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

Astrophysics

New submissions

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New submissions for Wed, 27 Nov 19

[1]  arXiv:1911.11140 [pdf, other]
Title: The Metallicity Gradient and Complex Formation History of the Outermost Halo of the Milky Way
Comments: 11 pages, 5 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We present an examination of the metallicity distribution function of the outermost stellar halo of the Galaxy based on an analysis of both local (within 4 kpc of the Sun, ~16,500 stars) and non-local (~21,700 stars) samples. These samples were compiled using spectroscopic metallicities from the Sloan Digital Sky Survey and photometric metallicities from the SkyMapper Southern Survey. We detect a negative metallicity gradient in the outermost halo (r > 35 kpc from the Galactic center), and find that the frequency of very metal-poor ([Fe/H] < -2.0) stars in the outer-halo region reaches up to ~60% in our most distant sample, commensurate with previous theoretical predictions. This result provides clear evidence that the outer-halo formed hierarchically. The retrograde stars in the outermost halo exhibit a roughly constant metallicity, which may be linked to the accretion of the Sequoia progenitor. In contrast, prograde stars in the outermost halo exhibit a strong metallicity-distance dependence, indicating that they likely originated from the accretion of galaxies less massive than the Sequoia progenitor galaxy.

[2]  arXiv:1911.11142 [pdf, other]
Title: GW170817A as a Hierarchical Black Hole Merger
Comments: 6 pages, 3 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Despite the rapidly growing number of stellar-mass binary black hole mergers discovered through gravitational waves, the origin of these binaries is still not known. In galactic centers, black holes can be brought to each others' proximity by dynamical processes, resulting in mergers. It is also possible that black holes formed in previous mergers encounter new black holes, resulting in so-called hierarchical mergers. Hierarchical events carry signatures such as higher-than usual black hole mass and spin. Here we show that the recently reported gravitational-wave candidate, GW170817A, could be the result of such a hierarchical merger. In particular, its chirp mass $\sim40$ M$_\odot$ and effective spin of $\chi_{\rm eff}\sim0.5$ are the typically expected values from hierarchical mergers within the disks of active galactic nuclei. While we cannot rule out an isolated-binary origin, our results are suggestive (albeit not definitive, with a Bayes factor of $\sim10$), especially together with the binary merger GW170729, that some gravitational-wave observations may come from hierarchical mergers.

[3]  arXiv:1911.11144 [pdf, other]
Title: Probing the Small-Scale Matter Power Spectrum with Large-Scale 21-cm Data
Comments: 23 pages, 17 figures. Comments are welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

The distribution of matter fluctuations in our universe is key for understanding the nature of dark matter and the physics of the early cosmos. Different observables have been able to map this distribution at large scales, corresponding to wavenumbers $k\lesssim 10$ Mpc$^{-1}$, but smaller scales remain much less constrained. The 21-cm line is a promising tracer of early stellar formation, which took place in small haloes (with masses $M\sim 10^6-10^8M_\odot$), formed out of matter overdensities with wavenumbers as large as $k\approx100$ Mpc$^{-1}$. Here we forecast how well both the 21-cm global signal, and its fluctuations, could probe the matter power spectrum during cosmic dawn ($z=12-25$). We find that the long-wavelength modes (with $k\lesssim40$ Mpc$^{-1}$) are highly degenerate with astrophysical parameters, whereas the modes with $k= (40-80)$ Mpc$^{-1}$ are more readily observable. This is further illustrated in terms of the principal components of the matter power spectrum, which peak at $k\sim 50$ Mpc$^{-1}$ both for a typical experiment measuring the 21-cm global signal and its fluctuations. We find that, imposing broad priors on astrophysical parameters, a global-signal experiment can measure the amplitude of the matter power spectrum integrated over $k= (40-80)$ Mpc$^{-1}$ with a precision of tens of percent. A fluctuation experiment, on the other hand, can constrain the power spectrum to a similar accuracy over both the $k=(40-60)$ Mpc$^{-1}$ and $(60-80)$ Mpc$^{-1}$ ranges even without astrophysical priors. The constraints outlined in this work would be able to test the behavior of dark matter at the smallest scales yet measured, for instance probing warm-dark matter masses up to $m_{\rm WDM}=8$ keV for the global signal and $14$ keV for the 21-cm fluctuations. This could shed light on the nature of dark matter beyond the reach of other cosmic probes.

[4]  arXiv:1911.11148 [pdf, other]
Title: Probing the Weak Gravity Conjecture in the Cosmic Microwave Background
Comments: 29 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

The weak gravity conjecture imposes severe constraints on natural inflation. A trans-Planckian axion decay constant can only be realized if the potential exhibits an additional (subdominant) modulation with sub-Planckian periodicity. The resulting wiggles in the axion potential generate a characteristic modulation in the scalar power spectrum of inflation which is logarithmic in the angular scale. The compatibility of this modulation is tested against the most recent Cosmic Microwave Background (CMB) data by Planck and BICEP/Keck. Intriguingly, we find that the modulation completely resolves the tension of natural inflation with the CMB. A Bayesian model comparison reveals that natural inflation with modulations describes all existing data equally well as the cosmological standard model $\Lambda$CDM. In addition, the bound of a tensor-to-scalar ratio r > 0.002 correlated with a striking small-scale suppression of the scalar power spectrum occurs. Future CMB experiments could directly probe the modulation through their improved sensitivity to smaller angular scales and possibly the measurement of spectral distortions. They could, thus, verify a key prediction of the weak gravity conjecture and provide dramatic new insights into the theory of quantum gravity.

[5]  arXiv:1911.11149 [pdf, other]
Title: A New Microquasar Candidate in M83
Comments: Accepted by ApJ. Size = 8 MB
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Microquasars are neutron star or black hole X-ray binaries with jets. These jets can create shock-ionized bubbles of hot plasma that can masquerade as peculiar supernova remnants (SNRs) in extragalactic surveys. To see if this is the case in the well-studied spiral galaxy M83, where one microquasar candidate (M83-MQ1) has already been identified, we studied the properties of nine SNR candidates, selected because of their elongated or irregular morphology, from the set of previously identified SNRs in that galaxy. Using multiwavelength data from Chandra, the Hubble Space Telescope, Gemini, and the Australia Telescope Compact Array, we found that at least six of our nine sources are best interpreted as SNRs. For one source, we do not have enough observational data to explain its linear morphology. Another source shows a nebular optical spectrum dominated by photo-ionization by O stars, but its excess [Fe II] and radio luminosity suggest a possible hidden SNR. Finally, one source (S2) shows an elongated structure of ionized gas, two radio sources along that line, and an accretion-powered X-ray source in between them (the Chandra source L14-139). While S2 could be a chance alignment of multiple SNRs and one X-ray binary, it seems more likely that it is a single physical structure powered by the jet from the accreting compact object. In the latter case, the size and luminosity of S2 suggest a kinetic power of around 10^{40} erg/s, in the same class as the most powerful microquasars in the local universe (e.g., S26 in NGC7793 and SS433 in our own Galaxy).

[6]  arXiv:1911.11150 [pdf, other]
Title: Early Structure Formation Constraints on the Ultra-Light Axion in the Post-Inflation Scenario
Comments: 15 pages, 8 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)

Many works have concentrated on the observable signatures of the dark matter being an ultralight axion-like particle (ALP). We concentrate on a particularly dramatic signature in the late-time cosmological matter power spectrum that occurs if the symmetry breaking that establishes the ALP happens after inflation -- white-noise density fluctuations that dominate at small scales over the adiabatic fluctuations from inflation. These fluctuations alter the early history of nonlinear structure formation. We find that for symmetry breaking scales of $f_A \sim 10^{13}-10^{15}$GeV, which requires a high effective maximum temperature after inflation, ALP dark matter with particle mass of $m_A \sim 10^{-13}-10^{-20}$eV could significantly change the number of high-redshift dwarf galaxies, the reionization history, and the Ly$\alpha$ forest. We consider all three observables. We find that the Ly$\alpha$ forest is the most constraining of current observables, excluding $f_A \gtrsim 10^{15}$GeV ($m_A \lesssim 10^{-17}$eV) in the simplest model for the ALP and considerably lower values in models coupled to a hidden strongly interacting sector ($f_A \gtrsim 10^{13}$GeV and $m_A \lesssim 10^{-13}$eV). Observations that constrain the extremely high-redshift tail of reionization may disfavor similar levels of isocurvature fluctuations as the forest. Future $z\sim 20-30$ 21cm observations have the potential to improve these constraints further using that the supersonic motions of the isocurvature-enhanced abundance of $\sim10^4M_\odot$ halos would shock heat the baryons, sourcing large BAO features.

[7]  arXiv:1911.11152 [pdf, other]
Title: The dry and carbon poor inner disk of TW Hya: evidence for a massive icy dust trap
Comments: 6 pages, 3 figures, accepted to A&A letters
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

Gas giants accrete their envelopes from the gas and dust of proto-planetary disks, so it is important to determine the composition of the inner few AU, where most giant planets are expected to form. We aim to constrain the elemental carbon and oxygen abundance in the inner disk ($R<$2.3 AU) of TW Hya and compare with the outer disk ($R>2.3$ AU) where carbon and oxygen appear underabundant by a factor of $\sim$50. Archival infrared observations of TW Hya are compared with a detailed thermo-chemical model, DALI. The inner disk gas mass and elemental C and O abundances are varied to fit the infrared CO, H$_2$ and H$_2$O line fluxes. Best fitting models have an inner disk that has a gas mass of $ 2 \times 10^{-4} M_\odot$ with C/H $\approx 3 \times 10^{-6}$ and O/H $\approx 6 \times 10^{-6}$. The elemental oxygen and carbon abundances of the inner disk are $\sim 50$ times underabundant compared to the ISM and are consistent with those found in the outer disk. The uniformly low volatile abundances imply that the inner disk is not enriched by ices on drifting bodies that evaporate. This indicates that drifting grains are stopped in a dust trap outside the water ice line. Such a dust trap would also form a cavity as seen in high resolution sub-millimeter continuum observations. If CO is the major carbon carrier in the ices, dust needs to be trapped efficiently outside the CO ice line of $\sim$20 AU. This would imply that the shallow sub-millimeter rings in the TW Hya disk outside of 20 AU correspond to very efficient dust traps. The more likely scenario is that more than 98\% of the CO has been converted into less volatile species, e.g. CO$_2$ and CH$_3$OH. A giant planet forming in the inner disk would be accreting gas with low carbon and oxygen abundances as well as very little icy dust, potentially leading to a planet atmosphere with strongly substellar C/H and O/H ratios.

