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Astrophysics

New submissions

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New submissions for Fri, 31 Jan 20

[1]  arXiv:2001.11028 [pdf, other]
Title: The Lunar Lander Neutron and Dosimetry (LND) Experiment on Chang'E 4
Comments: 38 pages, submitted to Space Science Reviews
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Chang'E 4 is the first mission to the far side of the Moon and consists of a lander, a rover, and a relay spacecraft. Lander and rover were launched at 18:23 UTC on December 7, 2018 and landed in the von K\'arm\'an crater at 02:26 UTC on January 3, 2019. Here we describe the Lunar Lander Neutron \& Dosimetry experiment (LND) which is part of the Chang'E 4 Lander scientific payload. Its chief scientific goal is to obtain first active dosimetric measurements on the surface of the Moon. LND also provides observations of fast neutrons which are a result of the interaction of high-energy particle radiation with the lunar regolith and of their thermalized counterpart, thermal neutrons, which are a sensitive indicator of subsurface water content.

[2]  arXiv:2001.11030 [pdf, other]
Title: Equilibrium models of the Milky Way mass are biased high by the LMC
Comments: 7 pages, 6 figures. Submitted to MNRAS. Comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Recent measurements suggest that the Large Magellanic Cloud (LMC) may weigh as much as 25\% of the Milky Way. In this work we explore how such a large satellite affects mass estimates of the Milky Way based on equilibrium modelling of the stellar halo or other tracers. In particular, we show that if the LMC is ignored, the Milky Way mass is overestimated by as much as 50\%. This bias is due to the bulk motion in the outskirts of the Galaxy's halo and can be, at least in part, accounted for with a simple modification to the equilibrium modelling. Finally, we show that the LMC has a substantial effect on the orbit Leo I which acts to increase its present day speed relative to the Milky Way. We estimate that accounting for a $1.5\times10^{11} M_\odot$ LMC would lower the inferred Milky Way mass to $\sim10^{12} M_\odot$.

[3]  arXiv:2001.11032 [pdf, other]
Title: Universal transition diagram from dormant to actively accreting supermassive black holes
Comments: 9 pages (main text), 2 figures, 1 table, Submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

The vast majority of supermassive black holes (SMBHs) in the local universe exhibit levels of activity much lower than those expected from gas supplying rates onto the galactic nuclei, and only a small fraction of silent SMBHs can turn into active galactic nuclei. Revisiting observational data of very nearby SMBHs whose gravitational spheres of influence are spatially reached by the Chandra X-ray satellite, we find that the level of BH activity drastically increases from the quiescent phase when the inflow rate outside of the BH influence radius is higher than 0.1% of the Eddington accretion rate. We also show that the relation between the nuclear luminosity and gas accretion rate from the BH influence radius measured from X-ray observations is well described by the universal state transition of accreting SMBHs, as predicted by recent hydrodynamical simulations with radiative cooling and BH feedback. After the state transition, young massive stars should form naturally in the nucleus, as observed in the case of the nearest SMBH, Sagittarius A$^\ast$, which is currently quiescent but was recently active.

[4]  arXiv:2001.11033 [pdf, other]
Title: Homogeneity in the early chemical evolution of the Sextans dwarf Spheroidal galaxy
Comments: Submitted to A&A, 13 pages, 10 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

We present the high-resolution spectroscopic analysis of two new extremely metal-poor stars (EMPS) candidates in the dwarf spheroidal galaxy Sextans. These targets were pre-selected from medium resolution spectra centered around the Ca II triplet in the near-infrared and followed-up at higher resolution with VLT/UVES. We confirm their low metallicities with [Fe/H]=-2.95 and [Fe/H]=-3.01, placing them among the most metal-poor stars known in Sextans. The abundances of 18 elements, including C, Na, the alpha-elements, Fe-peak, and neutron capture elements, are determined. In particular, we present the first measurements of Zn in a classical dwarf at extremely low metallicity. There has been previous hints of a large scatter in the abundance ratios of the Sextans stellar population around [Fe/H] -3 when compared to other galaxies. We took the opportunity of this work to re-analyse the full sample of EMPS and find a Milky-Way -like plateau and a normal dispersion at fixed metallicity.

