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

Astrophysics

New submissions

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New submissions for Mon, 24 Feb 20

[1]  arXiv:2002.08960 [pdf]
Title: A Theoretical Investigation of the Possible Detection of C24 in Space
Comments: 15 pages, 4 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR); Chemical Physics (physics.chem-ph)

Astronomical infrared spectral features at ~6.6, 9.8 and 20 micronm have recently been suggested as being due to the planar graphene form of C24 carbon cluster. Here we report density functional theory and coupled cluster calculations on wavefunctions stability, relative energies, and infrared spectra of four different types of C24 isomers, including the graphene and fullerene forms. The types of vibrational motions under these bands are also discussed. Among the four isomers, we find that the astronomical data are best approximated by the graphene form of C24.

[2]  arXiv:2002.08961 [pdf, ps, other]
Title: The Importance Of Star Formation Intensity In LYα Escape From Green Pea Galaxies And Lyman Break Galaxy Analogs
Comments: 8 pages, 3 figures, 2 tables. Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We have studied ultraviolet images of 40 Green Pea galaxies and 15 local Lyman Break Galaxy Analogs to understand the relation between Ly$\alpha$ photon escape and central UV photometric properties. We measured star formation intensity (SFI, star formation rate per unit area) from the central 250 pc region ($S_{\rm 250pc}$) using COS/NUV images from the \textit{Hubble Space Telescope}. The measured $S_{\rm 250pc}$ of our sample Green Peas ranges from 2.3--46 $M_{\odot} \ \rm{year}^{-1} \ \rm{kpc^{-2}}$, with a geometric mean of $15 M_{\odot} \ \rm{year}^{-1} \ \rm{kpc^{-2}}$ and a standard deviation of 0.266 dex, forming a relatively narrow distribution. The Lyman Break Galaxy Analogs show a similarly narrow distribution of $S_{\rm 250pc}$ (0.271 dex), though with a larger mean of 28 $M_{\odot} \ \rm{year}^{-1} \ \rm{kpc^{-2}}$. We show that while the Ly$\alpha$ equivalent width (EW(Ly$\alpha$)) and the Ly$\alpha$ escape fraction ($f^{Ly\alpha}_{esc}$) are not significantly correlated with the central SFI ($S_{\rm 250pc}$), both are positively correlated with the ratio of surface brightness to galaxy stellar mass ($S_{\rm 250pc}/M_{\rm star}$), with correlation coefficients ($p$-values) of 0.702 ($1\times 10^{-8}$) and 0.529 ($5\times 10^{-4}$) with EW(Ly$\alpha$) and $f^{Ly\alpha}_{esc}$, respectively. These correlations suggest a scenario where intense central star formation can drive a galactic wind in galaxies with relatively shallow gravitational potential wells, thus clearing channels for the escape of Ly$\alpha$ photons.

[3]  arXiv:2002.08962 [pdf, other]
Title: Gravitational microlensing by dark matter in extended structures
Comments: 11 pages revtex4, 5 figures, 1 table
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

Dark matter may be in the form of non-baryonic structures such as compact subhalos and boson stars. Structures weighing between asteroid and solar masses may be discovered via gravitational microlensing, an astronomical probe that has in the past helped constrain the population of primordial black holes and baryonic MACHOs. We investigate the non-trivial effect of the size of and density distribution within these structures on the microlensing signal, and constrain their populations using the EROS-2 and OGLE-IV surveys. Structures larger than a solar radius are generally constrained more weakly than point-like lenses, but stronger constraints may be obtained for structures with mass distributions that give rise to caustic crossings or produce larger magnifications.

[4]  arXiv:2002.08964 [pdf, other]
Title: Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-Forming Galaxies
Comments: 28 pages + 3 appendices, ApJ in press. See this https URL for a short video describing the main results. Data tables available at this https URL prior to publication
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We compare the observed turbulent pressure in molecular gas, $P_\mathrm{turb}$, to the required pressure for the interstellar gas to stay in equilibrium in the gravitational potential of a galaxy, $P_\mathrm{DE}$. To do this, we combine arcsecond resolution CO data from PHANGS-ALMA with multi-wavelength data that traces the atomic gas, stellar structure, and star formation rate (SFR) for 28 nearby star-forming galaxies. We find that $P_\mathrm{turb}$ correlates with, but almost always exceeds the estimated $P_\mathrm{DE}$ on kiloparsec scales. This indicates that the molecular gas is over-pressurized relative to the large-scale environment. We show that this over-pressurization can be explained by the clumpy nature of molecular gas; a revised estimate of $P_\mathrm{DE}$ on cloud scales, which accounts for molecular gas self-gravity, external gravity, and ambient pressure, agrees well with the observed $P_\mathrm{turb}$ in galaxy disks. We also find that molecular gas with cloud-scale ${P_\mathrm{turb}}\approx{P_\mathrm{DE}}\gtrsim{10^5\,k_\mathrm{B}\,\mathrm{K\,cm^{-3}}}$ in our sample is more likely to be self-gravitating, whereas gas at lower pressure appears more influenced by ambient pressure and/or external gravity. Furthermore, we show that the ratio between $P_\mathrm{turb}$ and the observed SFR surface density, $\Sigma_\mathrm{SFR}$, is compatible with stellar feedback-driven momentum injection in most cases, while a subset of the regions may show evidence of turbulence driven by additional sources. The correlation between $\Sigma_\mathrm{SFR}$ and kpc-scale $P_\mathrm{DE}$ in galaxy disks is consistent with the expectation from self-regulated star formation models. Finally, we confirm the empirical correlation between molecular-to-atomic gas ratio and kpc-scale $P_\mathrm{DE}$ reported in previous works.

[5]  arXiv:2002.08965 [pdf, other]
Title: The evolving AGN duty cycle in galaxies since z$\sim$3 as encoded in the X-ray luminosity function
Comments: Accepted for publication in ApJ. 25 pages, 15 figures, 2 tables. The best X-ray luminosity functions are available at this https URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present a new modeling of the X-ray luminosity function (XLF) of Active Galactic Nuclei (AGN) out to z$\sim$3, dissecting the contribution of main-sequence (MS) and starburst (SB) galaxies. For each galaxy population, we convolved the observed galaxy stellar mass (M$_{\star}$) function with a grid of M$_{\star}$-independent Eddington ratio ($\lambda_{\rm EDD}$) distributions, normalised via empirical black hole accretion rate (BHAR) to star formation rate (SFR) relations. Our simple approach yields an excellent agreement with the observed XLF since z$\sim$3. We find that the redshift evolution of the observed XLF can only be reproduced through an intrinsic flattening of the $\lambda_{\rm EDD}$ distribution, and with a positive shift of the break $\lambda^{*}$, consistent with an anti-hierarchical behavior. The AGN accretion history is predominantly made by massive (10$^{10}<$M$_{\star}<$10$^{11}$ M$_{\odot}$) MS galaxies, while SB-driven BH accretion, possibly associated with galaxy mergers, becomes dominant only in bright quasars, at $\log$(L$_{\rm X}$/erg s$^{-1}$)$>$44.36 + 1.28$\cdot$(1+z). We infer that the probability of finding highly-accreting ($\lambda_{\rm EDD}>$ 10%) AGN significantly increases with redshift, from 0.4% (3.0%) at z=0.5 to 6.5% (15.3%) at z=3 for MS (SB) galaxies, implying a longer AGN duty cycle in the early Universe. Our results strongly favor a M$_{\star}$-dependent ratio between BHAR and SFR, as BHAR/SFR $\propto$ M$_{\star}^{0.73[+0.22,-0.29]}$, supporting a non-linear BH buildup relative to the host. Finally, this framework opens potential questions on super-Eddington BH accretion and different $\lambda_{\rm EDD}$ prescriptions for understanding the cosmic BH mass assembly.

[6]  arXiv:2002.08966 [pdf, other]
Title: Studying the ISM at ~10 pc scale in NGC 7793 with MUSE -- I. Data description and properties of the ionised gas
Comments: Accepted for publication in A&A. 24 pages, 19 figures. Please see journal article for high resolution figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Using MUSE AO data, we probe the ISM in the local spiral galaxy NGC 7793 at a spatial resolution of $\sim$ 10 pc. We identify HII regions and compile a catalogue of supernova remnants (SNRs), planetary nebulae (PNe) and Wolf Rayet stars (WR). We compute electron densities and temperatures from the [SII]6716/6731 and [SIII]6312/9069 line ratios. We study the properties of the ionised gas through BPT diagrams combined with gas velocity dispersion. We spectroscopically confirm 2 previously detected WR stars and a SNR and report the discovery of 7 WR, 1 SNR, and 2 PNe. The diffuse ionized gas (DIG) fraction is between $\sim$ 27 and 42% depending on the method used to define the HII region boundaries. In agreement with previous studies, we find that the DIG exhibits enhanced [SII]/H$\alpha$ and [NII]/H$\alpha$ ratios and a median temperature that is $\sim$ 3000 K higher than in HII regions. We also observe an apparent inverse correlation between temperature and H$\alpha$ surface brightness. Overall, the observed [SII]6716/6731 ratio is consistent within 1$\sigma$ with $n_e$ < 30 cm$^{-3}$, with an almost identical distribution for the DIG and HII regions. The velocity dispersion of the ionised gas indicates that the DIG has a higher degree of turbulence than the HII regions. Comparison with photoionisation and shock models reveals that the diffuse component can only partially be explained via shocks and that it is most likely consistent with photons leaking from density bounded HII regions or with radiation from evolved field stars. [abridged]