[8]  arXiv:1911.11154 [pdf, other]
Title: Jupiter formed as a pebble pile around the N$_2$ ice line
Comments: 5 pages, 2 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

The region around the H$_2$O ice line, due to its higher surface density, seems to be the ideal location to form planets. The core of Jupiter, as well as the cores of close in gas giants are thus thought to form in this region of the disk. Actually constraining the formation location of individual planets has proven to be difficult, however. We aim to use the Nitrogen abundance in Jupiter, which is around 4 times solar, in combination with \textit{Juno} constraints on the total mass of heavy elements in Jupiter, to narrow down its formation scenario. Different pathways of enrichment of Jupiter's atmosphere, such as the accretion of enriched gas, pebbles or planetesimals are considered and their implications for the oxygen abundance of Jupiter is discussed. The super solar Nitrogen abundance in Jupiter necessitates the accretion of extra N$_2$ from the proto-solar nebula. The only location of the disk that this can happen is outside, or just inside the N$_2$ ice line. These constraints favor a pebble accretion origin of Jupiter, both from the composition as well as from a planet formation perspective. We predict that Jupiter's oxygen abundance is between 3.6 and 4.5 times solar.

[9]  arXiv:1911.11158 [pdf, other]
Title: Fisher for complements: Extracting cosmology and neutrino mass from the counts-in-cells PDF
Comments: 21 pages, 24 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We comprehensively analyse the cosmology dependence of counts-in-cell statistics. We focus on the shape of the one-point probability distribution function (PDF) of the matter density field at mildly nonlinear scales. Based on large-deviation statistics, we parametrise the cosmology dependence of the matter PDF in terms of the linear power spectrum, the growth factor, the spherical collapse dynamics, and the nonlinear variance. We extend our formalism to include massive neutrinos, finding that the total matter PDF is highly sensitive to the total neutrino mass $M_\nu$ and can disentangle it from the clustering amplitude $\sigma_8$. Using more than a million PDFs extracted from the Quijote simulations, we determine the response of the matter PDF to changing parameters in the $\nu\Lambda$CDM model and successfully cross-validate the theoretical model and the simulation measurements. We present the first $\nu\Lambda$CDM Fisher forecast for the matter PDF at multiple scales and redshifts, and its combination with the matter power spectrum. We establish that the matter PDF and the matter power spectrum are highly complementary at mildly nonlinear scales. The matter PDF is particularly powerful for constraining the matter density $\Omega_m$, clustering amplitude $\sigma_8$ and the total neutrino mass $M_\nu$. Adding the mildly nonlinear matter PDF to the mildly nonlinear matter power spectrum improves constraints on $\Omega_m$ by a factor of 5 and $\sigma_8$ by a factor of 2 when considering the three lowest redshifts. In our joint analysis of the matter PDF and matter power spectrum at three redshifts, the total neutrino mass is constrained to better than 0.01 eV with a total volume of 6 (Gpc/h)$^3$. We discuss how density-split statistics can be used to translate those encouraging results for the matter PDF into realistic observables in galaxy surveys.

[10]  arXiv:1911.11163 [pdf, other]
Title: Magnetising the circumgalactic medium of disk galaxies
Comments: 12 pages, 12 figures, submitted to MNRAS, comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The circumgalactic medium (CGM) is one of the frontiers of galaxy formation and intimately connected to the galaxy via accretion of gas on to the galaxy and gaseous outflows from the galaxy. Here we analyse the magnetic field in the CGM of the Milky Way-like galaxies simulated as part of the \textsc{Auriga} project that constitutes a set of high resolution cosmological magnetohydrodynamical zoom simulations. We show that at high redshift the CGM becomes magnetised via galactic outflows that transport magnetised gas from the disk into the halo. At this time the magnetisation of the CGM closely follows its metal enrichment. We then show that at low redshift an in-situ turbulent dynamo that operates on a timescale of Gigayears further amplifies the magnetic field in the CGM and sets its strength down $z=0$. The magnetic field strength reaches a typical value of $0.1\,\mu G$ at the virial radius at $z=0$ and becomes mostly uniform within the virial radius. Its Faraday rotation signal is in excellent agreement with recent observations. For most of its evolution the magnetic field in the CGM is an unordered small scale field. Only strong coherent outflows at low redshift are able to order the magnetic field in parts of the CGM that are directly displaced by these outflows.

[11]  arXiv:1911.11165 [pdf, other]
Title: X-ray Signatures of Black Hole Feedback: Hot Galactic Atmospheres in IllustrisTNG and X-ray Observations
Comments: 19 pages, 10 figures, 2 tables, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Hot gaseous atmospheres that permeate galaxies and extend far beyond their stellar distribution, where they are commonly referred to as the circumgalactic medium (CGM), imprint important information about feedback processes powered by the stellar populations of galaxies and their central supermassive black holes (SMBH). In this work we study the properties of this hot X-ray emitting medium using the IllustrisTNG cosmological simulations. We analyse their mock X-ray spectra, obtained in TNG100 and TNG50, and compare the results with X-ray observations of nearby early-type galaxies. The simulations reproduce the observed X-ray luminosities ($L_{\rm X}$) and temperature ($T_{\rm X})$ at small ($<R_{\rm e}$) and intermediate ($<5R_{\rm e}$) radii reasonably well. We find that the X-ray properties of lower mass galaxies depend on their star formation rates. In particular, in the magnitude range where the star-forming and quenched populations overlap, $M_{\rm K}\sim-24$ $ (M_*\sim10^{10.7}M_\odot)$, we find that the X-ray luminosities of star-forming galaxies are on average about an order of magnitude higher than those of their quenched counterparts. We show that this diversity in $L_{\rm X}$ is a direct manifestation of the quenching mechanism in the simulations, where the galaxies are quenched due to gas expulsion driven by SMBH kinetic feedback. The observed dichotomy in $L_{\rm X}$ is thus an important observable prediction for the SMBH feedback-based quenching mechanisms implemented in state-of-the-art cosmological simulations. While the current X-ray observations of star forming galaxies are broadly consistent with the predictions of the simulations, the observed samples are small and more decisive tests are expected from the sensitive all-sky X-ray survey with eROSITA.

[12]  arXiv:1911.11194 [pdf, other]
Title: The dynamically young outflow of the Class 0 protostar Cha-MMS1
Comments: Accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

On the basis of its low luminosity, its chemical composition, and the absence of a large-scale outflow, the dense core Cha-MMS1 located in the Chamaeleon I molecular cloud was proposed as a first hydrostatic core (FHSC) candidate a decade ago. Our goal is to test this hypothesis by searching for a slow, compact outflow driven by Cha-MMS1 that would match the predictions of MHD simulations for this short phase of star formation. We use the Atacama Large Millimetre/submillimetre Array (ALMA) to map Cha-MMS1 at high angular resolution in CO 3-2 and 13CO 3-2 as well as in continuum emission. We report the detection of a bipolar outflow emanating from the central core, along a (projected) direction roughly parallel to the filament in which Cha-MMS1 is embedded and perpendicular to the large-scale magnetic field. The morphology of the outflow indicates that its axis lies close to the plane of the sky. We measure velocities corrected for inclination of more than 90km/s which is clearly incompatible with the expected properties of a FHSC outflow. Several properties of the outflow are determined and compared to previous studies of Class 0 and Class I protostars. The outflow of Cha-MMS1 has a much smaller momentum force than the outflows of other Class 0 protostars. In addition, we find a dynamical age of 200-3000yr indicating that Cha-MMS1 might be one of the youngest ever observed Class 0 protostars. While the existence of the outflow suggests the presence of a disk, no disk is detected in continuum emission and we derive an upper limit of 55au to its radius. We conclude that Cha-MMS1 has already gone through the FHSC phase and is a young Class 0 protostar, but it has not brought its outflow to full power yet.

[13]  arXiv:1911.11210 [pdf, other]
Title: Robust diffraction-limited NIR-to-NUV wide-field imaging from stratospheric balloon-borne platforms -- SuperBIT science telescope commissioning flight & performance
Comments: The following article has been submitted to Review of Scientific Instruments (RSI)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

At a fraction the total cost of an equivalent orbital mission, scientific balloon-borne platforms, operating above 99.7% of the Earth's atmosphere, offer attractive, competitive, and effective observational capabilities -- namely space-like resolution, transmission, and backgrounds -- that are well suited for modern astronomy and cosmology. SuperBIT is a diffraction-limited, wide-field, 0.5 m telescope capable of exploiting these observing conditions in order to provide exquisite imaging throughout the near-IR to near-UV. It utilizes a robust active stabilization system that has consistently demonstrated a 1 sigma sky-fixed pointing stability at 48 milliarcseconds over multiple 1 hour observations at float. This is achieved by actively tracking compound pendulations via a three-axis gimballed platform, which provides sky-fixed telescope stability at < 500 milliarcseconds and corrects for field rotation, while employing high-bandwidth tip/tilt optics to remove residual disturbances across the science imaging focal plane. SuperBIT's performance during the 2019 commissioning flight benefited from a customized high-fidelity science-capable telescope designed with exceptional thermo- and opto-mechanical stability as well as tightly constrained static and dynamic coupling between high-rate sensors and telescope optics. At the currently demonstrated level of flight performance, SuperBIT capabilities now surpass the science requirements for a wide variety of experiments in cosmology, astrophysics and stellar dynamics.

[14]  arXiv:1911.11222 [pdf, other]
Title: CME Induced Thermodynamic Changes in the Corona as Inferred from Fe XI and Fe XIV Emission Observations during the 2017 August 21 Total Solar Eclipse
Comments: 24 pages, 13 Figures. Accepted for publication in ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present the first remote sensing observations of the impact from a Coronal Mass Ejection (CME) on the thermodynamic properties of the solar corona between 1 and 3 Rs. Measurements of the Fe XI (789.2 nm) and Fe XIV (530.3 nm) emission were acquired with identical narrow-bandpass imagers at three observing sites during the 2017 August 21 Total Solar Eclipse. Additional continuum imagers were used to observe K+F corona scattering, which is critical for the diagnostics presented here. The total distance between sites along the path of totality was 1400 km, corresponding to a difference of 28 minutes between the times of totality at the first and last site. These observations were used to measure the Fe XI and Fe XIV emission relative to continuum scattering, as well as the relative abundance of Fe 10+ and Fe 13+ from the line ratio. The electron temperature (Te) was then computed via theoretical ionization abundance values. We find that the range of Te is 1.1-1.2 x10^6 K in coronal holes and 1.2-1.4 x10^6 K in streamers. Statistically significant changes of Te occurred throughout much of the corona between the sites as a result of serendipitous CME activity prior to the eclipse. These results underscore the unique advantage of multi-site and multi-wavelength total solar eclipse observations for probing the dynamic and thermodynamic properties of the corona over an uninterrupted distance range from 1 to 3 Rs.

[15]  arXiv:1911.11228 [pdf, other]
Title: A LOFAR radio search for single and periodic pulses from M31
Comments: Accepted for publication in A&A. 6 pages with 4 nice figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Bright, short radio bursts are emitted by sources at a large range of distances: from the nearby Crab pulsar to remote Fast Radio Bursts (FRBs). FRBs are likely to originate from distant neutron stars, but our knowledge of the radio pulsar population has been limited to the Galaxy and the Magellanic Clouds. In an attempt to increase our understanding of extragalactic pulsar populations, and its giant-pulse emission, we employed the low-frequency radio telescope LOFAR to search the Andromeda Galaxy (M31) for radio bursts emitted by young, Crab-like pulsars. For direct comparison we also present a LOFAR study on the low-frequency giant pulses from the Crab pulsar; their fluence distribution follows a power law with slope 3.04(3). A number of candidate signals were detected from M31 but none proved persistent. FRBs are sometimes thought of as Crab-like pulsars with exceedingly bright giant pulses -- given our sensitivity, we can rule out that M31 hosts pulsars more than an order of magnitude brighter than the Crab pulsar, assuming their pulse scattering follows that of the known FRBs.