[5]  arXiv:2001.11036 [pdf, other]
Title: The Herschel view of the dense core population in the Ophiuchus molecular cloud
Comments: Accepted for publication in A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Herschel observations of nearby clouds in the Gould Belt support a paradigm for low-mass star formation, starting with the generation of molecular filaments, followed by filament fragmentation, and the concentration of mass into self-gravitating prestellar cores. With the unique far-infrared and submillimeter continuum imaging capabilities of the Herschel Space observatory, the closeby (d = 139 pc) Ophiuchus cloud was mapped at five wavelengths from 70 ${\mu}m$ to 500 ${\mu}m$ with the aim of providing a complete census of dense cores in this region, including unbound starless cores, bound prestellar cores, and protostellar cores. Taking advantage of the high dynamic range and multi-wavelength nature of the Herschel data, we used the multi-scale decomposition algorithms getsources and getfilaments to identify a complete sample of dense cores and filaments in the cloud and study their properties. The densest clouds of the Ophiuchus complex, L1688 and L1689, which thus far are only indirectly described as filamentary regions owing to the spatial distribution of their young stellar objects (YSOs), are confirmed to be dominated by filamentary structures. The tight correlation observed between prestellar cores and filamentary structures in L1688 and L1689 supports the view that solar-type star formation occurs primarily in dense filaments. While the sub clouds of the complex show disparities, L1689 being less efficient than L1688 at forming stars when considering their total mass budgets, both sub clouds share almost the same prestellar core formation efficiency in dense molecular gas. We also find evidence in the Herschel data for a remarkable concentric geometrical configuration in L1688 which is dominated by up to three arc-like compression fronts and presumably created by shockwave events emanating from the Sco OB2 association, including the neighboring massive (O9V) star ${\sigma}$ Sco.

[6]  arXiv:2001.11038 [pdf, other]
Title: A high-precision abundance analysis of the nuclear benchmark star HD 20
Comments: 23 pages (+10 pages appendix), 27 figures, 8 tables, revised version resubmitted to A&A
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We present our chemical abundance investigation of the metal-poor ([Fe/H]=-1.60 dex), r-process-enriched ([Eu/Fe]=0.73 dex) halo star HD 20 using novel and archival high-resolution spectra at outstanding signal-to-noise ratios. By combining one of the first asteroseismic gravity measurements in the metal-poor regime from a TESS light curve with non-LTE analyses of iron lines, we derive a set of highly accurate and precise stellar parameters. These allow us to delineate a chemical pattern comprised of solid detections of 48 elements, including 28 neutron-capture elements, which establishes HD 20 among the few benchmark stars that have almost complete patterns with low systematic dependencies on the stellar parameters. Our light-element (Z<30) abundances are representative of other, similarly metal-poor stars in the Galactic halo with contributions from core-collapse supernovae of type II. A comparison to the scaled solar r-pattern shows that the lighter neutron-capture elements (37<Z<60) are poorly matched. In particular, we find imprints of the weak r-process acting at low metallicities. Nonetheless, by comparing our detailed abundances to the observed metal-poor star BD +17 3248, we find a persistent residual pattern that is indicative of enrichment contributions from the s-process. We show that mixing with material from predicted yields of massive, rotating AGB stars at low metallicity considerably improves the fit. Based on a solar ratio of heavy- to light-s elements -- at odds with model predictions for the i-process -- and a missing clear residual pattern with respect to other stars with claimed contributions from this process, we refute (strong) contributions from such astrophysical sites providing intermediate neutron densities. Finally, nuclear cosmochronology is used to tie our detection of the radioactive element Th to an age estimate for HD 20 of $11.0\pm3.8$ Gyr. [abridged]

[7]  arXiv:2001.11040 [pdf, other]
Title: A multi-frequency ALMA characterization of substructures in the GM Aur protoplanetary disk
Comments: 31 pages, 15 figures, accepted by ApJ. Self-calibration and imaging scripts, images, and self-calibrated visibilities available at this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

The protoplanetary disk around the T Tauri star GM Aur was one of the first hypothesized to be in the midst of being cleared out by a forming planet. As a result, GM Aur has had an outsized influence on our understanding of disk structure and evolution. We present 1.1 and 2.1 mm ALMA continuum observations of the GM Aur disk at a resolution of ~50 mas (~8 au), as well as HCO$^+$ $J=3-2$ observations at a resolution of ~100 mas. The dust continuum shows at least three rings atop faint, extended emission. Unresolved emission is detected at the center of the disk cavity at both wavelengths, likely due to a combination of dust and free-free emission. Compared to the 1.1 mm image, the 2.1 mm image shows a more pronounced "shoulder" near R~40 au, highlighting the utility of longer-wavelength observations for characterizing disk substructures. The spectral index $\alpha$ features strong radial variations, with minima near the emission peaks and maxima near the gaps. While low spectral indices have often been ascribed to grain growth and dust trapping, the optical depth of GM Aur's inner two emission rings renders their dust properties ambiguous. The gaps and outer disk ($R>100$ au) are optically thin at both wavelengths. Meanwhile, the HCO$^+$ emission indicates that the gas cavity is more compact than the dust cavity traced by the millimeter continuum, similar to other disks traditionally classified as "transitional."