[7]  arXiv:2002.08967 [pdf, other]
Title: X-ray quasi-periodic eruptions from the galactic nucleus of RX J1301.9+2747
Comments: 8 pages, 4 figures, 2 tables; under review
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Following the recent discovery of X-ray quasi-periodic eruptions (QPEs) from the nucleus of the galaxy GSN 069, we report here on the detection of QPEs in the active galaxy RX J1301.9+2747. QPEs are rapid and recurrent increases of the X-ray count-rate by more than one order of magnitude with respect to a stable quiescent level. During a 48 ks long XMM-Newton observation performed on 30 and 31 May 2019, three strong QPEs lasting about half an hour each were detected in the light curves of RX J1301.9+2747. The first two QPEs are separated by a much longer recurrence time (about 20 ks) compared to the second and third (about 13 ks); this pattern is consistent with the alternating long-short recurrence times of the GSN 069 QPEs. Longer X-ray observations will better clarify the temporal pattern of the QPEs in RX J1301.9+2747 and will allow to perform a detailed comparison with GSN 069. The X-ray spectral properties of QPEs in the two sources are remarkably similar, with QPEs representing fast transitions from a relatively cold and likely disc-dominated state to a state characterized by warmer emission similar to the so-called soft X-ray excess, a component that is almost ubiquitously seen in the X-ray spectra of unobscured, radiatively efficient active galaxies. Previous X-ray observations of RX J1301.9+2747 in 2000 and 2009 strongly suggest that QPEs have been present for at least the past 18.5 years. The detection of QPEs from a second galactic nucleus after GSN 069 rules out contamination by a Galactic source in both cases, so that QPEs have to be considered as a novel extragalactic phenomenon associated with accreting supermassive black holes.

[8]  arXiv:2002.08977 [pdf, other]
Title: Properties of giant molecular clouds in the strongly barred galaxy NGC1300
Comments: 23 pages, 13 figures, accepted for publication in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Star formation activity depends on galactic-scale environments. To understand the variations in star formation activity, comparing the properties of giant molecular clouds (GMCs) among environments with different star formation efficiency (SFE) is necessary. We thus focus on a strongly barred galaxy to investigate the impact of the galactic environment on the GMCs properties, because the SFE is clearly lower in bar regions than in arm regions. In this paper, we present the $^{12}$CO($1-0$) observations toward the western bar, arm and bar-end regions of the strongly barred galaxy NGC1300 with ALMA 12-m array at a high angular resolution of $\sim$40 pc. We detected GMCs associated with the dark lanes not only in the arm and bar-end regions but also in the bar region, where massive star formation is not seen. Using the CPROPS algorithm, we identified and characterized 233 GMCs across the observed regions. Based on the Kolmogorov-Smirnov test, we find that there is virtually no significant variations in GMC properties (e.g., radius, velocity dispersion, molecular gas mass, and virial parameter) among the bar, arm and bar-end region. These results suggest that systematic differences in the physical properties of the GMCs are not the cause for SFE differences with environments, and that there should be other mechanisms which control the SFE of the GMCs such as fast cloud-cloud collisions in NGC1300.

[9]  arXiv:2002.08978 [pdf, other]
Title: The OTELO survey. A case study of [O III]4959,5007 emitters at <z> = 0.83
Comments: 16 pages, 6 figures. Accepted in Astronomy \& Astrophysics
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The OTELO survey is a very deep, blind exploration of a selected region of the Extended Groth Strip and is designed for finding emission-line sources (ELSs). The survey design, observations, data reduction, astrometry, and photometry, as well as the correlation with ancillary data used to obtain a final catalogue, including photo-z estimates and a preliminary selection of ELS, were described in a previous contribution. Here, we aim to determine the main properties and luminosity function (LF) of the [O III] ELS sample of OTELO as a scientific demonstration of its capabilities, advantages, and complementarity with respect to other surveys. The selection and analysis procedures of ELS candidates obtained using tunable filter (TF) pseudo-spectra are described. We performed simulations in the parameter space of the survey to obtain emission-line detection probabilities. Relevant characteristics of [O III] emitters and the LF([O III]), including the main selection biases and uncertainties, are presented. A total of 184 sources were confirmed as [O III] emitters at a mean redshift z=0.83. The minimum detectable line flux and equivalent width (EW) in this ELS sample are $\sim$5 $\times$ 10$^{-19}$ erg s$^{-1}$ cm$^{2}$ and $\sim$6 \AA, respectively. We are able to constrain the faint-end slope ($\alpha = -1.03\pm0.08$) of the observed LF([O III]) at z=0.83. This LF reaches values that are approximately ten times lower than those from other surveys. The vast majority (84\%) of the morphologically classified [O III] ELSs are disc-like sources, and 87\% of this sample is comprised of galaxies with stellar masses of M$_\star$ $<$ 10$^{10}$ M$_{\odot}$.

[10]  arXiv:2002.08980 [pdf, other]
Title: The Open Cluster Chemical Abundances and Mapping Survey: IV. Abundances for 128 Open Clusters using SDSS/APOGEE DR16
Comments: 17 pages, 14 figures, Accepted for publication by AJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The Open Cluster Chemical Abundances and Mapping (OCCAM) survey aims to constrain key Galactic dynamical and chemical evolution parameters by the construction of a large, comprehensive, uniform, infrared-based spectroscopic data set of hundreds of open clusters. This fourth contribution from the OCCAM survey presents analysis using SDSS/APOGEE DR16 of a sample of 128 open clusters, 71 of which we designate to be "high quality" based on the appearance of their color-magnitude diagram. We find the APOGEE DR16 derived [Fe/H] abundances to be in good agreement with previous high resolution spectroscopic open cluster abundance studies. Using the high quality sample, we measure Galactic abundance gradients in 16 elements, and find evolution of some of the [X/Fe] gradients as a function of age. We find an overall Galactic [Fe/H] vs R_GC gradient of $-0.068 \pm 0.001$ dex kpc$^{-1}$ over the range of $6 <$ R_GC $< 13.9$ kpc; however, we note that this result is sensitive to the distance catalog used, varying as much as 15%. We formally derive the location a break in the [Fe/H] abundance gradient as a free parameter in the gradient fit for the first time. We also measure significant Galactic gradients in O, Mg, S, Ca, Mn, Cr, Cu, Na, Al, and K, some of which are measured for the first time. Our large sample allows us to explore four well-populated age bins to explore the time evolution of gradients for a large number of elements and comment on possible implications for Galactic chemical evolution and radial migration.

[11]  arXiv:2002.08997 [pdf, ps, other]
Title: Study of the decay rates of the umbral area of sunspot groups by using a high resolution database
Authors: Judit Muraközy
Comments: 10 pages, 8 figures, accepted for publication in the ApJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

The emergence and decay of the sunspot groups are important components of the solar dynamo models. There are two different types of studies on the evolution of active regions. One of them is based on fewer data with higher spatial resolution, the other one uses more data with lower spatial resolution. The input data of the present study allow the investigation with high-resolution both spatially and temporally. The temporal resolution of the SoHO Debrecen Sunspot Database (SDD) is one and a half hours, and it also makes possible to identify all individual sunspots with the position, area, and magnetic polarity. More than 200 sunspot groups have been selected, which have clear maxima on the solar disc, and the decrease of their umbral area is observable during at least four days. The decay rates were calculated by using two data: the umbral area and the number of contained sunspots -- these decay rates were computed for the total umbral area of sunspot groups and their leading and following parts. The decay rate has a linear area dependency, and it is higher for the following part than for the leading one.

[12]  arXiv:2002.09008 [pdf, other]
Title: Potential Themis Family Asteroid Contribution to the Jupiter-Family Comet Population
Comments: 12 pages, 6 figures; accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Recent dynamical analyses suggest that some Jupiter family comets (JFCs) may originate in the main asteroid belt instead of the outer solar system. This possibility is particularly interesting given evidence that icy main-belt objects are known to be present in the Themis asteroid family. We report results from dynamical analyses specifically investigating the possibility that icy Themis family members could contribute to the observed population of JFCs. Numerical integrations show that such dynamical evolution is indeed possible via a combination of eccentricity excitation apparently driven by the nearby 2:1 mean-motion resonance with Jupiter, gravitational interactions with planets other than Jupiter, and the Yarkovsky effect. We estimate that, at any given time, there may be tens of objects from the Themis family on JFC-like orbits with the potential to mimic active JFCs from the outer solar system, although not all, or even any, may necessarily be observably active. We find that dynamically evolved Themis family objects on JFC-like orbits have semimajor axes between 3.15 au and 3.40 au for the vast majority of their time on such orbits, consistent with the strong role that the 2:1 mean-motion resonance with Jupiter likely plays in their dynamical evolution. We conclude that a contribution from the Themis family to the active JFC population is plausible, although further work is needed to better characterize this contribution.