[16]  arXiv:1911.11241 [pdf, other]
Title: High contrast imaging with ELT/METIS: The wind driven halo, from SPHERE to METIS
Comments: AO4ELT6 Conference Proceedings, 12 pages, 8 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

METIS is one of the three first-light instruments planned for the ELT, mainly dedicated to high contrast imaging in the mid-infrared. On the SPHERE high-contrast instrument currently installed at the VLT, we observe that one of the main contrast limitations is the wind driven halo, due to the limited AO running speed with respect to the atmospheric turbulence temporal evolution. From this observation, we extrapolate this signature to the ELT/METIS instrument, which is equipped with a single conjugated adaptive optics system and with several coronagraphic devices. By making use of an analytic AO simulator, we compare the amount of wind driven halo observed with SPHERE and with METIS, under the same turbulence conditions.

[17]  arXiv:1911.11243 [pdf, other]
Title: Enhanced UV radiation and dense clumps in Mrk231's molecular outflow
Comments: Accepted for publication in A&A, 14 pages, 7 figures, 4 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We present interferometric observations of the CN(1-0) line emission in Mrk231 and combine them with previous observations of CO and other H$_2$ gas tracers to study the physical properties of the massive molecular outflow. We find a strong boost of the CN/CO(1-0) line luminosity ratio in the outflow, which is unprecedented compared to any other known Galactic or extragalactic source. For the dense gas phase in the outflow traced by the HCN and CN emissions, we infer $\rm X_{\rm CN}\equiv [CN]/[H_2] > X_{\rm HCN}$ by at least a factor of three, with H$_2$ gas densities of $n_{\rm H_2}\sim10^{5-6}$ cm$^{-3}$. In addition, for the first time, we resolve narrow spectral features in the HCN(1-0) and HCO$^+$(1-0) high-velocity line wings tracing the dense phase of the outflow. The velocity dispersions of these spectral features, $\sigma_v\sim7-20$ km s$^{-1}$, are consistent with those of massive extragalactic giant molecular clouds detected in nearby starburst nuclei. The H$_2$ gas masses inferred from the HCN data are quite high, $M_{mol}\sim0.3-5\times10^8$ $M_{\odot}$. Our results suggest that massive, denser molecular gas complexes survive embedded into the more diffuse H$_2$ phase of the outflow, and that the chemistry of such outflowing dense clouds is affected by enhanced UV radiation.

[18]  arXiv:1911.11273 [pdf, other]
Title: The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet beta Pictoris b from Combined Direct Imaging and Astrometry
Comments: 29 Pages, 23 Figures. Accepted to AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We present new observations of the planet beta Pictoris b from 2018 with GPI, the first GPI observations following conjunction. Based on these new measurements, we perform a joint orbit fit to the available relative astrometry from ground-based imaging, the Hipparcos Intermediate Astrometric Data (IAD), and the Gaia DR2 position, and demonstrate how to incorporate the IAD into direct imaging orbit fits. We find a mass consistent with predictions of hot-start evolutionary models and previous works following similar methods, though with larger uncertainties: 12.8 [+5.3, -3.2] M_Jup. Our eccentricity determination of 0.12 [+0.04, -0.03] disfavors circular orbits. We consider orbit fits to several different imaging datasets, and find generally similar posteriors on the mass for each combination of imaging data. Our analysis underscores the importance of performing joint fits to the absolute and relative astrometry simultaneously, given the strong covariance between orbital elements. Time of conjunction is well constrained within 2.8 days of 2017 September 13, with the star behind the planet's Hill sphere between 2017 April 11 and 2018 February 16 (+/- 18 days). Following the recent radial velocity detection of a second planet in the system, beta Pic c, we perform additional two-planet fits combining relative astrometry, absolute astrometry, and stellar radial velocities. These joint fits find a significantly smaller mass for the imaged planet beta Pic b, of 8.0 +/- 2.6 M_Jup, in a somewhat more circular orbit. We expect future ground-based observations to further constrain the visual orbit and mass of the planet in advance of the release of Gaia DR4.

[19]  arXiv:1911.11275 [pdf, ps, other]
Title: A strange star scenario for the formation of isolated millisecond pulsars
Comments: 9 pages, 11 figures, accepted to publish on A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

According to the recycling model, neutron stars in low-mass X-ray binaries were spun up to millisecond pulsars (MSPs), which indicates that all MSPs in the Galactic plane ought to be harbored in binaries. However, about $20\%$ Galactic field MSPs are found to be solitary. To interpret this problem, we assume that the accreting neutron star in binaries may collapse and become a strange star when it reaches some critical mass limit. Mass loss and a weak kick induced by asymmetric collapse during the phase transition (PT) from neutron star to strange star can result in isolated MSPs. In this work, we use a population-synthesis code to examine the PT model. The simulated results show that a kick velocity of $\sim60~{\rm km~s}^{-1}$ can produce $\sim6\times10^3$ isolated MSPs and birth rate of $\sim6.6\times10^{-7} {\rm ~yr}^{-1}$ in the Galaxy, which is approximately in agreement with predictions from observations. For the purpose of comparisons with future observation, we also give the mass distributions of radio and X-ray binary MSPs, along with the delay time distribution.

[20]  arXiv:1911.11277 [pdf, ps, other]
Title: Identification of Absorption Lines of Heavy Metals in the Wavelength Range 0.97--1.32 Micron
Comments: 19 pages plus 18 pages with additional plots, 5 figures, 3 tables, to be published in the Astrophysical Journal Supplement Series
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Stellar absorption lines of heavy elements can give us various insights into the chemical evolution of the Galaxy and nearby galaxies. Recently developed spectrographs for the near-infrared wavelengths are becoming more and more powerful for producing a large number of high-quality spectra, but identification and characterization of the absorption lines in the infrared range remain to be fulfilled. We searched for lines of the elements heavier than the iron group, i.e., those heavier than Ni, in the Y (9760--11100 AA) and J (11600--13200 AA) bands. We considered the lines in three catalogs, i.e., Vienna Atomic Line Database (VALD), the compilation by R. Kurucz, and the list published in 1999 by Melendez and Barbuy. Candidate lines were selected based on synthetic spectra and the confirmation was done by using WINERED spectra of 13 supergiants and giants within FGK spectral types (spanning 4000--7200 K in the effective temperature). We have detected lines of Zn I, Sr II, Y II, Zr I, Ba II, Sm II, Eu II, and Dy II, in the order of atomic number. Although the number of the lines is small, 23 in total, they are potentially useful diagnostic lines of the Galactic chemical evolution, especially in the regions for which interstellar extinction hampers detailed chemical analyses with spectra in shorter wavelengths. We also report the detection of lines whose presence was not predicted by the synthetic spectra created with the above three line lists.

[21]  arXiv:1911.11282 [pdf, other]
Title: Resolving the FU Ori System with ALMA: Interacting Twin Disks?
Comments: 9 pages, 4 figures, accepted for publication in ApJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

FU Orionis objects are low-mass pre-main sequence stars characterized by dramatic outbursts of several magnitudes in brightness. These outbursts are linked to episodic accretion events in which stars gain a significant portion of their mass. The physical processes behind these accretion events are not yet well understood. The archetypical FU Ori system, FU Orionis, is composed of two young stars with detected gas and dust emission. The continuum emitting regions have not been resolved until now. Here, we present 1.3 mm observations of the FU Ori binary system with ALMA. The disks are resolved at 40 mas resolution. Radiative transfer modeling shows that the emission from FU Ori north (primary) is consistent with a dust disk with a characteristic radius of $\sim$11 au. The ratio between major and minor axes shows that the inclination of the disk is $\sim$37 deg. FU Ori south is consistent with a dust disk of similar inclination and size. Assuming the binary orbit shares the same inclination angle as the disks, the deprojected distance between north and south components is 0.6'', i.e. $\sim$250 au. Maps of $^{12}$CO emission show a complex kinematic environment with signatures disk rotation at the location of the northern component, and also (to a lesser extent) for FU Ori south. The revised disk geometry allows us to update FU Ori accretion models (Zhu et al.), yielding a stellar mass and mass accretion rate of FU Ori north of 0.6 M$_{\odot}$ and 3.8$\times10^{-5}$ M$_{\odot}$ yr$^{-1}$, respectively.

[22]  arXiv:1911.11296 [pdf, ps, other]
Title: Gravitational Waves from Newborn Accreting Millisecond Magnetars
Comments: 8 pages, 3 figures, accepted for publication in PRD
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Two accretion columns have been argued to form over the surface of a newborn millisecond magnetar for an extremely high accretion rate $\gtrsim1.8\times10^{-2}M_\odot\ {\rm s^{-1}}$ that may occur in the core-collapse of a massive star. In this paper, we investigate the characteristics of these accretion columns and their gravitational wave (GW) radiation. For a typical millisecond magnetar (surface magnetic field strength $B\sim10^{15}$ G and initial spin period $P\sim1$ ms), we find (1) its accretion columns are cooled via neutrinos and can reach a height $\sim1$ km over the stellar surface; (2) its column-induced characteristic GW strain is comparable to the sensitivities of the next generation ground-based GW detectors within a horizon $\sim1$ Mpc; (3) the magnetar can survive only a few tens of seconds; (4) during the survival timescale, the height of the accretion columns increases rapidly to the peak and subsequently decreases slowly; (5) the column mass, characteristic GW strain, and maximum GW luminosity have simultaneous peaks in a similar rise-fall evolution. In addition, we find that the magnetar's spin evolution is dominated by the column accretion torque. A possible association with failed supernova is also discussed.

[23]  arXiv:1911.11303 [pdf, other]
Title: Discovery of a Rare Late-Type, Low-Mass Wolf-Rayet Star in the LMC
Comments: Accepted for publication in The Astrophysical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We report the serendipitous discovery of an object, UVQS J060819.93-715737.4, with a spectrum dominated by extremely intense, narrow C II emission lines. The spectrum is similar to those of the very rare, late-type [WC11] low-mass Wolf-Rayet stars. Despite the recognition of these stars as a distinct class decades ago, there remains barely a handful of Galactic members, all of which are also planetary-nebula central stars. Although no obvious surrounding nebulosity is present in J0608, [O II], [N II], and [S II] emission suggest the presence of an inconspicuous, low-excitation nebula. There is low-amplitude incoherent photometric variability on timescales of days to years, as well as numerous prominent P Cygni profiles, implying mass loss. There are indications of a binary companion. The star is located on the outskirts of the LMC, and the observed radial velocity (~250 km/s) and proper motion strongly suggest membership. If indeed an LMC member, this is the first extragalactic late [WC] star, and the first with an accurately determined luminosity, as the Galactic examples are too distant for precise parallax determinations. A high-quality, broad-coverage spectrum of the prototype of the late [WC] class, CPD -56 8032, is also presented. We discuss different excitation mechanisms capable of producing the great strength of the C II emission. Numerous autoionizing levels of C II are definitely populated by processes other than dielectronic recombination. Despite the spectacular emission spectra, observational selection makes objects such as these difficult to discover. Members of the [WC11] class may in fact be considerably more common than the handful of previously known late [WC] stars.