[8]  arXiv:2001.11042 [pdf, other]
Title: Pebble drift and planetesimal formation in protoplanetary discs with embedded planets
Comments: Accepted in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Nearly-axisymmetric gaps and rings are commonly observed in protoplanetary discs. The leading theory regarding the origin of these patterns is that they are due to dust trapping at the edges of gas gaps induced by the gravitational torques from embedded planets. If the concentration of solids at the gap edges becomes high enough, it could potentially result in planetesimal formation by the streaming instability. We test this hypothesis by performing global 1-D simulations of dust evolution and planetesimal formation in a protoplanetary disc that is perturbed by multiple planets. We explore different combinations of particle sizes, disc parameters, and planetary masses, and find that planetesimals form in all these cases. We also compare the spatial distribution of pebbles from our simulations with protoplanetary disc observations. Planets larger than one pebble isolation mass catch drifting pebbles efficiently at the edge of their gas gaps, and depending on the efficiency of planetesimal formation at the gap edges, the protoplanetary disc transforms within a few 100,000 years to either a transition disc with a large inner hole devoid of dust or to a disc with narrow bright rings. For simulations with planetary masses lower than the pebble isolation mass, the outcome is a disc with a series of weak ring patterns but no strong depletion between the rings. Lowering the pebble size artificially to 100 micrometer-sized "silt", we find that regions between planets get depleted of their pebble mass on a longer time-scale of up to 0.5 million years. These simulations also produce fewer planetesimals than in the nominal model with millimeter-sized particles and always have at least two rings of pebbles still visible after 1 Myr.

[9]  arXiv:2001.11043 [pdf, other]
Title: Systematic Variations of CO J=2-1/1-0 Ratio in The Barred Spiral Galaxy M83
Comments: Accepted for ApJ Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present spatial variations of the CO J=2-1/1-0 line ratio in M83 using Total Power array data from ALMA. While the intensities of these two lines correlate tightly, the ratio varies over the disk, with a disk average ratio of 0.69, and shows the galactic center and a two-arm spiral pattern. It is high (>0.7) in regions of high molecular gas surface density, but ranges from low to high ratios in regions of low surface density. The ratio correlates well with the spatial distributions and intensities of FUV and IR emissions, with FUV being the best correlated. It also correlates better with the ratio of IR intensities (70/350mic), a proxy for dust temperature, than with the IR intensities. Taken together, these results suggest either a direct or indirect link between the dust heating by the interstellar radiation field and the condition of GMCs, even though no efficient mechanism is known for a thermal coupling of dust and bulk gas in GMCs.

[10]  arXiv:2001.11044 [pdf, other]
Title: Testing low-redshift cosmic acceleration with large-scale structure
Comments: 7 pages, 5 figures. Comments welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We examine the cosmological implications of measurements of the void-galaxy cross-correlation at redshift $z=0.57$ combined with baryon acoustic oscillation (BAO) data at $0.1<z<2.4$. We find direct evidence of the late-time acceleration due to dark energy at $>10\sigma$ significance from these data alone, independent of the cosmic microwave background and supernovae. Using a nucleosynthesis prior on $\Omega_bh^2$, we measure the Hubble constant to be $H_0=72.3\pm1.9$ kms$^{-1}$Mpc$^{-1}$ from BAO+voids at $z<2$, and $H_0=69.0\pm1.2$ kms$^{-1}$Mpc$^{-1}$ when adding Lyman-$\alpha$ BAO at $z=2.34$, both independent of the CMB. Adding voids to CMB, BAO and supernova data greatly improves measurement of the dark energy equation of state, increasing the Figure of Merit by >40%, but remaining consistent with flat $\Lambda$CDM.

[11]  arXiv:2001.11045 [pdf, other]
Title: $M_{\rm{dust}}-M_{\star}$ Relation Hints at the Origin of Particle Traps in Protoplanetary Disks
Comments: Accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