[13]  arXiv:2002.09011 [pdf, other]
Title: SDSS-IV MaNGA: The kinematic-morphology of galaxies on the mass vs star-formation relation in different environments
Comments: 19 pages, 8 figures, LaTeX. Submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the link between the kinematic-morphology of galaxies, as inferred from integral-field stellar kinematics, and their relation between mass and star formation rate (SFR). Our sample consists of $\sim 3200$ galaxies with integral-field spectroscopic data from the MaNGA survey with available determinations of their effective stellar angular momentum within the half-light radius $\lambda_{R_e}$. We find that for star-forming galaxies, namely along the star formation main sequence (SFMS), the $\lambda_{R_e}$ values remain large and almost unchanged over about two orders of magnitude in stellar mass, with the exception of the lowest masses $\mathcal{M}_{\star}\lesssim2\times10^{9} \mathcal{M}_{\odot}$, where $\lambda_{R_e}$ slightly decreases. The SFMS is dominated by spiral galaxies with small bulges. Below the SFMS, but above the characteristic stellar mass $\mathcal{M}_{\rm crit}\approx2\times10^{11} \mathcal{M}_{\odot}$, there is a sharp decrease in $\lambda_{R_e}$ with decreasing star formation rate: massive galaxies well below the SFMS are mainly slow-rotator early-type galaxies, namely genuinely spheroidal galaxies without disks. Below the SFMS and below $\mathcal{M}_{\rm crit}$ the decrease of $\lambda_{R_e}$ with decreasing SFR becomes modest or nearly absent: low-mass galaxies well below the SFMS, are fast-rotator early-type galaxies, and contain fast-rotating stellar disks like their star-forming counterparts. We also find a small but clear environmental dependence for the massive galaxies: in the mass range $10^{10.9}-10^{11.5} \mathcal{M}_{\odot}$, galaxies in rich groups or denser regions or classified as central galaxies have lower values of $\lambda_{R_e}$. While no environmental dependence is found for galaxies of lower mass. We discuss how our results can be understood as due to the different star formation and mass assembly histories of galaxies with varying mass.

[14]  arXiv:2002.09042 [pdf, other]
Title: Chemical Diversity of Super-Earths As a Consequence of Formation
Comments: 15 pages, 14 figures. Accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Recent observations of rocky super-Earths have revealed an apparent wider distribution of Fe/Mg ratios, or core to mantle ratios, than the planets in our Solar System. This study aims to understand how much of the chemical diversity in the super-Earth population can arise from giant impacts during planetary formation. Planet formation simulations have only recently begun to treat collisions more realistically in an attempt to replicate the planets in our Solar System. We investigate planet formation more generally by simulating the formation of rocky super-Earths with varying initial conditions using a version of SyMBA, a gravitational N-body code, that incorporates realistic collisions. We track the maximum plausible change in composition after each impact. The final planets span a range of Fe/Mg ratios similar to the Solar System planets, but do not completely match the distribution in super-Earth data. We only form a few planets with minor iron-depletion, suggesting other mechanisms are at work. The most iron-rich planets have a lower Fe/Mg ratio than Mercury, and are less enriched than planets such as Kepler-100b. This indicates that further work on our understanding of planet formation and further improvement of precision of mass and radius measurements are required to explain planets at the extremes of this Fe/Mg distribution.

[15]  arXiv:2002.09058 [pdf, other]
Title: Probing UV-Sensitive Pathways for CN and HCN Formation in Protoplanetary Disks with the Hubble Space Telescope
Comments: Accepted for publication in AJ
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

The UV radiation field is a critical regulator of gas-phase chemistry in surface layers of disks around young stars. In an effort to understand the relationship between photocatalyzing UV radiation fields and gas emission observed at infrared and sub-mm wavelengths, we present an analysis of new and archival HST, Spitzer, ALMA, IRAM, and SMA data for five targets in the Lupus cloud complex and 14 systems in Taurus-Auriga. The HST spectra were used to measure LyA and FUV continuum fluxes reaching the disk surface, which are responsible for dissociating relevant molecular species (e.g. HCN, N2). Semi-forbidden C II] 2325 and UV-fluorescent H2 emission were also measured to constrain inner disk populations of C+ and vibrationally excited H2. We find a significant positive correlation between 14 micron HCN emission and fluxes from the FUV continuum and C II] 2325, consistent with model predictions requiring N2 photodissociation and carbon ionization to trigger the main CN/HCN formation pathways. We also report significant negative correlations between sub-mm CN emission and both C II] and FUV continuum fluxes, implying that CN is also more readily dissociated in disks with stronger FUV irradiation. No clear relationships are detected between either CN or HCN and LyA or UV-H2 emission. This is attributed to the spatial stratification of the various molecular species, which span several vertical layers and radii across the inner and outer disk. We expect that future observations with JWST will build on this work by enabling more sensitive IR surveys than were possible with Spitzer.

[16]  arXiv:2002.09083 [pdf, other]
Title: Angular momentum-related probe of cold gas deficiencies
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Recent studies of neutral atomic hydrogen (HI) in nearby galaxies found that all field disk galaxies are HI saturated, in that they carry roughly as much HI as permitted before this gas becomes gravitationally unstable. By taking this HI saturation for granted, the atomic gas fraction $f_{\rm atm}$ of galactic disks can be predicted as a function of the stability parameter $q=j\sigma/(GM)$, where $M$ and $j$ are the baryonic mass and specific angular momentum of the disk and $\sigma$ is the HI velocity dispersion Obreschkow et al. 2016. The log-ratio $\Delta f_q$ between this predictor and the observed atomic fraction can be seen as a physically motivated `HI deficiency'. While field disk galaxies have $\Delta f_q \approx0$, objects subject to environmental removal of HI are expected to have $\Delta f_q>0$. Within this framework, we revisit the HI deficiencies of satellite galaxies in the Virgo cluster and in clusters of the EAGLE simulation. We find that observed and simulated cluster galaxies are HI deficient and that $\Delta f_q$ slightly increases when getting closer to the cluster centres. The $\Delta f_q$ values are similar to traditional HI deficiency estimators, but $\Delta f_q$ is more directly comparable between observations and simulations than morphology-based deficiency estimators. By tracking the simulated HI deficient cluster galaxies back in time, we confirm that $\Delta f_q\approx0$ until the galaxies first enter a halo with $M_{\rm halo}>10^{13} {\rm M_{\odot}}$, at which moment they quickly lose HI by environmental effects. Finally, we use the simulation to investigate the links between $\Delta f_q$ and quenching of star formation.

[17]  arXiv:2002.09121 [pdf, ps, other]
Title: ALMA CO Observations of the Host Galaxies of Long-duration Gamma-ray Bursts. I: Molecular Gas Scaling Relations
Comments: 26 pages, 12 figures, accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the results of CO observations toward 14 host galaxies of long-duration gamma-ray bursts (GRBs) at z = 0.1-2.5 by using the Atacama Large Millimeter/submillimeter Array. We successfully detected CO(3-2) or CO(4-3) emission in eight hosts (z = 0.3-2), which more than doubles the sample size of GRB hosts with CO detection. The derived molecular gas mass is $M_{\rm gas} = (0.2-6) \times 10^{10}$ $M_{\odot}$ assuming metallicity-dependent CO-to-H$_2$ conversion factors. By using the largest sample of GRB hosts with molecular gas estimates (25 in total, of which 14 are CO-detected) including results from the literature, we compared molecular gas properties with those of other star-forming galaxies (SFGs). The GRB hosts tend to have a higher molecular gas mass fraction ($\mu_{\rm gas}$) and a shorter gas depletion timescale ($t_{\rm depl}$) as compared with other SFGs at similar redshifts especially at $z \lesssim 1$. This could be a common property of GRB hosts or an effect introduced by the selection of targets which are typically above the main-sequence line. To eliminate the effect of selection bias, we analyzed $\mu_{\rm gas}$ and $t_{\rm depl}$ as a function of the distance from the main-sequence line ($\delta$MS). We find that the GRB hosts follow the same scaling relations as other SFGs, where $\mu_{\rm gas}$ increases and $t_{\rm depl}$ decreases with increasing $\delta {\rm MS}$. No molecular gas deficit is observed when compared to other SFGs of similar SFR and stellar mass. These findings suggest that the same star-formation mechanism is expected to be happening in GRB hosts as in other SFGs.

[18]  arXiv:2002.09122 [pdf, ps, other]
Title: Disk evolution of the M87's nucleus observed in 2008
Comments: 14 pages, 6 figures, accepted by Research in Astronomy and Astrophysics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

We report the discovery of year-scale X-ray variation in the nuclear region of the M87 by reanalyzing the 8 Chandra observations from 2007 to 2008. The X-ray spectra are fitted and decomposed into the disk and flaring components. This year-scale X-ray variability can be explained quite well by a simple clumpy accretion model. We conclude that the central super-massive black hole of the M87 was accreting a cloud of $\sim0.5$M$_\odot$ at that time.

[19]  arXiv:2002.09135 [pdf, other]
Title: A Relationship Between Stellar Age and Spot Coverage
Authors: Brett M. Morris
Comments: 21 pages, 11 figures, accepted in ApJ, software in review at JOSS this https URL
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

We investigate starspot distributions consistent with space-based photometry of F, G, and K stars in six stellar associations ranging in age from 10 Myr to 4 Gyr. We show that a simple light curve statistic called the "smoothed amplitude" is proportional to stellar age as $t^{-1/2}$, following a Skumanich-like spin-down relation. We marginalize over the unknown stellar inclinations by forward modeling the ensemble of light curves for direct comparison with the Kepler, K2 and TESS photometry. We sample the posterior distributions for spot coverage with Approximate Bayesian Computation. We find typical spot coverages in the range 1-10% which decrease with increasing stellar age. The spot coverage is proportional to $t^n$ where $n =-0.37 \pm 0.16$, also statistically consistent with a Skumanich-like $t^{-1/2}$ decay of starspot coverage with age. We apply two techniques to estimate the spot coverage of young exoplanet-hosting stars likely to be targeted for transmission spectroscopy with the James Webb Space Telescope, and estimate the bias in exoplanet radius measurements due to varying starspot coverage.