[24]  arXiv:1911.11325 [pdf, other]
Title: Kinematical Investigation of Possible Fast Collimated Outflows in Twelve Planetary Nebulae
Comments: 14 pages, 12 figures, ACCEPTED
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

A significant fraction of planetary nebulae (PNe) exhibit collimated outflows, distinct narrow kinematical components with notable velocity shifts with respect to the main nebular shells typically associated with low-ionization compact knots and linear or precessing jet-like features. We present here a spatio-kinematical investigation of a sample of twelve PNe with morphologies in emission lines of low-ionization species suggestive of collimated outflows. Using archival narrow-band images and our own high-dispersion long-slit echelle spectra, we confirm the presence of collimated outflows in Hen 2-429, J 320, M 1-66, M 2-40, M 3-1, and NGC 6210 and possibly in NGC 6741, for which the spatio-kinematical data can also be interpreted as a pair of bipolar lobes. The presence of collimated outflows is rejected in Hen 2-47, Hen 2-115, M 1-26, and M 1-37, but their morphology and kinematics are indicative of the action of supersonic outflows that have not been able to pierce through the nebular envelope. In this sense, M 1-66 appears to have experienced a similar interaction between the outflow and nebular envelope, but, as opposed to these four PNe, the outflow has been able to break through the nebular envelope. It is suggested that the PNe without collimated outflows in our sample are younger or descend from lower mass progenitors than those that exhibit unambiguous collimated outflows.

[25]  arXiv:1911.11349 [pdf, other]
Title: CMB B-mode non-Gaussianity: optimal bispectrum estimator and Fisher forecasts
Comments: 40 pages, 7 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Upcoming cosmic microwave background (CMB) data can be used to explore harmonic 3-point functions that involve the B-mode component of the CMB polarization signal. We focus on bispectra describing the non-Gaussian correlation of the B-mode field and the CMB temperature anisotropies (T) and/or E-mode polarization, i.e. <TTB>, <EEB>, and <TEB>. Such bispectra probe violations of the tensor consistency relation: the model-independent behavior of cosmological correlation functions that involve a large-wavelength tensor mode (gravitational wave). An observed violation of the tensor consistency relation would exclude a large number of inflation models. We describe a generalization of the Komatsu-Spergel-Wandelt (KSW) bispectrum estimator that allows statistical inference on this type of primordial non-Gaussianity with data of the CMB temperature and polarization anisotropies. The generalized estimator shares its statistical properties with the existing KSW estimator and retains the favorable numerical scaling with angular resolution. In this paper we derive the estimator and present a set of Fisher forecasts. We show how the forecasts scale with various experimental parameters such as lower and upper angular band-limit, relevant for e.g. the upcoming ground-based Simons Observatory experiment and proposed LiteBIRD satellite experiment. We comment on possible contaminants due to secondary cosmological and astrophysical sources.

[26]  arXiv:1911.11364 [pdf, other]
Title: Multiwavelength Polarimetry of the Filamentary Cloud IC5146: II. Magnetic Field Structures
Comments: 25 pages, 22 figures, accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The IC5146 cloud is a nearby star-forming region in Cygnus, consisting of molecular gas filaments in a variety of evolutionary stages. We used optical and near-infrared polarization data toward the IC5146 cloud, reported in the first paper of this series, to reveal the magnetic fields in this cloud. Using the newly released $Gaia$ data, we found that the IC5146 cloud may contain two separate clouds: a first cloud, including the densest main filament at a distance of $\sim$600 pc, and a second cloud, associated with the Cocoon Nebula at a distance of $\sim$800 pc. The spatially averaged H-band polarization map revealed a well-ordered magnetic field morphology, with the polarization segments perpendicular to the main filament but parallel to the nearby sub-filaments, consistent with models assuming that the magnetic field is regulating cloud evolution. We estimated the magnetic field strength using the Davis-Chandrasekhar-Fermi method, and found that the magnetic field strength scales with volume density with a power-law index of $\sim0.5$ in the density range from $N_{H_2}\sim$ 10 to 3000 cm$^{-3}$, which indicates an anisotropic cloud contraction with a preferred direction along the magnetic field. In addition, the mass-to-flux ratio of the cloud gradually changes from subcritical to supercritical from the cloud envelope to the deep regions. These features are consistent with strong magnetic field star-formation models and suggest that the magnetic field is important in regulating the evolution of the IC5146 cloud.

[27]  arXiv:1911.11399 [pdf, ps, other]
Title: The clockwork is moving on -- a combined analysis of TESS and Kepler measurements of Kepler-13Ab
Comments: 5 pages, 4 figures, 1 table; accepted by MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Kepler-13Ab (KOI-13) is an exoplanet orbiting a rapidly rotating A-type star. The system shows a significant spin-orbit misalignment and a changing transit duration most probably caused by the precession of the orbit. Here we present a self-consistent analysis of the system combining {\it Kepler} and TESS observations. We model the light curves asssuming a planet transits a rotating oblate star which has a strong surface temperature gradient due to rotation-induced gravity darkening. The transit chord moves slowly as an emergent feature of orbital precession excited by the oblate star with a decline rate in the impact parameter of ${\rm d}b/{\rm d}t = -0.011/{\rm yr}$, and with an actual value of $b=0.19$ for the latest TESS measurements. The changing transit duration that was measured from {\it Kepler} Q2 and Q17 quarters and the TESS measurements indicates a linear drift of the impact parameter. The solutions for the stellar spin axis suggest a nearly orthogonal aspect, with inclination around $100^\circ$.

[28]  arXiv:1911.11442 [pdf, ps, other]
Title: A New Probe of Gaussianity and Isotropy for CMB Maps
Comments: 13 pages, 25 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We introduce a new mathematical tool (a direction-dependent probe) to analyse the randomness of purported isotropic Gaussian random fields on the sphere. We apply the probe to assess the full-sky cosmic microwave background (CMB) temperature maps produced by the {\it Planck} collaboration (PR2 2015 and PR3 2018), with special attention to the inpainted maps. To study the randomness of the fields represented by each map we use the autocorrelation of the sequence of probe coefficients (which are just the full-sky Fourier coefficients $a_{\ell,0}$ if the $z$ axis is taken in the probe direction). If the field is {isotropic and Gaussian} then the probe coefficients for a given direction should be realisations of uncorrelated scalar Gaussian random variables. We find that for most of the maps there are many directions for which this is not the case. We make a first attempt at justifying the features of the temperature maps that contribute to the apparent lack of randomness. In the case of \texttt{Commander} 2015 we mimic an aspect of the observed behaviour with a model field that is Gaussian but not isotropic. In contrast, the non-inpainted 2018 \texttt{SEVEM} map (which has visible equatorial pollution) is modelled by an isotropic Gaussian random field plus a non-random needlet-like structure located near the galactic centre.

[29]  arXiv:1911.11447 [pdf, other]
Title: Dense Cores, Filaments and Outflows in the S255IR Region of High Mass Star Formation
Authors: Igor I. Zinchenko (1), Sheng-Yuan Liu (2), Yu-Nung Su (2), Kuo-Song Wang (2), Yuan Wang (3) ((1) Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, Russia, (2) Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan, R.O.C., (3) Max-Planck-Institut fuer Astronomie, Heidelberg, Germany)
Comments: 15 pages, 14 figures, accepted by the Astrophysical Journal
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We investigate at a high angular resolution the spatial and kinematic structure of the S255IR high mass star-forming region, which demonstrated recently the first disk-mediated accretion burst in the massive young stellar object. The observations were performed with ALMA in Band 7 at an angular resolution $ \sim 0.1^{\prime\prime}$, which corresponds to $ \sim 180 $ AU. The 0.9 mm continuum, C$^{34}$S(7-6) and CCH $N=4-3$ data show a presence of very narrow ($ \sim 1000 $ AU), very dense ($n\sim 10^7$ cm$^{-3}$) and warm filamentary structures in this area. At least some of them represent apparently dense walls around the high velocity molecular outflow with a wide opening angle from the S255IR-SMA1 core, which is associated with the NIRS3 YSO. This wide-angle outflow surrounds a narrow jet. At the ends of the molecular outflow there are shocks, traced in the SiO(8-7) emission. The SiO abundance there is enhanced by at least 3 orders of magnitude. The CO(3-2) and SiO(8-7) data show a collimated and extended high velocity outflow from another dense core in this area, SMA2. The outflow is bent and consists of a chain of knots, which may indicate periodic ejections possibly arising from a binary system consisting of low or intermediate mass protostars. The C$^{34}$S emission shows evidence of rotation of the parent core. Finally, we detected two new low mass compact cores in this area (designated as SMM1 and SMM2), which may represent prestellar objects.

[30]  arXiv:1911.11450 [pdf, other]
Title: Expanding Core-Collapse Supernova Search Horizon of Neutrino Detectors
Comments: 4 pages, 2 figures, this contribution was accepted by IOP Conference Series - proceedings services for science
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Experiment (hep-ex); Data Analysis, Statistics and Probability (physics.data-an)

Core-Collapse Supernovae, failed supernovae and quark novae are expected to release an energy of few $10^{53}$ ergs through MeV neutrinos and a network of detectors is operative to look online for these events. However, when the source distance increases and/or the average energy of emitted neutrinos decreases, the signal statistics drops and the identification of these low statistic astrophysical bursts could be challenging. In a standard search, neutrino detectors characterise the observed clusters of events with a parameter called multiplicity, i.e. the number of collected events in a fixed time-window. We discuss a new parameter called $\xi$ (=multiplicity/duration of the cluster) in order to add the information on the temporal behaviour of the expected signal with respect to background. By adding this parameter to the multiplicity we optimise the search of astrophysical bursts and we increase their detection horizon. Moreover, the use of the $\xi$ can be easily implemented in an online system and can apply also to a network of detectors like SNEWS. For these reasons this work is relevant in the multi-messengers era when fast alerts with high significance are mandatory.

[31]  arXiv:1911.11478 [pdf, other]
Title: Compact Groups of Galaxies in Sloan Digital Sky Survey and LAMOST Spectral Survey: I. The Catalogues
Comments: 22 pages, 9 figures, 8 tables, Full catalogues will be available when the paper is accepted
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Compact group (CG) is a kind of special galaxy system where the galaxy members are separated at the distances of the order of galaxy size. The strong interaction between the galaxy members makes CGs ideal labs for studying the environmental effects on galaxy evolution. Traditional photometric selection algorithm biases against the CG candidates at low redshifts, while spectroscopic identification technique is affected by the spectroscopic incompleteness of sample galaxies and typically biases against the high redshift candidates. In this study, we combine these two methods and select CGs in the main galaxy sample of the Sloan Digital Sky Survey, where we also have taken the advantages of the complementary redshift measurements from the LAMOST spectral and GAMA surveys. We have obtained the largest and most complete CG samples to date. Our samples include 6,144 CGs and 8,022 CG candidates, which are unique in the studies of the nature of the CGs and the evolution of the galaxies inside.