[abridged] Demographic surveys of protoplanetary disks, mainly with ALMA, have provided access to a large range of disk dust masses ($M_{\rm{dust}}$) around stars with different stellar types and for different star-forming regions. These surveys found a linear relation in logarithmic scale between $M_{\rm{dust}}$ and $M_{\star}$ that steepens with time, but that is flatter for transition disks (TDs). We perform dust evolution models and include perturbations to the gas surface density with different amplitudes to investigate the effect of particle trapping on the $M_{\rm{dust}}-M_{\star}$ relation. These perturbations aim to mimic pressure bumps originated by planets. We focus on the effect caused by different stellar and disk masses because exoplanet statistics show a dependence of planet mass with stellar mass and metallicity. We find that models of dust evolution can reproduced the observed $M_{\rm{dust}}-M_{\star}$ relation in different star-forming regions when strong pressure bumps are included and when the disk mass scales with stellar mass (case of $M_{\rm{disk}}=0.05\,M_\star$ in our models). This result arises from dust trapping and dust growth beyond centimeter-size grains inside pressure bumps. However, the flatter relation of $M_{\rm{dust}}-M_{\star}$ for TDs and disks with substructures cannot be reproduced by the models, unless the formation of boulders is inhibited inside pressure bumps. In the context of planets originating pressure bumps, our results agree with the current exoplanet statistics about giant planet occurrence increasing with stellar mass, but we cannot conclude about the type of planets needed in the case of low mass stars. This is because for $M_\star<1\,M_\odot$, the observed $M_{\rm{dust}}$ obtained from models is very low due to the efficient growth of dust particles beyond centimeter sizes (boulders) inside pressure bumps.

[12]  arXiv:2001.11046 [pdf, other]
Title: The MASSIVE Survey XIV -- Stellar Velocity Profiles and Kinematic Misalignments from 200 pc to 20 kpc in Massive Early-type Galaxies
Comments: Accepted for publication in The Astrophysical Journal. 15 pages, 7 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We use high spatial resolution stellar velocity maps from the Gemini GMOS integral-field spectrograph (IFS) and wide-field velocity maps from the McDonald Mitchell IFS to study the stellar velocity profiles and kinematic misalignments from $\sim 200$ pc to $\sim 20$ kpc in 20 early-type galaxies with stellar mass $M_* > 10^{11.7} M_\odot$ in the MASSIVE survey. While 80% of the galaxies have low spins ($\lambda < 0.1$) and low rotational velocities ($< 50$ km/s) in both the central region and the main body, we find a diverse range of velocity features and misalignment angles. For the 18 galaxies with measurable central kinematic axes, 10 have well aligned kinematic axis and photometric major axis, and the other 8 galaxies have misalignment angles that are distributed quite evenly from $15^\circ$ to the maximal value of $90^\circ$. There is a strong correlation between central kinematic misalignment and galaxy spin, where all 4 galaxies with significant spins have well aligned kinematic and photometric axes, but only 43% of the low-spin galaxies are well aligned. The central and main-body kinematic axes within a galaxy are not always aligned. When the two kinematic axes are aligned ($\sim 60$% of the cases), they are either also aligned with the photometric major axis or orthogonal to it. We find 13 galaxies to also exhibit noticeable local kinematic twists, and one galaxy to have a counter-rotating core. A diverse assembly history consisting of multiple gas-poor mergers of a variety of progenitor mass ratios and orbits is likely to be needed to account for the predominance of low spins and the wide range of central and main-body velocity features reported here for local massive ETGs.

[13]  arXiv:2001.11048 [pdf, other]
Title: MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b
Comments: 22 pages, 21 figures, accepted for publication in MNRAS on 23 January 2020
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)

In this third paper of the MOVES (Multiwavelength Observations of an eVaporating Exoplanet and its Star) programme, we combine Hubble Space Telescope far-ultraviolet observations with XMM-Newton/Swift X-ray observations to measure the emission of HD 189733 in various FUV lines, and its soft X-ray spectrum. Based on these measurements we characterise the interstellar medium toward HD 189733 and derive semi-synthetic XUV spectra of the star, which are used to study the evolution of its high-energy emission at five different epochs. Two flares from HD 189733 are observed, but we propose that the long-term variations in its spectral energy distribution have the most important consequences for the environment of HD 189733b. Reduced coronal and wind activity could favour the formation of a dense population of Si$^{2+}$ atoms in a bow-shock ahead of the planet, responsible for pre- and in-transit absorption measured in the first two epochs. In-transit absorption signatures are detected in the Lyman-$\alpha$ line in the second, third and fifth epochs, which could arise from the extended planetary thermosphere and a tail of stellar wind protons neutralised via charge-exchange with the planetary exosphere. We propose that increases in the X-ray irradiation of the planet, and decreases in its EUV irradiation causing lower photoionisation rates of neutral hydrogen, favour the detection of these signatures by sustaining larger densities of H$^{0}$ atoms in the upper atmosphere and boosting charge-exchanges with the stellar wind. Deeper and broader absorption signatures in the last epoch suggest that the planet entered a different evaporation regime, providing clues as to the link between stellar activity and the structure of the planetary environment.