[20]  arXiv:2002.09149 [pdf, other]
Title: Poorly Studied Eclipsing Binaries in the Field of DO Dra: V0455 Dra and V0454 Dra
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We report an analysis of two poorly studied systems GSC 04396-00605 and GSC 04395-00485, which were recently named as V0455 Dra and V0454 Dra, respectively. For two eclipsing stars, the periods and epochs were significantly corrected using our extensive data. The phenomenological characteristics of the mean light curves were determined using the "New Algol Variable" (NAV) algorithm. The individual times of Maxima/Minima (ToM) were determined using the newly developed software MAVKA, which outputs the accurate parameters using the "asymptotic parabola" approximations. The light curves were approximated using the Wilson-Devinney model, the best fit parameters are listed. For both systems, the presence of the dark spot is justified, the parameters are estimated. Both systems classified to be overcontact binaries of EW type. The observations were obtained using the 1-m Korean telescope of the LOAO while monitoring the cataclysmic variable DO Dra within the "Inter-Longitude Astronomy" (ILA) project.

[21]  arXiv:2002.09173 [pdf, other]
Title: Mixed State Dynamics with Non-Local Interactions
Comments: 6 pages, 3 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics - Phenomenology (hep-ph); Quantum Physics (quant-ph)

The evolution of degenerate matter out of equilibrium is a topic of interest in fields such as condensed matter, nuclear and atomic physics, and increasingly cosmology, including inflaton physics prior to reheating. This follow-up paper extends the recent paper on the super-de Broglie dynamics of pure condensates of non-relativistic identical particles subject to non-local two-body interactions to the dynamics of mixed states. It is found that the two-body correlation function plays an increasingly dynamical role in these systems, driving the development of condensates and distributed phases alike. Examples of distribution and correlation evolution are presented, including instances of collapse, bound and unbound states, and phonons in the bulk. Potential applications are also discussed.

[22]  arXiv:2002.09198 [pdf, other]
Title: How "cold" are superthin discs ? An "MCMC" approach
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Superthin galaxies are a class of low surface brightness galaxies with strikingly high values of planar-to-vertical axes ratio $\rm(b/a> 10 - 20)$ with little or no bulge component, possibly indicating the presence of an ultra-cold stellar disc, the origin, and evolution of which is not well understood. Using the 2-component model of gravitationally-coupled stars and gas in the external force field of a dark matter halo and assumed to be in vertical hydrostatic equilibrium, we determine the vertical velocity dispersion of stars and gas as a function of galactocentric radius for a sample of five superthin galaxies (UGC 7321, IC 5249, FGC 1540, IC2233 and UGC711) using observed stellar and atomic hydrogen gas (HI) scaleheights as constraints, and employing the Markov Chain Monte Carlo (MCMC) method. The mass models for our sample galaxies, constructed using stellar photometry and HI 21cm radio-synthesis observations were already available in the literature. We find that the central vertical velocity dispersion for the stellar disc in the optical band varies between ${\sigma}_0$ $\sim$ $10.2 - 18.4 km/s$ and falls off with an exponential scale length of $2.6$ to $3.2 R_{D}$ where $R_{D}$ is the exponential stellar disc scale length. Interestingly, in the $3.6 \mu$m, the same, averaged over the two components of the stellar disc, varies between $5.9$ to $11.8 km/s$, mainly representative of the denser, thinner and smaller of the two-disc components. However, the dispersion of the more massive disc component varies between 15.9 - 24.7 with a scalelength of $\sim$ 2.2 $R_{D}$. Our calculated values of the N-component disc stability parameter $Q_{min}$ lies between 1.7 - 5.7, thus confirming the dynamic stability of our model. Further, our model results are consistent with AGAMA(Action-based Galaxy Modelling Architecture).

[23]  arXiv:2002.09204 [pdf, other]
Title: A more detailed look at Galactic magnetic field models: using free-free absorption in HII regions
Comments: 13 pages, 6 figures. Accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The observed interaction product of Cosmic Rays (CRs) and Galactic magnetic fields (GMF) is the Galactic synchrotron emission integrated over the line-of-sight (LOS). The GMF strength and morphology and the CR density can be probed by comparing this tracer to simulations using existing GMF models and CR density models. Our aim is to provide insight into these parameters by exploring and explaining the differences between simulations and observations of synchrotron intensity. At low radio frequencies HII regions become opaque due to free-free absorption. Using these HII regions we can measure the synchrotron intensity over a part of the LOS through the Galaxy. The measured intensity per unit path length, i.e. the emissitivity, for HII regions at different distances, will allow probing variation in synchrotron emission in the third dimension of distance. Using a number of existing GMF models in conjunction with the Galactic CR modeling code GALPROP we can simulate these synchrotron emissivities. We present an updated catalog of low-frequency absorption measurements of HII regions compiled from the literature. We report a simulated emissivity that shows a compatible trend for HII regions that are near to the observer. And we observe a systematically increasing synchrotron emissivity for HII regions that are far from the observer, which is not compatible with simulated values. Current GMF and CR density models cannot explain low-frequency absorption measurements. One possibility is that distances to all HII regions at the kinematic 'far' distance are wrong, though this is unlikely as it ignores all evidence in the literature. However, a detection bias due to the nature of this tracer requires us to keep in mind that certain sources may be missed in an observation. The other possibilities are an enhanced emissivity in the outer Galaxy or a diminished emissivity in the inner Galaxy.

[24]  arXiv:2002.09211 [pdf, ps, other]
Title: Detection and Classification of Astronomical Targets with Deep Neural Networks in Wide Field Small Aperture Telescopes
Comments: Submitted to AAS journal. The complete code can be downloaded from this https URL This code can be directly used to process images obtained by WFSATs. Images obtained by ordinary sky survey telescopes can also be processed with this code, however more annotated images are required to train the neural network
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Computer Vision and Pattern Recognition (cs.CV)

Wide field small aperture telescopes are widely used in optical transient observations. Detection and classification of astronomical targets are important steps during data post-processing stage. In this paper, we propose an astronomical targets detection and classification framework based on deep neural networks for images obtained by wide field small aperture telescopes. Our framework adopts the concept of the Faster R-CNN and we further propose to use a modified Resnet-50 as backbone network and a Feature Pyramid Network architecture in our framework. To improve the effectiveness of our framework and reduce requirements of large training set, we propose to use simulated images to train our framework at first and then modify weights of our framework with only a small amount of training data through transfer-learning. We have tested our framework with simulated and real observation data. Comparing with the traditional source detection and classification framework, our framework has better detection ability, particularly for dim astronomical targets. To unleash the transient detection ability of wide field small aperture telescopes, we further propose to install our framework in embedded devices to achieve real-time astronomical targets detection abilities.

[25]  arXiv:2002.09243 [pdf, other]
Title: VLTI-PIONIER imaging of the red supergiant V602 Carinae
Comments: 16 pages, 13 figures, accepted for publication in Astronomy and Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Context. Red supergiant stars possess surface features and extended molecular atmospheres. Photospheric convection may be a crucial factor of the levitation of the outer atmospheric layers. However, the mechanism responsible is still poorly understood. Aims. We image the stellar surface of V602 Carinae (V602 Car) to constrain the morphology and contrast of the surface features and of the extended atmospheric layers. Methods. We observed V602 Car with the Very Large Telescope Interferometer (VLTI) PIONIER instrument (1.53-1.78 $\mathrm{\mu}$m) between May and July 2016, and April and July 2019 with different telescope configurations. We compared the image reconstructions with 81 temporal snapshots of 3D radiative-hydrodynamics (RHD) CO$^5$BOLD simulations in terms of contrast and morphology, using the Structural Similarity Index. Results. The interferometric data are compatible with an overall spherical disk of angular diameter 4.4$\pm$0.2 mas, and an extended molecular layer. In 2016, the reconstructed image reveals a bright arc-like feature toward the northern rim of the photospheric surface. In 2019, an arc-like feature is seen at a different orientation and a new peak of emission is detected on the opposite side. The contrasts of the reconstructed surface images are 11%$\pm$2% and 9%$\pm$2% for 2016 and 2019, respectively. The morphology and contrast of the two images are consistent with 3D RHD simulations, within our achieved spatial resolution and dynamic range. The extended molecular layer contributes 10--13% of the total flux with an angular diameter of 6--8 mas. It is present but not clearly visible in the reconstructed images because it is close to the limits of the achieved dynamic range. The presence of the molecular layer is not reproduced by the 3D RHD simulations. Conclusions...

[26]  arXiv:2002.09251 [pdf, ps, other]
Title: Evidence for radio and X-ray auroral emissions from the magnetic B-type star \r{ho} Oph A
Comments: 20 pages, 13 figures; MNRAS minor revision
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We present new ATCA multi-wavelength radio measurements (range 2.1-21.2 GHz) of the early-type magnetic star \r{ho} Oph A, performed in March 2019 during 3 different observing sessions. These new ATCA observations evidence a clear rotational modulation of the stellar radio emission and the detection of coherent auroral radio emission from \r{ho} Oph A at 2.1 GHz. We collected high-resolution optical spectra of \r{ho} Oph A acquired by several instruments over a time span of about ten years. We also report new magnetic field measurements of \r{ho} Oph A that, together with the radio light curves and the temporal variation of the equivalent width of the HeI line ({\lambda}=5015 {\AA}), were used to constrain the rotation period and the stellar magnetic field geometry. The above results have been used to model the stellar radio emission, modelling that allowed us to constrain the physical condition of \r{ho} Oph A's magnetosphere. Past XMM measurements showed periodic X-ray pulses from \r{ho} Oph A. We correlate the X-ray light curve with the magnetic field geometry of \r{ho} Oph A. The already published XMM data have been re-analyzed showing that the X-ray spectra of \r{ho} Oph A are compatible with the presence of a non-thermal X-ray component. We discuss a scenario where the emission phenomena occurring at the extremes of the electromagnetic spectrum, radio and X-ray, are directly induced by the same plasma process. We interpret the observed X-ray and radio features of \r{ho} Oph A as having an auroral origin.