[32]  arXiv:1911.11480 [pdf, other]
Title: Mass Bias of Weak Lensing Shear-selected Galaxy Cluster Samples
Comments: Submitted to ApJ; 15 pages, 10 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We estimate the bias on weak lensing mass measurements of shear-selected galaxy cluster samples. The mass bias is expected to be significant because constructions of cluster samples from peaks in weak lensing mass maps and measurements of cluster masses from their tangential shear profiles share the same noise. We quantify this mass bias from large sets of mock cluster samples with analytical density profiles and realistic large-scale structure noise from ray-tracing simulations. We find that, even for peaks with signal-to-noise ratio larger than $4.0$ in weak lensing mass maps constructed in a deep survey with a high source galaxy number density of $30~\mathrm{arcmin}^{-2}$, derived weak lensing masses for these shear-selected clusters are still biased high by $\sim55\%$ on average. Such a large bias mainly originates from up-scattered low mass objects, which is an inevitable consequence of selecting clusters with a noisy observable directly linked to the mass measurement. We also investigate the dependence of the mass bias on different physical and observational parameters, finding that the mass bias strongly correlates with cluster redshifts, true halo masses, and selection signal-to-noise thresholds, but having moderate dependence on observed weak lensing masses and survey depths. This bias, albeit considerable, can still be modeled accurately in statistical studies of shear-selected clusters as the intrinsic scatter around the mean bias is found to be reasonable in size. We demonstrate that such a bias can explain the deviation in X-ray properties previously found on a shear-selected cluster sample. Our result will be useful for turning large samples of shear-selected clusters available in future surveys into potential probes of cosmology and cluster astrophysics.

[33]  arXiv:1911.11491 [pdf, other]
Title: Testing the robustness of black hole mass measurements with ALMA and MUSE
Comments: 5 pages, 3 figures, Proceeding of IAU Symposium 353, Galactic Dynamics in the Era of Large Surveys, ed. M. Valluri & J. A. Sellwood, Cambridge Univ. Press, in press; submitted September, 2019
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present our ongoing work of using two independent tracers to estimate the supermassive black hole mass in the nearby early-type galaxy NGC 6958; namely integrated stellar and molecular gas kinematics. We used data from the Atacama Large Millimeter/submillimeter Array (ALMA), and the adaptive-optics assisted Multi-Unit Spectroscopic Explorer (MUSE) and constructed state-of-the-art dynamical models. The different methods provide black hole masses of $(2.89\pm 2.05) \times 10^8M_{\odot}$ from stellar kinematics and $(1.35\pm 0.09) \times 10^8M_{\odot}$ from molecular gas kinematics which are consistent within their $3\sigma$ uncertainties. Compared to recent M$_{\rm BH}$ - $\sigma_{\rm e}$ scaling relations, we derive a slightly over-massive black hole. Our results also confirm previous findings that gas-based methods tend to provide lower black hole masses than stellar-based methods. More black hole mass measurements and an extensive analysis of the method-dependent systematics are needed in the future to understand this noticeable discrepancy.

[34]  arXiv:1911.11497 [pdf, other]
Title: Gaussian processes reconstruction of modified gravitational wave propagation
Comments: 16 pages, 26 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Recent work has shown that modified gravitational wave (GW) propagation can be a powerful probe of dark energy and modified gravity, specific to GW observations. We use the technique of Gaussian processes, that allows the reconstruction of a function from the data without assuming any parametrization, to measurements of the GW luminosity distance from simulated joint GW-GRB detections, combined with measurements of the electromagnetic luminosity distance by simulated DES data. For the GW events we consider both a second-generation LIGO/Virgo/Kagra (HVLKI) network, and a third-generation detector such as the Einstein Telescope. We find that the HVLKI network at target sensitivity, with $O(15)$ neutron star binaries with electromagnetic counterpart, could already detect deviations from GR at a level predicted by some modified gravity models, and a third-generation detector such as ET would have a remarkable discovery potential. We discuss the complementarity of the Gaussian processes technique to the $(\Xi_0,n)$ parametrization of modified GW propagation.

[35]  arXiv:1911.11498 [pdf, other]
Title: Collapse of spherical overdensities in superfluid models of dark matter
Comments: 10 pages, 9 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We intend to understand cosmological structure formation within the framework of superfluid models of dark matter with finite temperatures. Of particular interest is the evolution of small-scale structures where the pressure and superfluid properties of the dark matter fluid are prominent. We compare the growth of structures in the superfluid dark matter with that of the standard cold dark matter paradigm and non-superfluid dark matter. The equations for superfluid hydrodynamics are computed numerically in an expanding $\Lambda$CDM background with spherical symmetry, and the effect of various superfluid fractions, temperatures, interactions, and masses on the collapse of structures is considered. The linear perturbation of the superfluid equations is derived, which gives further insight of the dynamics of the superfluid dark matter collapse. It is found that while a conventional dark matter fluid with self-interactions and finite temperatures experiences a suppression in the growth of structures at smaller scales, as expected due to the presence of pressure terms, a superfluid can collapse much more efficiently due to its ability to suppress the growth of entropy perturbations and thus gradients in the thermal pressure. It is also found that the cores of the dark matter halos initially become more superfluid during the collapse, but eventually reach a point where the superfluid fraction falls sharply. The formation of superfluid dark matter halos surrounded by a normal fluid dark matter background is therefore disfavored by the present work.

[36]  arXiv:1911.11526 [pdf, other]
Title: Accelerated orbital decay of supermassive black hole binaries in merging nuclear star clusters
Comments: 13 pages, 8 figures, 2 tables and appendices, submitted to MNRAS on 2019 Oct. 18
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The coalescence of supermassive black holes (SMBHs) should generate the strongest sources of gravitational waves (GWs) in the Universe. However, the dynamics of their coalescence is the subject of much debate. In this study, we use a suite of $N$-body simulations to follow the merger of two nuclear star clusters (NSCs), each hosting a SMBH in their centre. We find that the presence of distinct star clusters around each SMBH has important consequences for the dynamical evolution of the SMBH binary: (i) The separation between the SMBHs decreases by a few orders of magnitude in the first few Myrs by the combined effects of dynamical friction and a drag force caused by tidally stripped stars. In fact, this is a significant speedup for equal mass ratio binaries, and becomes extreme for unequal mass ratios, e.g. 1:10 or 1:100, which traditional dynamical friction alone would not permit to bind. (ii) The subsequent binary hardening is driven by the gravitational slingshots between the SMBH binary and stars, and also depends on the mass ratio between the SMBHs. Thus, with this additional drag force, we find that all SMBHs in our suite coalesce within a Hubble time. Given that about 50% of Milky Way sized galaxies host NSCs, our results are encouraging for upcoming GW observations with the Laser Interferometer Space Antenna -- LISA -- which will detect SMBH coalescence in the $10^4-10^7$$M_{\rm \odot}$ mass range.

[37]  arXiv:1911.11545 [pdf, other]
Title: The Forgotten Quadrant Survey. $^{12}$CO and $^{13}$CO (1-0) survey of the Galactic Plane in the range 220°$<l<$240° -2.5°$<b<$0°
Comments: 16 pages, 17 figures, accepted for publication in Astronomy and Astrophysics
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the Forgotten Quadrant Survey (FQS), an ESO large project that used the 12m antenna of the Arizona Radio Observatory to map the Galactic Plane in the range 220\deg$<l<$240\deg and -2.5\deg$<b<$0\deg, both in $^{12}$CO(1-0) and $^{13}$CO(1-0), at a spectral resolution of 0.65 km s$^{-1}$ and 0.26 km s$^{-1}$. Our dataset allows us to easily identify how the molecular dense gas is organised at different spatial scales: from the giant clouds with their denser filamentary networks, down to the clumps and cores that host the newborn stars and to obtain reliable estimates of their key physical parameters. We present the first release of the FQS data and discuss their quality. Spectra with 0.65 km s$^{-1}$ velocity channels have a noise ranging from 0.8 K to 1.3 K for $^{12}$CO(1-0) and from 0.3 K to 0.6 K for $^{13}$CO(1-0). In this paper, we used the $^{12}$CO(1-0) spectral cubes to produce a catalogue of 263 molecular clouds. This is the first selfconsistent, statistical catalogue of molecular clouds of the outer Galaxy, obtained with a subarcminute spatial resolution and therefore able to detect not only the classical giant molecular clouds, but also the small clouds and to resolve the cloud structure at the subparsec scale up to a distance of a few kpc. We found two classes of objects: structures with size above a few parsecs that are typical molecular clouds and may be self-gravitating, and subparsec structures that cannot be in gravitational equilibrium and are likely transient or confined by external pressure. We used the ratio between the Herschel H$_2$ column density and the integrated intensity of the CO lines to calculate the CO conversion factor and we found mean values of (3.3$\pm$1.4)$\times 10^{20}$ cm$^{-2}$(K km s$^{-1})^{-1}$ and (1.2$\pm$0.4)$\times 10^{21}$ cm$^{-2}$(K km s$^{-1})^{-1}$, for $^{12}$CO(1-0) and $^{13}$CO(1-0), respectively.

[38]  arXiv:1911.11570 [pdf, other]
Title: Magnetic energy dissipation and origin of non-thermal spectra in radiatively efficient relativistic sources
Comments: accepted for publication by MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The dissipation of turbulent magnetic fields is an appealing scenario to explain the origin of non-thermal particles in high-energy astrophysical sources. However, it has been suggested that the particle distribution may effectively thermalise when the radiative (synchrotron and/or Inverse Compton) losses are severe. Inspired by recent PIC simulations of relativistic turbulence, which show that electrons are impulsively heated in intermittent current sheets by a strong electric field aligned with the local magnetic field, we instead argue that in plasmas where the particle number density is dominated by the pairs (electron-positron and electron-positron-ion plasmas): (i) as an effect of fast cooling and of different injection times, the electron energy distribution is ${\rm d}n_e/{\rm d}\gamma\propto\gamma^{-2}$ for $\gamma\lesssim\gamma_{\rm heat}$ (the Lorentz factor $\gamma_{\rm heat}$ being close to the equipartition value), while the distribution steepens at higher energies; (ii) since the time scales for the turbulent fields to decay and for the photons to escape are of the same order, the magnetic and the radiation energy densities in the dissipation region are comparable; (iii) if the mass energy of the plasma is dominated by the ion component, the pairs with a Lorentz factor smaller than a critical one (of the order of the proton-to-electron mass ratio) become isotropic, while the pitch angle remains small otherwise. The outlined scenario is consistent with the typical conditions required to reproduce the Spectral Energy Distribution of blazars, and allows one to estimate the magnetisation of the emission site. Finally, we show that turbulence within the Crab Nebula may power the observed gamma-ray flares if the pulsar wind is nearly charge-separated at high latitudes.

