity field are local enhancements in the radial speed, or jets, displaying (in all components) the velocity-magnetic field correlation typical of large amplitude Alfv\'en waves propagating away from the Sun. Switchbacks and radial jets have previously been observed over a wide range of heliocentric distances by Helios, WIND and Ulysses, although they were prevalent in significantly faster streams than seen at PSP. Here we study via numerical MHD simulations the evolution of such large amplitude Alfv\'enic fluctuations by including, in agreement with observations, both a radial magnetic field inversion and an initially constant total magnetic pressure. Despite the extremely large excursion of magnetic and velocity fields, switchbacks are seen to persist for up to hundreds of Alfv\'en crossing times before eventually decaying due to the parametric decay instability. Our results suggest that such switchback/jet configurations might indeed originate in the lower corona and survive out to PSP distances, provided the background solar wind is sufficiently calm, in the sense of not being pervaded by strong density fluctuations or other gradients, such as stream or magnetic field shears, that might destabilize or destroy them over shorter timescales.

[52]  arXiv:1912.03245 (cross-list from hep-ph) [pdf, other]
Title: BSM with Cosmic Strings: Heavy, up to EeV mass, Unstable Particles
Comments: 27 pages, 9 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Unstable heavy particles well above the TeV scale are unaccessible experimentally. So far, Big-Bang Nucleosynthesis (BBN) provides the strongest limits on their mass and lifetime, the latter being shorter than 0.1 second. We show how these constraints could be potentially tremendously improved by the next generation of Gravitational-Wave (GW) interferometers, extending to lifetimes as short as $10^{-16}$ second. The key point is that these particles may have dominated the energy density of the universe and have triggered a period of matter domination at early times, until their decay before BBN. The resulting modified cosmological history compared to the usually-assumed single radiation era would imprint observable signatures in stochastic gravitational-wave backgrounds of primordial origin. In particular, we show how the detection of the GW spectrum produced by long-lasting sources such as cosmic strings would provide a unique probe of particle physics parameters. When applied to specific particle production mechanisms in the early universe, these GW spectra could be used to derive new constraints on many UV extensions of the Standard Model. We illustrate this on a few examples, such as supersymmetric models where the mass scale of scalar moduli and gravitino can be constrained up to $10^{10}$ GeV. Further bounds can be obtained on the reheating temperature of models with only-gravitationally-interacting particles as well as on the kinetic mixing of heavy dark photons at the level of $10^{-18}$.

[53]  arXiv:1912.03300 (cross-list from hep-ph) [pdf, other]
Title: The hadronic interaction model Sibyll 2.3c and extensive air showers
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE)

We present a new version of the hadron interaction event generator Sibyll. While the core ideas of the model have been preserved, the new version handles the production of baryon pairs and leading particles in a new way. In addition, production of charmed hadrons is included. Updates to the model are informed by high-precision measurements of the total and inelastic cross sections with the forward detectors at the LHC that constrain the extrapolation to ultra-high energy. Minimum-bias measurements of particle spectra and multiplicities support the tuning of fragmentation parameters. This paper demonstrates the impact of these changes on air shower observables such as $X_{\rm max}$ and $N_\mu$, drawing comparisons with other contemporary cosmic ray interaction models.