[27]  arXiv:2002.09255 [pdf, other]
Title: VMC J021140.41-735320.4 -- an extremely red L dwarf candidate member of the AB Doradus young moving group
Comments: 2 pages, 1 figure, published in RNAAS (abstract not included in original paper)
Journal-ref: 2020 RNAAS, 4, 20
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

We report the discovery of VMC J021140.41-735320.4, a faint ($J=19.9$ mag) and extremely red ($J-K_s=3.0$ mag, $W1-W2=0.45$ mag, $J-W2=4.7$ mag) high proper motion object in front of the Magellanic Bridge region. It is even redder in the near-infrared than the reddest L7 dwarfs ($J-K_s \gtrsim 2.8$ mag) found in the survey of Schneider et al. (2017) and its colours do also not match exactly those of other peculiar red L7.5 dwarfs. Therefore, we consider its photometric distance estimate of about 73 pc as uncertain. A preliminary combined proper motion and parallax solution involving 20 epochs from the Visible and Infrared Survey Telescope for Astronomy (VISTA) survey of the Magellanic Clouds (VMC), the VISTA hemisphere survey (VHS), and the Wide-field Infrared Survey Explorer (WISE) yields $\mu_{\alpha}\cos{\delta}=+74.3\pm3.4$ mas/yr, $\mu_{\delta}=+22.3\pm3.4$ mas/yr, and $\pi=21.0\pm7.1$ mas. Applying the BANYAN tool (this http URL) to these results we find a $\approx$68% membership probability of this object in the AB Doradus young moving group (YMG). With its trignometric distance of $\approx$48 pc, VMC J021140.41-735320.4 has a similar absolute magnitude of $M_{K_s}\approx13.4$ mag as the planetary mass companion of another AB Doradus YMG member candidate, 2MASS J22362452+4751425. Follow-up classification spectroscopy and astrometric monitoring are recommended.

[28]  arXiv:2002.09257 [pdf, other]
Title: Gas fractions and depletion times in galaxies with different degrees of interaction
Comments: Accepted for publication in A&A (February 21, 2020). 6 pages, 5 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the atomic gas content and the central stellar mass concentration for a sample of almost 1500 nearby galaxies to investigate the nature of starbursts and the influence of galaxy-galaxy interactions on star formation. We use the catalogue on interacting and merging galaxies in the S$^4$G survey of Knapen et al. (2014) along with archival HI gas masses, stellar masses ($M_{\ast}$), and SFRs (from IRAS far-IR fluxes), and calculate depletion times ($\tau$) and gas fractions. We trace the central stellar mass concentration from the inner slope of the stellar component of the rotation curves, $d_{\rm R}v_{\ast}(0)$. Starbursts - defined as galaxies with a factor $>4$ enhanced SFR relative to a control sample ($\pm 0.2$ dex in stellar mass, $\pm 1$ in $T$-type, non-interacting) - are mainly early-type ($T\lesssim 5$) massive spiral galaxies ($M_{\ast}\gtrsim 10^{10}M_{\odot}$), not necessarily interacting. For a given stellar mass bin, starbursts are characterised by lower gas depletion times, similar gas fractions, and larger central stellar mass concentrations than non-starburst galaxies. The global distributions of gas fraction and gas depletion time are not statistically different for interacting and non-interacting galaxies. However, in the case of currently merging galaxies, the median gas depletion time is a factor of $0.4 \pm 0.2$ that of control sample galaxies, and their star formation rates are a factor of $1.9 \pm 0.5$ enhanced, even though the median gas fraction is similar. Starbursts present long-lasting star formation in the circumnuclear regions that causes an enhancement of the central stellar density at $z\approx0$ in both interacting and non-interacting systems. Starbursts have low gas depletion timescales, yet similar gas fractions as normal main-sequence galaxies. Galaxy mergers cause a moderate enhancement of the star formation efficiency (Abridged).

[29]  arXiv:2002.09271 [pdf, other]
Title: Fly-by encounters between two planetary systems II: Exploring the interactions of diverse planetary system architectures
Comments: submitted to MNRAS, revised as per referee comments
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Planetary systems formed in clusters may be subject to stellar encounter flybys. Here we create a diverse range of representative planetary systems with different orbital scales and planets' masses and examine encounters between them in a typical open cluster. We first explore the close-in multi-super earth systems $\lesssim0.1$ au. They are resistant to flybys in that only ones inside a few au can destabilise a planet or break the resonance between such planets. But these systems may capture giant planets onto wide orbits from the intruding star during distant flybys. If so, the original close-in small planets' orbits may be tilted together through Kozai--Lidov mechanism, forming a "cold" system that is significantly inclined against the equator of the central host. Moving to the intermediately-placed planets around solar-like stars, we find that the planets' mass gradient governs the systems' long-term evolution post-encounter: more massive planets have better chances to survive. Also, a system's angular momentum deficit, a quantity describing how eccentric/inclined the orbits are, measured immediately after the encounter, closely relates to the longevity of the systems -- whether or not and when the systems turn unstable in the ensuing evolution millions of years post-encounter. We compare the orbits of the surviving planets in the unstable systems through (1) the immediate consequence of the stellar fly or (2) internal interplanetary scattering long post-encounter and find that those for the former are systematically colder. Finally, we show that massive wide-orbit multi-planet systems like that of HR 8799 can be easily disrupted and encounters at a few hundreds of au suffice.

[30]  arXiv:2002.09293 [pdf, other]
Title: Cosmological parameter analyses using transversal BAO data
Comments: 15 pages, 10 figures, 4 tables. Comments are welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

Current data analyses combine diverse cosmological probes to break degeneracy between cosmological parameters using, for instance, the data from Type IA supernova data or from Baryon Acoustic Oscillations (BAO). Regarding the use of the BAO data, this can lead to biased inferences of the cosmological parameters in study because the comoving BAO sound horizon at drag epoch, $r_{\rm drag}$, used to quantify the BAO measurements $H(z)$ and $D_{A}(z)$, is inferred from a combination of cosmic microwave background (CMB) data and a theoretical model, as WMAP and Planck collaborations did. One can avoid possibly biased analyses combining CMB data in conjunction with a set of 15 measurements of the transversal BAO scale, considered cosmological model-independent to explore, via Monte Carlo Markov chains, the parametric space of some cosmological models. We investigate how much Planck CMB data in combination with transversal BAO measurements can constraints the minimum $\Lambda$CDM model, and extensions including additional parameters as $r_{\rm drag}$, neutrinos mass scale $M_{\nu}$, and the possibility for a dynamical dark energy model. Assuming the $\Lambda$CDM cosmology, we find $H_0 = 69.23 \pm 0.50$ km s${}^{-1}$ Mpc${}^{-1}$, $M_{\nu} < 0.11$ eV and $r_{\rm drag} = 147.59 \pm 0.26$ Mpc from Planck + transversal BAO data. When assuming a dynamical dark energy cosmology, we find that the inclusion of the BAO data can indeed break the degeneracy of the dark energy free parameters, improving the constraints on the full parameter space significantly. We note that the model is compatible with local measurements of $H_0$ and there is no tension on $H_0$ estimates. Also, we discuss the results from a joint analysis with the latest local $H_0$ measurement. Finally, we perform a model-independent analysis for the deceleration parameter $q(z)$ from our compilation of the transversal BAO data.

[31]  arXiv:2002.09310 [pdf]
Title: On a method for the analysis of compulsive phase mixing and its application in cosmogony of galaxy superclusters
Subjects: Astrophysics of Galaxies (astro-ph.GA); Chaotic Dynamics (nlin.CD)

In this paper, we study the strong non-stationary stochastic processes that take place in the phase space of self-gravitating systems at the initial non-stationary stage of their evolution. The numerical calculations of the compulsive phase mixing process were carried out based on the model of chaotic impacts, according to which the initially selected phase volume experiences random impacts of a different and complex nature.

[32]  arXiv:2002.09311 [pdf, other]
Title: A long period (P = 61.8-d) M5V dwarf eclipsing a Sun-like star from TESS and NGTS
Comments: 8 pages, 5 figures, 3 tables. Submitted to MNRAS. arXiv admin note: substantial text overlap with arXiv:1910.05282
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)

The Transiting Exoplanet Survey Satellite (TESS) has produced a large number of single transit event candidates which are being monitored by the Next Generation Transit Survey (NGTS). We observed a second epoch for the TIC-231005575 system (Tmag = 12.06, Teff = 5500 +- 85 K) with NGTS and a third epoch with Las Cumbres Observatory's (LCO) telescope in South Africa to constrain the orbital period (P = 61.777 d). Subsequent radial velocity measurements with CORALIE revealed the transiting object has a mass of M2 = 0.128 +- 0.003 M$_\odot$, indicating the system is a G-M binary. The radius of the secondary is R2 = 0.154 +- 0.008 R$_\odot$ and is consistent with models of stellar evolution to better than 1-$\sigma$.