[39]  arXiv:1911.11572 [pdf]
Title: Laser-Driven High-Velocity Microparticle Launcher In Atmosphere And Under Vacuum
Comments: 13 pages, 9 figures, keywords: high-velocity launcher; microparticle impact; high-speed imaging; low vacuum; laser-based method; table-top system; ejecta; drag; blast; ballistic limit
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Materials Science (cond-mat.mtrl-sci); Applied Physics (physics.app-ph); Optics (physics.optics)

This paper presents a novel approach to launch single microparticles at high velocities under low vacuum conditions. In an all-optical table-top method, microparticles with sizes ranging from a few microns to tens of microns are accelerated to supersonic velocities depending on the particle mass. The acceleration is performed through a laser ablation process and the particles are monitored in free space using an ultra-high-speed multi-frame camera with nanosecond time resolution. Under low vacuum, we evaluate the current platform performance by measuring particle velocities for a range of particle types and sizes, and demonstrate blast wave suppression and drag reduction under vacuum. Showing an impact on polyethylene, we demonstrate the capability of the experimental setup to study materials behavior under high-velocity impact. The present method is relevant to space applications, particularly to rendezvous missions where velocities range from tens of m/s to a few km/s, as well as to a wide range of terrestrial applications including impact bonding and impact-induced erosion.

[40]  arXiv:1911.11579 [pdf, other]
Title: The Huntsman Telescope
Comments: 7 pages, 4 figures, Conference proceeding for the IAU Symposium 355 "The Realm of the Low Surface Brightness Universe" held July 8-12, 2019
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)

The Huntsman Telescope, located at Siding Spring Observatory in Australia, is a system of ten telephoto Canon lenses designed for low surface brightness imaging in the Southern sky. Based upon the Dragonfly Telephoto Array, the refractive lens-based system provides an obstruction free optical path, which reduces the number of scattering surfaces and allows easier access to lower surface brightness levels.
In this proceeding, we present an analysis of the impact of flat fielding uncertainty on the limiting low surface brightness levels. We show that a fairly standard set of flat-field data can be well-characterised to a $\sim0.1\%$ level. This corresponds to a 5-$\sigma$ lower limit of $\sim33$ magnitude per arcsecond$^2$, which means that flat fielding is not likely going to set Huntsman's low surface brightness limit.
We also present early results of an exoplanet transient mode for Huntsman where all lenses work together to detect subtle variations in the luminosity of relatively bright $V=8-12$ magnitude stars. High-precision exoplanet imaging is ultimately limited by systematic uncertainties, so we anticipate multiple lenses will help to mitigate issues related to pixel-to-pixel and intra-pixel sensitivity variations. Our initial results show we can easily get $\sim0.4\%$ photometric precision with a single, defocused lens.

[41]  arXiv:1911.11586 [pdf, ps, other]
Title: Cascade disruptions in asteroid clusters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We studied asteroid clusters suggesting a possibility of at least two disruption events in their recent history (< 5 Myr). We searched for new members of known asteroid pairs and clusters and we verified their membership. We found four asteroid clusters, namely the clusters of (11842) Kap'bos, (14627) Emilkowalski, (63440) 2001 MD30 and (157123) 2004 NW5 that show at least two secondary separation events that occurred at significantly different times. We considered a possible formation mechanism for these clusters: The parent of an asteroid cluster was spun up to its critical rotation frequency, underwent a rotation fission and was slowed down by escape of the newly formed secondary/ies. Then the YORP effect spun up the primary again and it reached its critical rotation frequency and underwent another fission. We created a simple model to test whether this scenario is possible for the four clusters. We obtained a good agreement between the model and the cluster properties for the clusters of Kap'bos and (63440). For the cluster of Emilkowalski, the time needed for the primary to reach its critical frequency after the first fission event was predicted to be too long by a factor of several. We suspect, considering also its D type taxonomic classification and the existence of a dust band associated with the cluster, that the asteroid Emilkowalski may actually be a cometary nucleus. For the cluster of (157123), the final rotational frequency of the primary after the last fission event predicted by our model is in a good agreement with the observed rotation frequency of (157123). However, a separation of the older secondary is not possible in our model due to the deficiency of free energy needed for an escape of the large secondary. This could be due to an error in the H value of the secondary or the possibility that we did not find the real primary of this cluster.

[42]  arXiv:1911.11588 [pdf, other]
Title: The Diffuse Ionized Gas Halo of the Small Magellanic Cloud
Comments: 16 pages, 8 figures, 3 tables
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Observations with the Wisconsin H-alpha Mapper (WHAM) reveal a large, diffuse ionized halo that surrounds the Small Magellanic Cloud (SMC). We present the first kinematic H-alpha survey of an extended region around the galaxy, from (l,b) = (289.5,-35.0) to (315.1,-5.3) and covering +90 <= vLSR <= +210 km s-1. The ionized gas emission extends far beyond the central stellar component of the galaxy, reaching similar distances to that of the diffuse neutral halo traced by 21 cm observations. H-alpha emission extends several degrees beyond the sensitivity of current H I surveys toward smaller Galactic longitudes and more negative Galactic latitudes. The velocity field of the ionized gas near the SMC appears similar to to the neutral halo of the galaxy. Using the observed emission measure as a guide, we estimate the mass of this newly revealed ionized component to be roughly (0.8 - 1.0) x 10^9 M_sun, which is comparable to the total neutral mass in the same region of (0.9 - 1.1) x 10^9 M_sun. We find ratios of the total ionized gas mass divided by the total neutral plus ionized gas mass in three distinct subregions to be: (1) 46%-54% throughout the SMC and its extended halo, (2) 12%-32% in the SMC Tail that extends toward the Magellanic Bridge, and (3) 65%-79% in a filament that extends away from the SMC toward the Magellanic Stream. This newly discovered, coherent H-alpha filament does not appear to have a well-structured neutral component and is also not coincident with two previously identified filaments traced by 21 cm emission within the Stream.

[43]  arXiv:1911.11647 [pdf, other]
Title: ALMA and ROSINA detections of phosphorus-bearing molecules: the interstellar thread between star-forming regions and comets
Comments: Accepted in MNRAS (20 pages, 12 figures)
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

To understand how Phosphorus-bearing molecules are formed in star-forming regions, we have analysed ALMA observations of PN and PO towards the massive star-forming region AFGL 5142, combined with a new analysis of the data of the comet 67P/Churyumov-Gerasimenko taken with the ROSINA instrument onboard Rosetta. The ALMA maps show that the emission of PN and PO arises from several spots associated with low-velocity gas with narrow linewidths in the cavity walls of a bipolar outflow. PO is more abundant than PN in most of the spots, with the PO/PN ratio increasing as a function of the distance to the protostar. Our data favor a formation scenario in which shocks sputter phosphorus from the surface of dust grains, and gas-phase photochemistry induced by UV photons from the protostar allows efficient formation of the two species in the cavity walls. Our analysis of the ROSINA data has revealed that PO is the main carrier of P in the comet, with PO/PN>10. Since comets may have delivered a significant amount of prebiotic material to the early Earth, this finding suggests that PO could contribute significantly to the phosphorus reservoir during the dawn of our planet. There is evidence that PO was already in the cometary ices prior to the birth of the Sun, so the chemical budget of the comet might be inherited from the natal environment of the Solar System, which is thought to be a stellar cluster including also massive stars.

[44]  arXiv:1911.11683 [pdf, ps, other]
Title: Direct effects of the environment on AGN triggering in SDSS spiral galaxies: merger-AGN connection
Comments: 13 pages, 8 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We examine whether galaxy environments directly affect triggering nuclear activity in Sloan Digital Sky Survey (SDSS) local spiral galaxies using a volume-limited sample with the $r$-band absolute magnitude $M_{r} < -19.0$ and $0.02 < z < 0.055$ selected from the SDSS Data Release 7. To avoid incompleteness of the central velocity dispersion $\sigma$ of the volume-limited sample and to fix the black hole mass affecting AGN activity, we limit the sample to a narrow $\sigma$ range of $130$ km s$^{-1}<\sigma<200$ km s$^{-1}$. We define a variety of environments as a combination of neighbour interactions and local density on a galaxy. After the central star formation rate (which is closely related to AGN activity level) is additionally restricted, the direct impact of the environment is unveiled. In the outskirts of rich clusters, red spiral galaxies show a significant excess of the AGN fraction despite the lack of central gas. We argue that they have been pre-processed before entering the rich clusters, and due to mergers or strong encounters in the in-fall region, their remaining gases efficiently lose angular momentum. We investigate an environment in which many star-forming galaxies coexist with a few starburst-AGN composite hosts having the highest [OIII] luminosity. We claim that they are a gas-rich merger product in groups or are group galaxies in-falling into clusters, indicating that many AGN signatures may be obscured following the merger events.

[45]  arXiv:1911.11684 [pdf, ps, other]
Title: Collisional Ionization in the X-ray Spectrum of the Ultracompact Binary 4U 1626-67
Comments: 23 pages, 13 figures. Submitted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

We report on high-resolution X-ray spectroscopy of the ultracompact X-ray binary pulsar 4U 1626-67 with Chandra/HETGS acquired in 2010, two years after the pulsar experienced a torque reversal. The well-known strong Ne and O emission lines with Keplerian profiles are shown to arise at the inner edge of the magnetically-channeled accretion disk. We exclude a photoionization model for these lines based on the absence of sharp radiative recombination continua. Instead, we show that the lines arise from a collisional plasma in the inner-disk atmosphere, with $T\simeq 10^7$ K and $n_e \sim 10^{17}$ cm^(-3). We suggest that the lines are powered by X-ray heating of the optically-thick disk inner edge at normal incidence. Comparison of the line profiles in HETGS observations from 2000, 2003, and 2010 show that the inner disk radius decreased by a factor of two after the pulsar went from spin-down to spin-up, as predicted by magnetic accretion torque theory. The inner disk is well inside the corotation radius during spin-up, and slightly beyond the corotation radius during spin-down. Based on the disk radius and accretion torque measured during steady spin-up, the pulsar's X-ray luminosity is $2\times 10^{36}$ erg/s, yielding a source distance of 3.5(+0.2-0.3) kpc. The mass accretion rate is an order of magnitude larger than expected from gravitational radiation reaction, possibly due to X-ray heating of the donor. The line profiles also indicate a binary inclination of 39(+20-10) degrees, consistent with a 0.02 Msun donor star. Our emission measure analysis favors a He white dwarf or a highly-evolved H-poor main sequence remnant for the donor star, rather than a C-O or O-Ne white dwarf. The measured Ne/O ratio is 0.46+-0.14 by number. In an appendix, we show how to express the emission measure of a H-depleted collisional plasma without reference to a H number density.