[14]  arXiv:2001.11063 [pdf, other]
Title: The VANDELS survey: A strong correlation between Ly$α$ equivalent width and stellar metallicity at $\mathbf{3\leq z \leq 5}$
Comments: 10 pages, 6 figures, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present the results of a new study investigating the relationship between Ly$\alpha$ equivalent width ($W_{\lambda}$(Ly$\alpha$)) and the metallicity of the ionizing stellar population ($Z_{\star}$) for a sample of $768$ star-forming galaxies at $3 \leq z \leq 5$ drawn from the VANDELS survey. Dividing our sample into quartiles of rest-frame $W_{\lambda}$(Ly$\alpha$) across the range $-58 \unicode{xC5} \lesssim$ $W_{\lambda}$(Ly$\alpha$) $\lesssim 110 \unicode{xC5}$ we determine $Z_{\star}$ from full spectral fitting of composite far-ultraviolet (FUV) spectra and find a clear anti-correlation between $W_{\lambda}$(Ly$\alpha$) and $Z_{\star}$. Our results indicate that $Z_{\star}$ decreases by a factor $\gtrsim 3$ between the lowest $W_{\lambda}$(Ly$\alpha$) quartile ($\langle$$W_{\lambda}$(Ly$\alpha$)$\rangle=-18\unicode{xC5}$) and the highest $W_{\lambda}$(Ly$\alpha$) quartile ($\langle$$W_{\lambda}$(Ly$\alpha$)$\rangle=24\unicode{xC5}$). Similarly, galaxies typically defined as Lyman Alpha Emitters (LAEs; $W_{\lambda}$(Ly$\alpha$) $>20\unicode{xC5}$) are, on average, metal poor with respect to the non-LAE galaxy population ($W_{\lambda}$(Ly$\alpha$) $\leq20\unicode{xC5}$) with $Z_{\star}$$_{\rm{non-LAE}}\gtrsim 2 \times$ $Z_{\star}$$_{\rm{LAE}}$. Finally, based on the best-fitting stellar models, we estimate that the increasing strength of the stellar ionizing spectrum towards lower $Z_{\star}$ is responsible for $\simeq 15-25\%$ of the observed variation in $W_{\lambda}$(Ly$\alpha$) across our sample, with the remaining contribution ($\simeq 75-85\%$) being due to a decrease in the HI/dust covering fractions in low $Z_{\star}$ galaxies.

[15]  arXiv:2001.11065 [pdf, other]
Title: An extended theoretical scenario for Classical Cepheids. I. Modeling Galactic Cepheids in the Gaia photometric system
Comments: Accepted for publication on ApJ Supplement, 43 pages, 10 figures, 12 tables
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

We present a new extended and detailed set of models for Classical Cepheid pulsators at solar chemical composition ($Z=0.02$, $Y=0.28$) based on a well tested nonlinear hydrodynamical approach. In order to model the possible dependence on crucial assumptions such as the Mass-Luminosity relation of central Helium burning intermediate-mass stars or the efficiency of superadiabatic convection, the model set was computed by varying not only the pulsation mode and the stellar mass but also the Mass-Luminosity relation and the mixing length parameter that is used to close the system of nonlinear hydrodynamical and convective equations. The dependence of the predicted boundaries of the instability strip as well as of both light and radial velocity curves on the assumed Mass-Luminosity and the efficiency of superadiabatic convection is discussed. Nonlinear Period-Mass-Luminosity-Temperature, Period-Radius and Period-Mass-Radius relations are also computed. The theoretical atlas of bolometric light curves for both the fundamental and first overtone mode has been converted in the Gaia filters $G$, $G_{BP}$ and $G_{BR}$ and the corresponding mean magnitudes have been derived. Finally the first theoretical Period-Luminosity-Color and Period-Wesenheit relations in the Gaia filters are provided and the resulting theoretical parallaxes are compared with Gaia Data Release 2 results for both fundamental and first overtone Galactic Cepheids.

[16]  arXiv:2001.11067 [pdf, other]
Title: The Vera Rubin Observatory Legacy Survey of Space and Time and the Low Surface Brightness Universe
Comments: Invited talk, to appear in the Proceedings of the IAU Symposium 355, 'The Realm of the Low-surface-brightness Universe'
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The 8.4m Vera Rubin Observatory Legacy Survey of Space and Time (LSST) will start a ten-year survey of the southern hemisphere sky in 2023. LSST will revolutionise low surface brightness astronomy. It will transform our understanding of galaxy evolution, through the study of low surface brightness features around galaxies (faint shells, tidal tails, halos and stellar streams), discovery of low surface brightness galaxies and the first set of statistical measurements of the intracluster light over a significant range of cluster masses and redshifts.