[33]  arXiv:2002.09328 [pdf, other]
Title: The AMUSING++ Nearby Galaxy Compilation: I. Full Sample Characterization and Galactic--Scale Outflows Selection
Comments: 49 pages, 20 figures, accepted for publishing in AJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present here AMUSING\textrm{++}; the largest compilation of nearby galaxies observed with the MUSE integral field spectrograph so far. This collection consists of 635 galaxies from different MUSE projects covering the redshift interval $0.0002<z<0.1$. The sample and its main properties are characterized and described in here. It includes galaxies of almost all morphological types, with a good coverage in the color-magnitude diagram, within the stellar mass range between 10$^8$ to 10$^{12}$M$_\odot$, and with properties resembling those of a diameter-selected sample. The AMUSING++ sample is therefore suitable to study, with unprecendent detail, the properties of nearby galaxies at global and local scales, providing us with more than 50 million individual spectra. We use this compilation to investigate the presence of galactic outflows. We exploit the use of combined emission-line images to explore the shape of the different ionized components and the distribution along classical diagnostic diagrams to disentangle the different ionizing sources across the optical extension of each galaxy. We use the cross correlation function to estimate the level of symmetry of the emission lines as an indication of the presence of shocks and/or active galactic nuclei. We uncovered a total of 54 outflows, comprising $\sim$8\% of the sample. A large number of the discovered outflows correspond to those driven by active galactic nuclei ($\sim$60\%), suggesting some bias in the selection of our sample. No clear evidence was found that outflow host galaxies are highly star-forming, and outflows appear to be found within all galaxies around the star formation sequence.

[34]  arXiv:2002.09331 [pdf, ps, other]
Title: Extending Gaia DR2 with HST narrow-field astrometry. II. Refining the method on WISE J163940.83-684738.6
Authors: L. R. Bedin (1), C. Fontanive (2,3) ((1) INAF-OAPD, (2) Inst. for Astronomy and (3) Centre for Space and Habitability, Univ. of Bern)
Comments: 10 pages, 3 tables, 3 figures (fig.1 at low resolution). Accepted for publication in MNRAS on 2020 February 21
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

In the second paper of this series we perfected our method of linking high precision Hubble Space Telescope astrometry to the high-accuracy Gaia DR2 absolute reference system to overcome the limitations of relative astrometry with narrow-field cameras. Our test case here is the Y brown dwarf WISE J163940.83-684738.6, observed at different epochs spread over a 6-yr time baseline with the Infra-Red channel of the Wide Field Camera 3. We derived significantly improved astrometric parameters compared to previous determinations, finding: (mu_RAcosDc,mu_DC,parallax) = (577.21+/-0.24mas/yr,-3108.39+/-0.27mas/yr,210.4+/-1.8mas). In particular, our derived absolute parallax corresponds to a distance of 4.75+/-0.05pc for the faint ultracool dwarf.

[35]  arXiv:2002.09360 [pdf, other]
Title: Radio morphology-accretion mode link in FRII low-excitation radio galaxies
Authors: D. Macconi (DIFA Bologna, INAF-OAS Bologna), E. Torresi, P. Grandi (INAF-OAS Bologna), B. Boccardi (MPIFR), C. Vignali (DIFA Bologna, INAF-OAS Bologna)
Comments: 13 pages, 7 figures, Accepted for publication in MNRAS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

Fanaroff-Riley II low-excitation radio galaxies (FRII-LERGs) are characterized by weak nuclear excitation on pc-scales and by properties typical of powerful FRIIs (defined as high-excitation, hereafter HERGs/BLRGs) on kp-scales. Since a link between the accretion properties and the power of the produced jets is expected both from theory and observations, their nature is still debated. In this work we investigate the X-ray properties of a complete sample of 19 FRII-LERGs belonging to the 3CR catalog, exploiting Chandra and XMM-Newton archival data. We also analyze 32 FRII-HERGs/BLRGs with Chandra data as a control sample. We compared FRII-LERG and FRII-HERG/BLRG X-ray properties and optical data available in literature to obtain a wide outlook of their behavior. The low accretion rate estimates for FRII-LERGs, from both X-ray and optical bands, allow us to firmly reject the hypothesis for that they are the highly obscured counterpart of powerful FRII-HERGs/BLRGs. Therefore, at least two hypothesis can be invoked to explain the FRII-LERGs nature: (i) they are evolving from classical FRIIs because of the depletion of accreting cold gas in the nuclear region, while the extended radio emission is the heritage of a past efficiently accreting activity; (ii) they are an intrinsically distinct class of objects with respect to classical FRIs/FRIIs. Surprisingly, in this direction a correlation between accretion rates and environmental richness is found in our sample. The richer the environment, the more inefficient is the accretion. In this framework, the FRII-LERGs are intermediate between FRIs and FRII-HERGs/BLRGs both in terms of accretion rate and environment.

[36]  arXiv:2002.09367 [pdf, other]
Title: ODUSSEAS: A machine learning tool to derive effective temperature and metallicity for M dwarf stars
Comments: 16 pages, 14 figures, Accepted by A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Aims. The derivation of spectroscopic parameters for M dwarf stars is very important in the fields of stellar and exoplanet characterization. The goal of this work is the creation of an automatic computational tool, able to derive quickly and reliably the T$_{\mathrm{eff}}$ and [Fe/H] of M dwarfs by using their optical spectra, that can be obtained by different spectrographs with different resolutions.
Methods. ODUSSEAS (Observing Dwarfs Using Stellar Spectroscopic Energy-Absorption Shapes) is based on the measurement of the pseudo equivalent widths for more than 4000 stellar absorption lines and on the use of the machine learning Python package "scikit-learn" for predicting the stellar parameters.
Results. We show that our tool is able to derive parameters accurately and with high precision, having precision errors of ~30 K for T$_{\mathrm{eff}}$ and ~0.04 dex for [Fe/H]. The results are consistent for spectra with resolutions between 48000 and 115000 and SNR above 20.

[37]  arXiv:2002.09392 [pdf]
Title: Recommendations for optimizing rapid ultraviolet HST observations of gravitational wave optical counterparts
Comments: 8 pages, 2 figures
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

This document presentes general guidelines to investigators proposing ultra-rapid target of opportunity (ToO) observations with the Hubble Space Telescope (HST). Establishing clear plans in advance and communicating with STScI staff, particularly the Program Coordinator, are crucial to minimising the time between triggering a ToO and executing the observations.

[38]  arXiv:2002.09395 [pdf, other]
Title: The kilonova of GW190425-like events
Comments: 7 pages, 5 figures, submitted to A&A
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

GW190425 is the newly discovered compact object binary coalescence consistent with a neutron star-neutron star merger, with a chirp mass of $1.44\pm0.02M_\odot$. No electromagnetic counterpart is firmly associated with this event, due to the poorly informative sky localisation and larger distance, compared to GW/GRB170817. The detection of the gravitational wave signal alone can not rule out the presence of a black hole in the binary. In this case, the system would host a neutron star and a very light stellar black hole, with a mass close to the maximum value for neutron stars. We show that the possible presence of such a black hole in GW190425 would produce a brighter kilonova emission with respect to the double neutron star case. Therefore in GW190425-like events more precisely localised, the identification of a kilonova could help distinguishing the nature of the merging system. The chirp mass is a key parameter when joint gravitational and electromagnetic observations are possible. The knowledge of its value could help conducting strategic electromagnetic follow-up campaigns that would enhance the probability to identify the nature of the binary and the host galaxy. For GW190425-like events, we construct kilonova light curve models, for both double neutron star and black hole-neutron star binaries, considering two equations of state both consistent with the observations of GW170817 and GW190425, and including black hole spin effects. We show that among the candidate counterparts of GW190425, all classified as supernovae, our models would exclude two events through their early $r$-band flux evolution. This illustrates that combining the chirp mass and luminosity distance information (provided by the GW signal) with a library of kilonovae light curves can help the electromagnetic follow up campaign, particularly for events with a poor sky localization.

[39]  arXiv:2002.09407 [pdf, other]
Title: Dynamic Normalization for Compact Binary Coalescence Searches in Non-Stationary Noise
Authors: S. Mozzon (1), L. K. Nuttall (1), A. Lundgren (1), S. Kumar (2 and 3), A. H. Nitz (2 and 3), T. Dent (4) ((1) University of Portsmouth, Portsmouth, United Kingdom, (2) Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Hannover, Germany, (3) Leibniz Universität Hannover, Hannover, Germany, (4) Instituto Galego de Física de Altas Enerxías, Universidade de Santiago de Compostela, Santiago de Compostela, Spain)
Comments: 11 pages, 2 figures. Submitted to Classical and Quantum Gravity
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The output of gravitational-wave interferometers, such as LIGO and Virgo, can be highly non-stationary. Broadband detector noise can affect the detector sensitivity on the order of tens of seconds. Gravitational-wave transient searches, such as those for colliding black holes, estimate this noise in order to identify gravitational-wave events. During times of non-stationarity we see a higher rate of false events being reported. To accurately separate signal from noise, it is imperative to incorporate the changing detector state into gravitational-wave searches. We develop a new statistic which estimates the variation of the interferometric detector noise. We use this statistic to re-rank candidate events identified during LIGO-Virgo's second observing run by the PyCBC search pipeline. This results in a 7% improvement in the sensitivity volume for low mass binaries, particularly binary neutron stars mergers.