[46]  arXiv:1911.11687 [pdf, other]
Title: The Design of The CCAT-prime Epoch of Reionization Spectrometer Instrument
Comments: 10 pages, 5 figures, 18th International Workshop on Low Temperature Detectors, submitted to the Journal of Low Temperature Physics
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The Epoch of Reionization Spectrometer (EoR-Spec) is an instrument module for the Prime-Cam receiver of the 6 m aperture CCAT-prime Telescope at 5600 m in Chile. EoR-Spec will perform 158 $\mu$m [CII] line intensity mapping of star-forming regions at redshifts between 3.5 and 8 (420 - 210 GHz), tracing the evolution of structure during early galaxy formation. At lower redshifts, EoR-Spec will observe galaxies near the period of peak star formation - when most stars in today's universe were formed. At higher redshifts, EoR-Spec will trace the late stages of reionization, the early stages of galaxy assembly, and the formation of large-scale, three-dimensional clustering of star-forming galaxies. To achieve its science goals, EoR-Spec will utilize CCAT-prime's exceptionally low water vapor site, large field of view ($\sim 5$ degrees at 210 GHz), and narrow beam widths ($\sim 1$ arcminute at 210 GHz). EoR-Spec will be outfitted with a cryogenic, metamaterial, silicon substrate-based Fabry-Perot Interferometer operating at a resolving power ($\lambda/\Delta\lambda$) of 100. Monolithic dichroic arrays of cryogenic, feedhorn-coupled transition edge sensor bolometers provide approximately 6000 detectors, which are read out using a frequency division multiplexing system based on microwave SQUIDs. The novel design allows the measurement of the [CII] line at two redshifts simultaneously using dichroic pixels and two orders of the Fabry-Perot. Here we present the design and science goals of EoR-Spec, with emphasis on the spectrometer, detector array, and readout designs.

[47]  arXiv:1911.11701 [pdf, other]
Title: Shot noise in multi-tracer constraints on $f_\text{NL}$ and relativistic projections: Power Spectrum
Comments: Comments are welcomed
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Multiple tracers of the same surveyed volume can enhance the signal-to-noise on a measurement of local primordial non-Gaussianity and the relativistic projections. Increasing the number of tracers comparably increases the number of shot noise terms required to describe the stochasticity of the data. Although the shot noise is white on large scales, it is desirable to investigate the extent to which it can degrade constraints on the parameters of interest. In a multi-tracer analysis of the power spectrum, a marginalization over shot noise does not degrade the constraints on $f_\text{NL}$ by more than $\sim 30$% so long as halos of mass $M\lesssim 10^{12}M_\odot$ are resolved. However, ignoring cross shot noise terms induces large systematics on a measurement of $f_\text{NL}$ at redshift $z<1$ when small mass halos are resolved. These effects are less severe for the relativistic projections, especially for the dipole term. In the case of a low and high mass tracer, the optimal sample division maximizes the signal-to-noise on $f_\text{NL}$ and the projection effects simultaneously, reducing the errors to the level of $\sim 10$ consecutive mass bins of equal number density. We also emphasize that the non-Poissonian noise corrections that arise from small-scale clustering effects cannot be measured with random dilutions of the data. Therefore, they must either be properly modeled or marginalized over.

[48]  arXiv:1911.11710 [pdf, ps, other]
Title: 2SXPS: An improved and expanded Swift X-ray telescope point source catalog
Comments: Submitted to ApJS, 20 pages, 6 figures, plus appendices of 17 pages, 3 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

We present the 2SXPS (Swift-XRT Point Source) catalog, containing 206,335 point sources detected by the Swift X-ray Telescope (XRT) in the 0.3--10 keV energy range. This catalog represents a significant improvement over 1SXPS, with double the sky coverage (now 3,790 deg$^2$), and several significant developments in source detection and classification. In particular, we present for the first time techniques to model the effect of stray light -- significantly reducing the number of spurious sources detected. These techniques will be very important for future, large effective area X-ray mission such as the forthcoming Athena X-ray observatory. We also present a new model of the XRT point spread function, and a method for correctly localising and characterising piled up sources. We provide light curves -- in four energy bands, two hardness ratios and two binning timescales -- for every source, and from these deduce that over 80,000 of the sources in 2SXPS are variable in at least one band or hardness ratio. The catalog data can be queried or downloaded via a bespoke web interface at https://www.swift.ac.uk/2SXPS, via HEASARC, or in Vizier (IX/58).

[49]  arXiv:1911.11714 [pdf, other]
Title: Decoding the radial velocity variations of HD41248 with ESPRESSO
Comments: Accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Twenty-four years after the discoveries of the first exoplanets, the radial-velocity (RV) method is still one of the most productive techniques to detect and confirm exoplanets. But stellar magnetic activity can induce RV variations large enough to make it difficult to disentangle planet signals from the stellar noise. In this context, HD41248 is an interesting planet-host candidate, with RV observations plagued by activity-induced signals. We report on ESPRESSO observations of HD41248 and analyse them together with previous observations from HARPS with the goal of evaluating the presence of orbiting planets. Using different noise models within a general Bayesian framework designed for planet detection in RV data, we test the significance of the various signals present in the HD41248 dataset. We use Gaussian processes as well as a first-order moving average component to try to correct for activity-induced signals. At the same time, we analyse photometry from the TESS mission, searching for transits and rotational modulation in the light curve. The number of significantly detected Keplerian signals depends on the noise model employed, which can range from 0 with the Gaussian process model to 3 with a white noise model. We find that the Gaussian process alone can explain the RV data while allowing for the stellar rotation period and active region evolution timescale to be constrained. The rotation period estimated from the RVs agrees with the value determined from the TESS light curve. Based on the data that is currently available, we conclude that the RV variations of HD41248 can be explained by stellar activity (using the Gaussian process model) in line with the evidence from activity indicators and the TESS photometry.

[50]  arXiv:1911.11730 [pdf, other]
Title: Automatic detection of full ring galaxy candidates in SDSS
Authors: Lior Shamir
Comments: MNRAS, accepted
Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

A full ring is a form of galaxy morphology that is not associated with a specific stage on the Hubble sequence. Digital sky surveys can collect many millions of galaxy images, and therefore even rare forms of galaxies are expected to be present in relatively large numbers in image databases created by digital sky surveys. Sloan Digital Sky Survey (SDSS) data release (DR) 14 contains ~2.6*10^6 objects with spectra identified as galaxies. The method described in this paper applied automatic detection to identify a set of 443 ring galaxy candidates, 104 of them were already included in the Buta + 17 catalogue of ring galaxies in SDSS, but the majority of the galaxies are not included in previous catalogues. Machine analysis cannot yet match the superior pattern recognition abilities of the human brain, and even a small false positive rate makes automatic analysis impractical when scanning through millions of galaxies. Reducing the false positive rate also increases the true negative rate, and therefore the catalogue of ring galaxy candidates is not exhaustive. However, due to its clear advantage in speed, it can provide a large collection of galaxies that can be used for follow-up observations of objects with ring morphology.

[51]  arXiv:1911.11734 [pdf, other]
Title: Estimating trajectories of meteors: an observational Monte Carlo approach -- II. Results
Comments: Accepted for publication in MNRAS, 16 pages
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

In the first paper of this series we examined existing methods of optical meteor trajectory estimation and developed a novel method which simultaneously uses both the geometry and the dynamics of meteors to constrain their trajectories. We also developed a simulator which uses an ablation model to generate realistic synthetic meteor trajectories which we use to test meteor trajectory solvers. In this second paper, we perform simulation validation to estimate radiant and velocity accuracy which may be achieved by various meteor observation systems as applied to several meteor showers. For low-resolution all-sky systems, where the meteor deceleration is generally not measurable, the multi-parameter fit method assuming a constant velocity better reproduces the radiant and speed of synthetic meteors. For moderate field of view systems, our novel method performs the best at all convergence angles, while multi-parameter fit methods generally produce larger speed errors. For high-resolution, narrow field of view systems, we find our new method of trajectory estimation reproduces radiant and speed more accurately than all other methods tested. The ablation properties of meteoroids are commonly found to be the limiting factor in velocity accuracy. We show that the true radiant dispersion of meteor showers can be reliably measured with moderate field of view (or more precise) systems provided appropriate methods of meteor trajectory estimation are employed. Finally, we compare estimated and real angular radiant uncertainty and show that for the solvers tested the real radiant error is on average underestimated by a factor of two.

[52]  arXiv:1911.11735 [pdf, other]
Title: Photometric asymmetry between galaxies with opposite spin patterns: A comparison of three telescopes
Authors: Lior Shamir
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The spin pattern of a spiral galaxy is a matter of the perspective of the observer, and therefore galaxies with clockwise spin patterns are expected to be identical in their characteristics to galaxies with counterclockwise spin patterns. However, observations of a large number of galaxies show clear photometric differences between clockwise and counterclockwise spiral galaxies. In this study the magnitude difference between clockwise and counterclockwise spiral galaxies imaged by the space-based COSMOS survey is compared to galaxies imaged by the Earth-based SDSS and PanSTARRS around the same field. The comparison shows that the same asymmetry was identified by all three telescopes, providing strong evidence that the rotation direction of the galaxy affects its magnitude as measured from Earth. Analysis of a large number of galaxies from different parts of the sky shows that the differences between clockwise and counterclockwise galaxies are oriented around an axis such that the photometric asymmetry in one hemisphere is inverse to the photometric asymmetry in the opposite hemisphere. Due to the provocative nature of the observation, it is difficult to identify an immediate explanation. A possible explanation could be related to the large-scale structure of the universe, which leads to violation of the cosmological homogeneity assumption. Another possible explanation that does not require the violation of the cosmological principle is that the observation is driven by galaxy rotation. Due to relativistic beaming, such difference is indeed expected to be identified and peak at the galactic pole, but it is expected to be far smaller than the differences observed by all three telescopes. Therefore, if the asymmetry is driven by galaxy rotation, it corresponds to a much higher velocity than the actual measured rotational velocity of galaxies.

[53]  arXiv:1911.11755 [pdf, other]
Title: AION: An Atom Interferometer Observatory and Network
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Experiment (hep-ex); High Energy Physics - Phenomenology (hep-ph); Atomic Physics (physics.atom-ph)

We outline the experimental concept and key scientific capabilities of AION (Atom Interferometer Observatory and Network), a proposed UK-based experimental programme using cold strontium atoms to search for ultra-light dark matter, to explore gravitational waves in the mid-frequency range between the peak sensitivities of the LISA and LIGO/Virgo/ KAGRA/INDIGO/Einstein Telescope/Cosmic Explorer experiments, and to probe other frontiers in fundamental physics. AION would complement other planned searches for dark matter, as well as probe mergers involving intermediate mass black holes and explore early universe cosmology. AION would share many technical features with the MAGIS experimental programme in the US, and synergies would flow from operating AION in a network with this experiment, as well as with other atom interferometer experiments such as MIGA, ZAIGA and ELGAR. Operating AION in a network with other gravitational wave detectors such as LIGO, Virgo and LISA would also offer many synergies.

[54]  arXiv:1911.11760 [pdf, other]
Title: Early dark energy from massive neutrinos -- a natural resolution of the Hubble tension
Comments: five pages, three figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

The Hubble tension can be significantly eased if there is an early component of dark energy that becomes active around the time of matter-radiation equality. Early dark energy models suffer from a coincidence problem---the physics of matter-radiation equality and early dark energy are completely disconnected, so some degree of fine-tuning is needed in order for them to occur nearly simultaneously. In this paper we propose a natural explanation for this coincidence. If the early dark energy scalar couples to neutrinos then it receives a large injection of energy around the time that neutrinos become non-relativistic. This is precisely when their temperature is of order their mass, which, coincidentally, occurs around the time of matter-radiation equality. Neutrino decoupling therefore provides a natural trigger for early dark energy by displacing the field from its minimum just before matter-radiation equality. We discuss various theoretical aspects of this proposal, potential observational signatures, and future directions for its study.