[17]  arXiv:2001.11068 [pdf, other]
Title: Role of the crust on the tidal deformability of a neutron star within a unified treatment of dense matter
Comments: 23 pages, 12 figures
Journal-ref: Phys. Rev. C 101, 015806 (2020)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)

The role of the crust on the tidal deformability of a cold nonaccreted neutron star is studied using the recent unified equation of state BSk24. This equation of state, which is based on the nuclear-energy density functional theory, provides a thermodynamically consistent description of all stellar regions. Results obtained with this equation of state are compared to those calculated for a putative neutron star made entirely of homogeneous matter. The presence of the crustal layers is thus found to significantly reduce the Love number $k_2$, especially for low-mass stars. However, this reduction mainly arises from the increase in the stellar radius almost independently of the equation of state. This allows for a simple analytic estimate of $k_2$ for realistic neutron stars using the equation of state of homogeneous matter only.

[18]  arXiv:2001.11069 [pdf]
Title: Hoki: Making BPASS accessible through Python
Comments: 3 pages, Published in JOSS, GitHub: this https URL
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

We now know that a large number of stars are born in multiple systems. Additionally, more than 70% of massive stars are found in close binary systems, meaning that they will interact over the course of their lifetime. This has strong implications for their evolution as well as the transients (e.g supernovae) and the potential gravitational wave progenitors they produce. Therefore, in order to understand and correctly interpret astronomical observations of stellar populations, we must use theoretical models able to account for the effects of binary stars. This is the case of the Binary Population and Spectral Synthesis code (BPASS), which has been a staple of the field for over 10 years. As is the case for most other theoretical models, the data products of BPASS are large, varied and complex. As a result, their use requires a level of expertise that is not immediately accessible to a wider community that may hold key observational data. The goal of hoki is to bridge the gap between observation and theory, by providing a set of tools to make BPASS data easily accessible and facilitate analysis. The use of Python is deliberate as it is a ubiquitous language within Astronomy. This allows BPASS results to be used naturally within the pre-existing workflow of most astronomers.

[19]  arXiv:2001.11076 [pdf]
Title: The ALMA Development Program: Roadmap to 2030
Authors: John Carpenter (Joint ALMA Observatory), Daisuke Iono (National Astronomical Observatory of Japan), Francisca Kemper (European Southern Observatory), Al Wootten (National Radio Astronomy Observatory)
Journal-ref: Monthly Newsletter of International URSI Commission J Radio Astronomy January 2020
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The Atacama Large Millimeter/submillimeter Array (ALMA) is the premier telescope for sensitive, high-resolution observations at millimeter and submillimeter wavelengths. The array consists of fifty 12-m diameter antennas that can be reconfigured to baselines as long as 16 km, twelve 7-m antennas that sample the short visibility spacings, and four 12-m antennas that provide total power capabilities for spectral line and continuum observations. Located in the Atacama desert in northern Chile at an elevation of 5000 m on the Chajnantour plateau, the ALMA site provides excellent observing conditions with low precipitable water vapor. The large number of antennas, the high-altitude site, and excellent receivers with low-noise performance provide an extremely sensitive, flexible instrument for submillimeter imaging.

[20]  arXiv:2001.11083 [pdf, other]
Title: Physics of Prodigious Lyman Continuum Leakers
Authors: Renyue Cen (Princeton)
Comments: 15 pages, 4 figures, in press of ApJL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

An analysis of the dynamics of a star formation event is performed. It is shown that galaxies able to drive leftover gas to sufficient altitudes in a few million years are characterized by two basic properties: small sizes (<1kpc) and high star formation rate surface densities (Sigma_SFR > 10 Msun/yr/kpc2). For the parameter space of relevance, the outflow is primarily driven by supernovae with radiation pressure being significant but subdominant. Our analysis provides the unifying physical origin for a diverse set of observed LyC leakers, including the green-peas galaxies, [SII]-weak galaxies, Lyman-alpha emitters, with these two characteristics as the common denominator. Among verifiable physical properties of LyC leakers, we predict that (1) the newly formed stellar masses are are typically in the range of 1e8-1e10 Msun, except perhaps ULIRGs, (2) the outflow velocities are typically in the range typically of 100-600km/s, but may exceed 1e3 km/s in ULIRGs, with a strong positive correlation between the stellar masses formed and the outflow velocities, (3) the overall escape fraction of galaxies is expected to increase with increasing redshift, given the cosmological trend that galaxies become denser and more compact with increasing redshift. In addition, two interesting by-product predictions are also borne out. First, ULIRGs appear to be in a parameter region where they should be prodigious LyC leakers, unless there is a large ram-pressure. Second, Lyman break galaxies (LBGs) are not supposed to be prodigious LyC leakers in our model, given their claimed effective radii exceeding 1kpc.