Replacements for Mon, 9 Dec 19

[54]  arXiv:0910.2778 (replaced) [pdf, ps, other]
Title: Determining planetary positions in the sky for ~50 years to an accuracy of 1 degree with a calculator
Comments: 15 pages, 4 figures, 4 tables
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
[55]  arXiv:1610.07783 (replaced) [pdf, ps, other]
Title: GMRT observations of IC 711 -- The longest head-tail radio galaxy known
Comments: 14 pages. 12 figures, 3 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[56]  arXiv:1709.08302 (replaced) [pdf]
Title: Methane release on Early Mars by atmospheric collapse and atmospheric reinflation
Comments: Accepted by Planetary and Space Science
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[57]  arXiv:1902.01538 (replaced) [pdf, other]
Title: Detectability of modulated X-rays from LISA's supermassive black hole mergers
Comments: 16 pages, 12 figures. Version accepted for publication on ApJ
Journal-ref: ApJ 886 146 (2019)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[58]  arXiv:1903.00023 (replaced) [pdf, other]
Title: Spectroscopic QUasar Extractor and redshift (z) EstimatorSQUEzE I: Methodology
Comments: 11 pages, 9 figures, 5 tables, accepted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[59]  arXiv:1903.04957 (replaced) [pdf, other]
Title: Sheer shear: weak lensing with one mode
Comments: 15 pages, 16 figures. Accepted version on OJA
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[60]  arXiv:1903.06174 (replaced) [pdf, other]
Title: Thermal stability of winds driven by radiation pressure in super-Eddington accretion disks
Comments: 17 pages, 9 figures, 5 tables, accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM); Computational Physics (physics.comp-ph)
[61]  arXiv:1903.10414 (replaced) [pdf, other]
Title: Statistical study of hard X-ray emitting electrons associated with flare-related coronal jets
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[62]  arXiv:1903.10563 (replaced) [pdf, other]
Title: Machine learning and the physical sciences
Journal-ref: Rev. Mod. Phys. 91, 045002 (2019)
Subjects: Computational Physics (physics.comp-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Disordered Systems and Neural Networks (cond-mat.dis-nn); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
[63]  arXiv:1904.07757 (replaced) [pdf, other]
Title: Stochastic gravitational wave background anisotropies in the mHz band: astrophysical dependencies
Comments: 6 pages, 4 figures; accepted in MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
[64]  arXiv:1904.11294 (replaced) [pdf, other]
Title: A robust measurement of the first higher-derivative bias of dark matter halos
Comments: 26 pages, 9 figures; v2: minor modifications through the paper and on fig.7. Version accepted by JCAP
Journal-ref: JCAP 11 (2019) 041
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[65]  arXiv:1904.12903 (replaced) [pdf, other]
Title: Modified Gravity Away from a $Λ$CDM Background
Comments: 14 pages, 13 figures. Matches published version in JCAP, LCDM discussion added
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[66]  arXiv:1906.12228 (replaced) [pdf, other]
Title: Kinetic and internal energy transfer in implicit large eddy simulations of forced compressible turbulence
Comments: accepted for publication in Phys. Rev. E, 20 pages, 14 figures
Journal-ref: Phys. Rev. E 100, 043116 (2019)
Subjects: Fluid Dynamics (physics.flu-dyn); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
[67]  arXiv:1907.08211 (replaced) [pdf, other]
Title: Data Analysis for Precision 21 cm Cosmology
Comments: 105 pages, 16 figures; Invited review for PASP; v2: replaced with accepted PASP version
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[68]  arXiv:1907.11846 (replaced) [pdf, other]
Title: Hazma: A Python Toolkit for Studying Indirect Detection of Sub-GeV Dark Matter
Comments: Minor revisions; fixed typos in FSR spectra
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Computational Physics (physics.comp-ph)
[69]  arXiv:1908.00546 (replaced) [pdf, other]
Title: LISA for Cosmologists: Calculating the Signal-to-Noise Ratio for Stochastic and Deterministic Sources
Comments: V2: added 'monotone' example (white-dwarf binary ZTFJ1539) and other minor changes to match published version. 15 page, 4 figures, comments welcome, Mathematica notebook outlining main calculations at this https URL
Journal-ref: Phys. Rev. D 100, 104055 (2019)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[70]  arXiv:1908.00795 (replaced) [pdf, other]
Title: Exact joint likelihood of pseudo-$C_\ell$ estimates from correlated Gaussian cosmological fields
Comments: 17 pages, 7 figures. Updated to match accepted version
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (physics.data-an); Applications (stat.AP)
[71]  arXiv:1908.03989 (replaced) [pdf, other]
Title: As A Matter of State: The role of thermodynamics in magnetohydrodynamic turbulence
Comments: 16 pages, 7 figures, accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Fluid Dynamics (physics.flu-dyn); Plasma Physics (physics.plasm-ph)
[72]  arXiv:1908.05765 (replaced) [pdf, other]
Title: The impact of the observed baryon distribution in haloes on the total matter power spectrum
Authors: Stijn N.B. Debackere, Joop Schaye, Henk Hoekstra (Leiden Observatory)
Comments: 21 pages, 19 figures, accepted for publication in MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
[73]  arXiv:1908.08057 (replaced) [pdf, other]
Title: Bias to CMB lensing from lensed foregrounds
Comments: Version accepted in PRD. Code available at this https URL
Journal-ref: Phys. Rev. D 100, 123504 (2019)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
[74]  arXiv:1908.10682 (replaced) [pdf, other]
Title: Explaining the low luminosity of Uranus: A self-consistent thermal and structural evolution
Authors: A. Vazan, R. Helled
Comments: 10 pages, 7 figures, accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[75]  arXiv:1909.02323 (replaced) [pdf, other]
Title: Radio and X-ray monitoring of the accreting millisecond X-ray pulsar IGR J17591-2342 in outburst
Comments: 12 pages, 3 figures, 2 tables, accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[76]  arXiv:1910.01163 (replaced) [pdf, other]
Title: Evolution of giant molecular clouds across cosmic time
Comments: 15 pages, 11 figures Submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[77]  arXiv:1910.09557 (replaced) [pdf, ps, other]
Title: Gravitational waves and higher dimensions: Love numbers and Kaluza-Klein excitations
Comments: 8 pages, RevTeX 4. v2: Minor corrections, version to appear in Physical Review D
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
[78]  arXiv:1910.11288 (replaced) [pdf, other]
Title: Rapid bound-state formation of Dark Matter in the Early Universe
Comments: 9 pages, 2 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[79]  arXiv:1911.08488 (replaced) [pdf, other]
[80]  arXiv:1912.00785 (replaced) [pdf, other]
Title: Gauge Independence of Induced Gravitational Waves
Comments: 16 pages, 1 figure; minor changes, references added
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)
[81]  arXiv:1912.01005 (replaced) [pdf, other]
Title: AVIATOR: Morphological object reconstruction in 3D. An application to dense cores
Comments: 11 pages, 16 figures, accepted for publication by Astronomy & Astrophysics. v2: Typo in Eq. 3 corrected. The AVIATOR code and a Jupyter notebook illustrating its use is publicly available at this https URL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)
[82]  arXiv:1912.01863 (replaced) [pdf, other]
Title: Evolution of the Alfvén Mach number associated with a coronal mass ejection shock
Comments: 8 pages, 4 figures
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
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