[55]  arXiv:1911.11761 [pdf, ps, other]
Title: An accurate analytic model for the lensing mass of galaxies
Comments: 26 pages, 16 figures, 1 table; Submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We develop an analytic model for the lensing mass of galaxies, based on a broken power-law (BPL) density profile, which is a power-law profile with a mass deficit or surplus in the central region. Under the assumption of an elliptically symmetric surface mass distribution, the deflection angle and magnification can be evaluated analytically for this new model. We compute the theoretical prediction of various quantities, including the volume and surface mass density profiles of the galaxies, and the aperture and luminosity (AL)-weighted line-of-sight velocity dispersions (LOSVDs), and compare to those measured from the Illustris simulation. We find an excellent agreement between our model prediction and the simulation, which validates our modeling. The high efficiency and accuracy of our model manifests itself a promising tool for studying properties of galaxies with strong lensing.

[56]  arXiv:1911.11766 [pdf, other]
Title: Measuring lensing ratios with future cosmological surveys
Comments: 14 pages, 11 figures, 1 table
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

The ratio between the CMB lensing/galaxy counts and the galaxy shear/galaxy counts cross-correlations combines the information from different cosmological probes to infer cosmographic measurements that are less dependent on astrophysical uncertainties and can constrain the geometry of the Universe. We discuss the future perspectives for the measurement of this lensing ratio as previously introduced, i.e. with the use of the Limber and flat-sky approximations and neglecting all the effects on the galaxy survey from observing on the past lightcone. We then show how the cosmological information in this estimator is affected by the Limber approximation and by the inclusion of the redshift space distorsions (RSD) and magnification lensing contributions to the galaxy number counts. We find that the magnification lensing contribution induces a multipole dependence of the lensing ratio that we show to be detectable at a statistical significant level combining post-$Planck$ CMB surveys and a Euclid-like experiment. We propose an improved estimator which takes into account this angular scale dependence. Using this extended formalism, we present forecasts for upcoming and future cosmological surveys and we show at which extent the lensing ratio information can improve the CMB constraints on cosmological parameters. We get that for extended cosmological models where the spatial curvature and the dark energy equation of state are allowed to vary, the constraints from $Planck$ on these parameters and on $H_0$ can be reduced by $\lesssim 40\%$ with the inclusion of the lensing ratio. We also find that neglegcting the contribution from magnification lensing can induce a bias on the derived cosmological parameters in a combined analysis.

Cross-lists for Wed, 27 Nov 19

[57]  arXiv:1911.10918 (cross-list from gr-qc) [pdf, ps, other]
Title: Quantum Cosmology and the Inflationary Spectra from a Non-Minimally Coupled Inflaton
Comments: 24 pages, no figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)

We calculate the quantum gravitational corrections to the Mukhanov-Sasaki equation obtained by the canonical quantization of the inflaton-gravity system. Our approach, which is based on the Born-Oppenheimer decomposition of the resulting Wheeler-DeWitt equation, was previously applied to a minimally coupled inflaton. In this article we examine the case of a non minimally coupled inflaton and, in particular, the induced gravity case is also discussed. Finally, the equation governing the quantum evolution of the inflationary perturbations is derived on a de Sitter background. Moreover the problem of the introduction of time is addressed and a generalized method, with respect to that used for the minimal coupling case, is illustrated. Such a generalized method can be applied to the universe wave function when, through the Born-Oppenheimer factorization, we decompose it into a part which contains the minisuperspace degrees of freedom and another which describes the perturbations.

[58]  arXiv:1911.11495 (cross-list from gr-qc) [pdf, ps, other]
Title: Entropy Production in Affine Inflation
Comments: 12 pages
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)

Multiple scalar fields nonminimally interacting through pure affine gravity are considered to generate primordial perturbations during an inflationary phase. The couplings considered give rise to two distinct sources of entropy perturbations that may not be suppressed in the long wavelength limit. The first is merely induced by the presence of more than one scalar and arises even in the minimal coupling limit. The second source however is restricted to nonminimal interaction. Unlike the case of metric gravity, and due to the absence of anisotropic stresses, the second source disappears for single scalar, showing that nonminimal couplings become relevant to non-adiabatic perturbations only when more than one scalar field are considered. Hence the notion of adiabaticity is not affected by the transition to minimal coupling contrary to the metric gravity case where it becomes frame-dependent. Precise data that might be able to neatly track different sources of isocurvature modes, if any, must not only distinguish between different models of inflation but also determine the most viable approach to gravity which underlies the inflationary dynamics itself.

[59]  arXiv:1911.11513 (cross-list from gr-qc) [pdf, other]
Title: Reheating in $R^2$ Palatini inflationary models
Comments: 34 pages, 12 figures, pdflatex
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We consider $R^2$ inflation in the Palatini gravity assuming the existence of scalar fields, coupled to gravity in the most general manner. These theories, in the Einstein frame, and for one scalar field $h$, share common features with $K$ - inflation models. We apply this formalism for the study of popular inflationary models, whose potentials are monomials, $ V \sim h^{n} $, with $ n $ a positive even integer. We also study the Higgs model non-minimally coupled to gravity. Although these have been recently studied, in the framework of the Palatini approach, we show that the scalar power spectrum severely constrains these models. Although we do not propose a particular reheating mechanism, we show that the quadratic $ \sim h^2$ and the Higgs model can survive these constraints with a maximum reheating temperature as large as $ \sim 10^{15} \, GeV$, when reheating is instantaneous. However, this can be only attained at the cost of a delicate fine-tuning of couplings. Deviations from this fine-tuned values can still yield predictions compatible with the cosmological data, for couplings that lie in very tight range, giving lower reheating temperatures.

Replacements for Wed, 27 Nov 19

[60]  arXiv:1306.2144 (replaced) [pdf, other]
Title: Importance Nested Sampling and the MultiNest Algorithm
Comments: 28 pages, 6 figures, 2 tables. Accepted for publication in The Open Journal of Astrophysics. Code available from this https URL
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (physics.data-an); Computation (stat.CO)
[61]  arXiv:1411.3740 (replaced) [pdf, ps, other]
Title: Multi-brid DBI Inflation
Comments: improved version
Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[62]  arXiv:1612.07855 (replaced) [pdf, other]
Title: Testing parity-violating physics from cosmic rotation power reconstruction
Authors: Toshiya Namikawa (Stanford, SLAC)
Comments: 10 pages, 6 figures, minor typo corrected
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
[63]  arXiv:1808.06646 (replaced) [pdf, other]
Title: Measuring the temperature and profiles of Lyman-$α$ absorbers
Comments: Added new method including the median flux, 12 figure, 15 pages
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[64]  arXiv:1809.04408 (replaced) [pdf, ps, other]
Title: Gravitational instability caused by the weight of heat
Authors: Zacharias Roupas
Journal-ref: Symmetry 2019, 11(12), 1435
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Theory (hep-th)
[65]  arXiv:1901.00900 (replaced) [pdf, ps, other]
Title: High-Precision Dark Halo Virial Masses from Globular Cluster Numbers: Implications for Globular Cluster Formation and Galaxy Assembly
Comments: 11 pages, 4 figures, ApJ in press
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[66]  arXiv:1904.07923 (replaced) [pdf, other]
Title: Measurement of the spin of the M87 black hole from its observed twisted light
Comments: Small addition on coherence. 5 pages, 2 figures Accepted for publication in MNRAS Letters
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[67]  arXiv:1904.11993 (replaced) [pdf, other]
Title: Supernovae Sparked By Dark Matter in White Dwarfs
Comments: 41 pages, 5 figures, PRD version
Journal-ref: Phys. Rev. D 100, 043020 (2019)
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
[68]  arXiv:1905.10393 (replaced) [pdf, other]
Title: Reconciling spontaneous scalarization with cosmology
Comments: 16 pages, v2 matches published version
Journal-ref: Phys. Rev. D 100, 104051 (2019)
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[69]  arXiv:1906.06109 (replaced) [pdf, other]
Title: One simulation to have them all: performance of the Bias Assignment Method against N-body simulations
Comments: Accepted for publication at MNRAS
Journal-ref: MNRAS 2019
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[70]  arXiv:1906.09930 (replaced) [pdf, other]
Title: Dark matter as Planck relics without too exotic hypotheses
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[71]  arXiv:1907.01002 (replaced) [pdf, other]
Title: Detectability of Collective Neutrino Oscillation Signatures in the Supernova Explosion of a 8.8 $M_\odot$ star
Comments: 18 pages, 15 figures, submitted to PRD
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[72]  arXiv:1907.03574 (replaced) [pdf, other]
Title: The local properties of supernova explosions and their host galaxies
Comments: 19 pages, 10 figures
Journal-ref: Research in Astronomy and Astrophysics, 19, 121 (2019)
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[73]  arXiv:1907.05243 (replaced) [pdf, other]
Title: Spectral signatures of recursive magnetic field reconnection
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)
[74]  arXiv:1907.07558 (replaced) [pdf, other]
[75]  arXiv:1909.08279 (replaced) [pdf, other]
Title: The 3HSP catalogue of Extreme & High Synchrotron Peaked Blazars
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[76]  arXiv:1909.10952 (replaced) [pdf, ps, other]
Title: Kruger 60 as a home system for 2I/Borisov -- a case study
Comments: 11 pages, 5 tables, 3 figures, a highly extended version
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
[77]  arXiv:1909.11196 (replaced) [pdf, other]
Title: Occurrence of semiclassical vacuum decay
Authors: Shao-Jiang Wang
Comments: v1, 9 pages, 6 figures; v2, to match the published version in PRD, title slightly changed by editor
Journal-ref: Phys.Rev.D100(2019)096019
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[78]  arXiv:1911.01757 (replaced) [pdf, other]
Title: Internal magnetic fields, spin-orbit coupling, and orbital period modulation in close binary systems
Authors: A. F. Lanza (INAF-Catania, Italy)
Comments: 13 pages, 2 figures, 3 tables, one Appendix; accepted by Monthly Notices of the Royal Astronomical Society
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
[79]  arXiv:1911.04359 (replaced) [pdf, other]
Title: Relativistic and non-Gaussianity contributions to the one-loop power spectrum
Comments: 19 pages, 6 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[80]  arXiv:1911.09758 (replaced) [pdf, other]
Title: Atmospheric Characterization and Further Orbital Modeling of $κ$ And b
Comments: accepted for publication in AJ, typo fixed in ver.2
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[81]  arXiv:1911.10253 (replaced) [pdf, ps, other]
Title: Variable warm dust around the Herbig Ae star HD~169142: Birth of a ring?
Comments: 7 pages, 3 figures. Accepted to ApJ Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
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