[21]  arXiv:2001.11105 [pdf, other]
Title: Exploring the dispersion measure of the Milky Way halo
Comments: 5 pages, 4 figures. Submitted to MNRAS Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Fast radio bursts offer the opportunity to place new constraints on the mass and density profile of hot and ionized gas in galactic haloes. We test here the X-ray emission and dispersion measure predicted by different gas profiles for the halo of the Milky Way. We examine a range of models, including entropy stability conditions and external pressure continuity. We find that incorporating constraints from X-ray observations leads to favouring dispersion measures on the lower end of the range given by these models. We show that the dispersion measure of the Milky Way halo could be less than 10 cm$^{-3}$ pc in the most extreme model we consider, which is based on constraints from O VII absorption lines. However, the models allowed by the soft X-ray constraints span more than an order of magnitude in dispersion measures. Additional information on the distribution of gas in the Milky Way halo could be obtained from the signature of a dipole in the dispersion measure of fast radio bursts across the sky, but this will be a small effect for most cases.

[22]  arXiv:2001.11112 [pdf, other]
Title: TraMoS V. Updated ephemeris and multi-epoch monitoring of the hot Jupiters WASP-18Ab, WASP-19b, and WASP-77Ab
Comments: 20 pages, 8 figures. Accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

We present 22 new transit observations of the exoplanets WASP-18Ab, WASP-19b, and WASP-77Ab, from the Transit Monitoring in the South (TraMoS) project. We simultaneously model our newly collected transit light curves with archival photometry and radial velocity data, to obtain refined physical and orbital parameters. We include TESS light curves of the three exoplanets to perform an extended analysis of the variations in their transit mid-time (TTV) and to refine their planetary orbital ephemeris. We did not find significant $\rm TTV_{RMS}$ variations larger than 47, 65, and 86 seconds for WASP-18Ab, WASP-19b, and WASP-77Ab, respectively. Dynamical simulations were carried out to constrain the masses of a possible perturber. The observed RMS could be produced by a perturber body with an upper limit mass of 9, 2.5, 11 and $4~M_{\oplus}$ in 1:2, 1:3, 2:1, and 3:1 resonances in the WASP-18Ab system. In the case of WASP-19b, companions with masses up to 0.26, 0.65, 1 and $2.8~M_{\oplus}$, in 1:2, 2:1, 3:1, and 5:3 resonances, produce the RMS. And for the WASP-77Ab system, a planet with mass between $1.5-9~M_{\oplus}$ in 1:2, 1:3, 2:1, 2:3, 3:1, 3:5, 5:3 resonances. Comparing our results with RV variations, we discard massive companions with $350~M_{\oplus}$ in 17:5 resonance for WASP-18Ab, $95~M_{\oplus}$ in 4:1 resonance for WASP-19b and $105~M_{\oplus}$ in 5:2 resonance for WASP-77Ab. Finally, using a Lomb-Scargle period search we find no evidence of a periodic trend on our TTV data for the three exoplanets.

[23]  arXiv:2001.11117 [pdf, ps, other]
Title: Summary of the 14th IACHEC Meeting
Comments: 15 pies
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

We summarize the 14th meeting of the International Astronomical Consortium for High Energy Calibration (IACHEC) held at \textit{Shonan Village} (Kanagawa, Japan) in May 2019. Sixty scientists directly involved in the calibration of operational and future high-energy missions gathered during 3.5 days to discuss the status of the cross-calibration between the current international complement of X-ray observatories, and the possibilities to improve it. This summary consists of reports from the various WGs with topics ranging from the identification and characterization of standard calibration sources, multi-observatory cross-calibration campaigns, appropriate and new statistical techniques, calibration of instruments and characterization of background, communication and preservation of knowledge, and results for the benefit of the astronomical community.

[24]  arXiv:2001.11118 [pdf, ps, other]
Title: Self-consistent Semi-analytic Modeling of Feedback During Primordial Star Formation and Reionization
Comments: 16 pages, 7 figures, to be submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present a new semi-analytic model of the formation of the first stars. Our method takes dark matter halo merger trees (including 3-dimensional spatial information) from cosmological N-body simulations as input and applies analytic prescriptions to compute both the Population III (Pop III) and metal-enriched star formation histories. We have developed a novel method to accurately compute the major feedback processes affecting Pop III star formation: H$_2$ photodissociation from Lyman-Werner (LW) radiation, suppression of star formation due to inhomogeneous reionization, and metal enrichment via supernovae winds. Our method utilizes a grid-based approach relying on fast Fourier transforms (FFTs) to rapidly track the LW intensity, ionization fraction, and metallicity in 3-dimensions throughout the simulation box. We present simulations for a wide range of astrophysical model parameters from $z\approx 30-6$. Initially long-range LW feedback and local metal enrichment and reionization feedback dominate. However, for $z \lesssim 15$ we find that the star formation rate density (SFRD) of Pop III stars is impacted by the combination of external metal enrichment (metals from one halo polluting other pristine halos) and inhomogeneous reionization. We find that the interplay of these processes is particularly important for the Pop III SFRD at $z \lesssim 10$. Reionization feedback delays star formation long enough for metal bubbles to reach halos that would otherwise form Pop III stars. Including these effects can lead to more than an order of magnitude decrease in the Pop III SFRD at $z=6$ compared to LW feedback alone.