[40]  arXiv:2002.09411 [pdf, other]
Title: Multi-scale simulations of particle acceleration in astrophysical systems
Comments: 202 pages, 43 figures, to be published in the Living Reviews of Computational Astrophysics
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

This review aims at providing an up-to-date status and a general introduction to the subject of the numerical study of energetic particle acceleration and transport in turbulent astrophysical flows. The subject is also complemented by a short overview of recent progresses obtained in the domain of laser plasma experiments. We review the main physical processes at the heart of the production of a non-thermal distribution in both Newtonian and relativistic astrophysical flows, namely the first and second order Fermi acceleration processes. We also discuss shock drift and surfing acceleration, two processes important in the context of particle injection in shock acceleration. We analyze with some details the particle-in-cell (PIC) approach used to describe particle kinetics. We review the main results obtained with PIC simulations in the recent years concerning particle acceleration at shocks and in reconnection events. The review discusses the solution of Fokker-Planck problems with application to the study of particle acceleration at shocks but also in hot coronal plasmas surrounding compact objects. We continue by considering large scale physics. We describe recent developments in magnetohydrodynamic (MHD) simulations. We give a special emphasize on the way energetic particle dynamics can be coupled to MHD solutions either using a multi-fluid calculation or directly coupling kinetic and fluid calculations. This aspect is mandatory to investigate the acceleration of particles in the deep relativistic regimes to explain the highest Cosmic Ray energies.

[41]  arXiv:2002.09431 [pdf, other]
Title: Clusters of Galaxies Masquerading as X-Ray Quasars
Comments: PDF, as published in Astrophysical Journal. 4 figures, 4 tables
Journal-ref: 2020, Astrophysical Journal, 889, 121
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Inspired by the discovery of the Phoenix cluster by the South Pole Telescope team, we initiated a search for other massive clusters of galaxies missing from the standard X-ray catalogs. We began by identifying 25 cluster candidates not included in the Meta-Catalog of X-ray Clusters of galaxies cluster compilation through cross-identification of the central galaxies of optically identified clusters in the Sloan Digital Sky Survey GMBCG catalog with bright X-ray sources in the ROSAT Bright Source Catalog. Those candidates were mostly unidentified or previously classified as X-ray active galactic nucleus (AGN). We analyzed brief Chandra X-ray Observatory observations of 14 of these X-ray sources and found that eight are X-ray luminous clusters of galaxies, only one showing evidence for a central X-ray point source. The remaining six candidates turned out to be point-source dominated, with faint detections or upper limits on any extended emission. We were not able to rule out the presence of extended X-ray emission from any of the point sources. The levels of extended emission around the six point sources are consistent with expectations based on optical richness, but could also be contaminated by scattered X-ray light from the central point source or extended nonthermal emission from possible radio lobes. We characterize the extended components of each of the well-detected cluster sources, finding that six of the eight X-ray clusters are consistent with being compact cool-core clusters. One of the newly identified low-luminosity X-ray clusters may have had an X-ray-luminous AGN 20 yr prior to the recent Chandra observations, based on the 4{\sigma} difference between its Chandra and ROSAT fluxes.

[42]  arXiv:2002.09439 [pdf, other]
Title: Tearing and related field distortions in deep-depletion CCDs
Comments: 11 pages, proceeding of ISPA2018
Journal-ref: J. Astron. Telesc. Instrum. Syst. 5(4), 041505 (2019)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Tearing patterns affecting flat field frames in CCDs are a visually striking obstacle to performing Pixel Response Non-Uniformity corrections. These patterns can be explained by lateral field distortions, caused by the non-uniform distribution of holes in the channel stops between sensor columns. Over the course of LSST camera development, a number of practical fixes have been suggested to get rid of tearing. But applying these fixes to our 16-channel Teledyne-e2v sensors leaves at best a distortion pattern at the vertical edges of every segment. Our working hypothesis is that the origin of the tearing is the parallel clocking itself, which moves the holes that are present in the channel stops regions. The efficiency of these transfers depends strongly on the details of the clocking operations, resulting in the observed variety of distortion patterns. Removal of most of the distortion patterns can therefore be achieved by executing a purge operation, which flattens back the hole distribution in the channel stops, immediately before acquiring a frame. A more effective solution is to switch all clocking operations to use a bipolar voltage set.

[43]  arXiv:2002.09442 [pdf, other]
Title: 3He-rich solar energetic particles: Solar sources
Authors: R. Bucik
Comments: accepted for publication in Space Sci Rev
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)

3He-rich solar energetic particles (SEPs), showing up to a 10,000-fold abundance enhancement of rare elements like 3He or ultra-heavy nuclei, have been a puzzle for more than 50 years. One reason for the current lack of understanding of 3He-rich SEPs is the difficulty resolving the source regions of these commonly occurring events. Since their discovery, there has been strong evidence that 3He-rich SEP production is associated with flares on the Sun. Anomalous abundances of 3He-rich SEPs have been attributed to a unique acceleration mechanism that must routinely operate at flare sites. Flares associated with 3He-rich SEPs have been often observed in jet-like forms indicating an acceleration in magnetic reconnection involving field lines open to interplanetary space. Owing to a fleet of spacecraft around the Sun, providing a greatly improved resolution of solar imaging observations, 3He-rich SEP sources are now explored in unprecedented detail. This paper outlines the current understanding of 3He-rich SEPs, mainly focusing on their solar sources.

[44]  arXiv:2002.09468 [pdf, other]
Title: Solar Contamination in Extreme Precision Radial Velocity Measurements: Deleterious Effects and Prospects for Mitigation
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Solar contamination, due to moonlight and atmospheric scattering of sunlight, can cause systematic errors in stellar radial velocity (RV) measurements that significantly detract from the ~10cm/s sensitivity required for the detection and characterization of terrestrial exoplanets in or near Habitable Zones of Sun-like stars. The addition of low-level spectral contamination at variable effective velocity offsets introduces systematic noise when measuring velocities using classical mask-based or template-based cross-correlation techniques. Here we present simulations estimating the range of RV measurement error induced by uncorrected scattered sunlight contamination. We explore potential correction techniques, using both simultaneous spectrometer sky fibers and broadband imaging via coherent fiber imaging bundles, that could reliably reduce this source of error to below the photon-noise limit of typical stellar observations. We discuss the limitations of these simulations, the underlying assumptions, and mitigation mechanisms. We also present and discuss the components designed and built into the NEID precision RV instrument for the WIYN 3.5m telescope, to serve as an ongoing resource for the community to explore and evaluate correction techniques. We emphasize that while "bright time" has been traditionally adequate for RV science, the goal of 10cm/s precision on the most interesting exoplanetary systems may necessitate access to darker skies for these next-generation instruments.

Cross-lists for Mon, 24 Feb 20

[45]  arXiv:2002.09004 (cross-list from physics.flu-dyn) [pdf, other]
Title: Stability and Solution of the Time-Dependent Bondi-Parker Flow
Authors: Eric Keto
Comments: To be published in MNRAS
Subjects: Fluid Dynamics (physics.flu-dyn); Solar and Stellar Astrophysics (astro-ph.SR)

Bondi (1952) and Parker (1958} derived a steady-state solution for Bernouilli's equation in spherical symmetry around a point mass for two cases, respectively, an inward accretion flow and an outward wind. Left unanswered were the stability of the steady-state solution, the solution itself of time-dependent flows, whether the time-dependent flows would evolve to the steady-state, and under what conditions a transonic flow would develop. In a Hamiltonian description, we find that the steady state solution is equivalent to the Lagrangian implying that time-dependent flows evolve to the steady state. We find that the second variation is definite in sign for isothermal and adiabatic flows, implying at least linear stability. We solve the partial differential equation for the time-dependent flow as an initial-value problem and find that a transonic flow develops under a wide range of realistic initial conditions. We present some examples of time-dependent solutions.

[46]  arXiv:2002.09144 (cross-list from hep-ph) [pdf, other]
Title: Resonant instability of axionic dark matter clumps
Authors: Z. Wang, L. Shao, L.-X. Li
Comments: 25 pages, 5 figures, uses jcappub.sty
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Axion is a popular candidate for dark matter particles. Axionic dark matter may form Bose-Einstein condensate and may be gravitationally bound to form axion clumps. Under the presence of electromagnetic waves with frequency $\omega=m_{a}/2$, where $m_{a}$ is the axion mass, a resonant enhancement may occur, causing an instability of the axion clumps. With analytical and numerical approaches, we study the resonant instability of axionic dark matter clumps with infinite homogeneous mass distribution, as well as distribution with a finite boundary. After taking realistic astrophysical environments into consideration, including gravitational redshift and plasma effects, we obtain an instability region in the axion density-clump size parameter space with given mass and coupling of axions. In particular, we show that, for axion clumps formed by the QCD axions in equilibrium, no resonant instability will occur.

[47]  arXiv:2002.09226 (cross-list from gr-qc) [pdf, other]
Title: Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object
Comments: 21 pages, 20 figures, submitted to A&A
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

Context. The Event Horizon Telescope (EHT) collaboration recently obtained first images of the surroundings of the supermassive compact object M87* at the center of the galaxy M87. Aims. We want to develop a simple analytic disk model for the accretion flow of M87*. Compared to general-relativistic magnetohydrodynamic (GRMHD) models, it has the advantage of being independent of the turbulent character of the flow, and controlled by only few easy-to-interpret, physically meaningful parameters. We want to use this model to predict the image of M87* assuming that it is either a Kerr black hole, or an alternative compact object. Methods. We compute the synchrotron emission from the disk model and propagate the resulting light rays to the far-away observer by means of relativistic ray tracing. Such computations are performed assuming different spacetimes (Kerr, Minkowski, non-rotating ultracompact star, rotating boson star or Lamy spinning wormhole). We perform numerical fits of these models to the EHT data. Results. We discuss the highly-lensed features of Kerr images and show that they are intrinsically linked to the accretion-flow properties, and not only to gravitation. This fact is illustrated by the notion of secondary ring that we introduce. Our model of spinning Kerr black hole predicts mass and orientation consistent with the EHT interpretation. The non-Kerr images result in similar quality of the numerical fits and may appear very similar to Kerr images, once blurred to the EHT resolution. This implies that a strong test of the Kerr spacetime may be out of reach with the current data. We notice that future developments of the EHT could alter this situation. Conclusions. Our results show the importance of studying alternatives to the Kerr spacetime in order to be able to test the Kerr paradigm unambiguously.

[48]  arXiv:2002.09429 (cross-list from gr-qc) [pdf, other]
Title: Utilizing aLIGO Glitch Classifications to Validate Gravitational-Wave Candidates
Comments: 16 pages, 6 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Advanced LIGO data contains numerous noise transients, or "glitches", that have been shown to reduce the sensitivity of matched filter searches for gravitational waves from compact binaries by increasing the rate at which random coincidences occur. The presence of these transients has precipitated extensive work to establish that observed gravitational wave events are astrophysical in nature. We discuss the response of the PyCBC search for gravitational waves from stellar mass binaries to various common glitches that were observed during Advanced LIGO's first and second observing runs. We show how these transients can mimic waveforms from compact binary coalescences and quantify the likelihood that a given class of glitches will create a trigger in the search pipeline. We explore the specific waveform parameters that are most similar to different glitch classes and demonstrate how knowledge of these similarities can be used when evaluating the significance of gravitational-wave candidates.

[49]  arXiv:2002.09454 (cross-list from physics.space-ph) [pdf, other]
Title: On the Interaction of Galactic Cosmic Rays with Heliospheric Shocks During Forbush Decreases
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)

Forbush decreases (FDs) are depletions in the galactic cosmic ray (GCR) count rate that last typically for about a week and can be caused by coronal mass ejections (CMEs) or corotating interacting regions (CIRs). Fast CMEs that drive shocks cause large FDs that often show a two-step decrease where the first step is attributed to the shock/sheath region, while the second step is attributed to the closed magnetic structure. Since the difference in size of shock and sheath region is significant, and since there are observed effects that can be related to shocks and not necessarily to the sheath region we expect that the physical mechanisms governing the interaction with GCRs in these two regions are different. We therefore aim to analyse interaction of GCRs with heliospheric shocks only. We approximate the shock by a structure where the magnetic field linearly changes with position within this structure. We assume protons of different energy, different pitch angle and different incoming direction. We also vary the shock parameters such as the magnetic field strength and orientation, as well as the shock thickness. The results demonstrate that protons with higher energies are less likely to be reflected. Also, thicker shocks and shocks with stronger field reflect protons more efficiently.

Replacements for Mon, 24 Feb 20

[50]  arXiv:1806.10436 (replaced) [pdf, other]
Title: Numerical treatment of the nonconservative product in a multiscale fluid model for plasmas in thermal nonequilibrium: application to solar physics
Authors: Quentin Wargnier (CMAP), Sylvain Faure (LM-Orsay), Benjamin Graille (LM-Orsay), Thierry Magin (VKI), Marc Massot (CMAP)
Subjects: Numerical Analysis (math.NA); Solar and Stellar Astrophysics (astro-ph.SR); Analysis of PDEs (math.AP); Classical Physics (physics.class-ph); Plasma Physics (physics.plasm-ph)
[51]  arXiv:1807.10593 (replaced) [pdf, other]
Title: Using all-sky differential photometry to investigate how nocturnal clouds darken the night sky in rural areas
Comments: 17 pages, 6 figures
Journal-ref: Sci Rep 9, 1391 (2019)
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Other Quantitative Biology (q-bio.OT)
[52]  arXiv:1811.00022 (replaced) [pdf, other]
Title: Roll of the Dice: A Stochastically Sampled IMF Alters the Stellar Content of Simulated Dwarf Galaxies
Comments: 14 pages, 11 figures, Updated to reflect accepted version, MNRAS
Journal-ref: Monthly Notices of the Royal Astronomical Society, 2020, 492, 8-21
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[53]  arXiv:1906.11921 (replaced) [pdf, other]
Title: Simulating the Spatial Distribution and Kinematics of Globular Clusters within Galaxy Clusters in Illustris
Comments: 13 pages, 10 figures, accepted in MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[54]  arXiv:1907.06966 (replaced) [pdf, other]
Title: Acoustic wave generation in collapsing massive stars with convective shells
Comments: Revised version. 17 pages, 8 figures, 1 table. Accepted for publication in MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Fluid Dynamics (physics.flu-dyn)
[55]  arXiv:1908.03151 (replaced) [pdf, other]
Title: Real-Time Detection of Gravitational Waves from Binary Neutron Stars using Artificial Neural Networks
Authors: Plamen G. Krastev (Harvard University)
Comments: 6 pages, 4 figures, 1 table. Accepted for publication in Physics Letters B
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
[56]  arXiv:1908.10367 (replaced) [pdf, other]
Title: Thermal Instability of Halo Gas Heated by Streaming Cosmic Rays
Comments: Accepted for publication in MNRAS; 18 Pages, 7 Figures. Note the modified sections on the impact of CR diffusion
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
[57]  arXiv:1909.04072 (replaced) [pdf, other]
Title: Signatures of Mirror Stars
Comments: 41 pages, 8 figures, 2 tables
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
[58]  arXiv:1909.10523 (replaced) [pdf, other]
Title: Rapid Transients Originating from Thermonuclear Explosions in Helium White Dwarf Tidal Disruption Events
Comments: 9 pages, 5 figures, published in ApJL
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[59]  arXiv:1910.11358 (replaced) [pdf, ps, other]
Title: The Origin of Binary Black Holes Mergers
Authors: Zoe Piran, Tsvi Piran
Comments: Accepted for publication in ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[60]  arXiv:1911.00276 (replaced) [pdf, other]
Title: Relativistic hybrid stars with sequential first-order phase transitions and heavy-baryon envelopes
Comments: 11 pages, 9 figures, 5 tables; ReVTex 4
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
[61]  arXiv:1911.05575 (replaced) [pdf, other]
Title: The dust effects on galaxy scaling relations
Comments: 12 pages, 7 figures, and 16 additional Appendix pages. Accepted for publication in MNRAS (February 12)
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[62]  arXiv:1911.06328 (replaced) [pdf, other]
Title: Sound-Wave Instabilities in Dilute Plasmas with Cosmic Rays: Implications for Cosmic-Ray Confinement and the Perseus X-ray Ripples
Comments: Accepted for publication in MNRAS; 14 Pages, 7 Figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
[63]  arXiv:1911.08493 (replaced) [pdf, other]
[64]  arXiv:1912.04732 (replaced) [pdf, other]
Title: Charge Constraints of Macroscopic Dark Matter
Comments: 14 pages, 8 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[65]  arXiv:1912.09374 (replaced) [pdf, other]
Title: Explaining the cuspy dark matter halo by Landau-Ginzburg theory
Authors: Dong-Biao Kang
Comments: 5 pages, 2 figures. Comments are welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); Statistical Mechanics (cond-mat.stat-mech)
[66]  arXiv:1912.09474 (replaced) [pdf, other]
Title: Physics of Eclipsing Binaries. IV. The impact of interstellar extinction on the light curves of eclipsing binaries
Comments: 10 pages, 5 figures. Accepted for publication in ApJS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
[67]  arXiv:1912.10792 (replaced) [pdf]
Title: A compact multi-planet system around a bright nearby star from the Dispersed Matter Planet Project
Comments: Accepted for publication by Nature Astronomy on 12th November 2019 (Main article, Methods and Supplementary Information; 24 pages, 10 figures, 3 tables)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[68]  arXiv:1912.12670 (replaced) [pdf, ps, other]
Title: New application of the Killing vector field formalism: Modified periodic potential and two-level profiles of the axionic dark matter distribution
Comments: 12 pages, 5 figures, replaced with revised version published in EPJC
Journal-ref: Eur. Phys. J. C (2020) 80:145
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Theory (hep-th)
[69]  arXiv:1912.12690 (replaced) [pdf, other]
Title: The Splash without a merger
Comments: Accepted for publication in ApJL
Subjects: Astrophysics of Galaxies (astro-ph.GA)
[70]  arXiv:2001.05967 (replaced) [pdf, other]
Title: Delay Time Distributions of Type Ia Supernovae From Galaxy and Cosmic Star Formation Histories
Comments: 20 pages, including 14 figures
Journal-ref: The Astrophysical Journal, 2020, 890, 2
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)
[71]  arXiv:2002.02941 (replaced) [pdf, ps, other]
Title: Swampland, Trans-Planckian Censorship and Fine-Tuning Problem for Inflation: Tunnelling Wavefunction to the Rescue
Comments: 14 pages, comments welcome; v2: references added
Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
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