[25]  arXiv:2001.11138 [pdf, other]
Title: Narrowband Ca Photometry for Dwarf Spheroidal Galaxies. I. Chemostructural Study on Draco, Sextans, and Canes Venatici I
Comments: Accepted for publication in ApJS, data will be available at this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

A few dozen dwarf satellite galaxies of the Milky Way have been discovered, which are often viewed as the remaining building blocks of our Galaxy. The follow-up spectroscopy showed that dwarf galaxies have a sizeable spread in their metallicities. Several scenarios were suggested to explain the metallicity spread, which can be tested by the structural patterns of stellar subpopulations with distinct metallicities. However, such chemical plus structural examination, to which we refer to as "chemostructural study" is hindered by the lack of stars with spectroscopic metallicity. Here we propose the Ca$-$$by$ photometry as an alternative way to secure metallicities for a 2$-$3 orders of magnitude larger stellar sample than the spectroscopic sample and thus enable us to perform a chemostructural study on dwarf galaxies. In particular, we use the $hk$ index [$\equiv($Ca$-b)-(b-y)$], whose validity as a photometric metallicity indicator (and crass insensitivity to age) for red-giant-branch stars was upheld via Galactic globular clusters, and observe three dwarf spheroidal galaxies$-$Draco, Sextans, and Canes Venatici I (CVnI)$-$with Subaru/Suprime-Cam. We find that in all the galaxies the metal-rich stellar populations are more centrally concentrated than the metal-poor counterparts, suggesting that the central regions of the galaxies underwent extended star formation. Such a negative radial metallicity gradient for Sextans and CVnI opposes to the traditional spectroscopic results. We also find that their metallicity distribution functions (MDFs) can be characterized by a unimodal, skewed Gaussian shape with a metal-rich peak and a metal-poor tail. We discuss their features in the chemostructure and MDF in terms of dwarf galaxy formation theories.

[26]  arXiv:2001.11146 [pdf, other]
Title: ART$^2$: A 3D Parallel Multi-wavelength Radiative Transfer Code for Continuum and Atomic and Molecular Lines
Authors: Yuexing Li (Penn State), Ming F. Gu (UC Berkeley), Hidenobu Yajima (University of Tsukuba), Qirong Zhu (Carnegie Mellon), Moupiya Maji (University of Geneva)
Comments: Submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP)

ART$^2$ is a 3D multi-wavelength Monte Carlo radiative transfer (RT) code that couples continuum and emission lines to track the propagation of photons and their interactions with the interstellar medium (ISM). The previous version of ART$^2$, which included continuum and Ly$\alpha$ line, has been extensively applied to hydrodynamics simulations to study multi-band properties of galaxies and ISM. Here, we describe new implementations of non-local thermodynamic equilibrium RT of molecular and atomic fine structure emission lines, and the parallelization of the code using a number of novel methods. The new ART$^2$ can efficiently and self-consistently produce a full spectrum that includes both continuum and lines such as [CII], [NII], [OIII], Ly$\alpha$, and CO. These essential features, together with the multi-phase ISM model and the adaptive grid, make ART$^2$ a multi-purpose code to study multi-wavelength properties of a wide range of astrophysical systems from planetary disks to large-scale structures.
To demonstrate the capability of the new ART$^2$, we applied it to two hydrodynamics simulations: the zoom-in Milky Way Simulation to obtain panchromatic properties of individual galaxies, and the large-scale IllustrisTNG100 Simulation to obtain global properties such as the line intensity mappings. These products are essential for a broad array of studies such as the correlations between physical and panchromatic properties and their evolution. By enabling direct comparison between numerical simulations and multi-band observations, ART$^2$ provides a crucial theoretical framework for the interpretations of existing observations, the plan for future surveys, and the synergy between multi-band galaxy surveys and line intensity mappings. Therefore, ART$^2$ can provide a powerful and versatile tool to bridge the gap between theories and observations of cosmic structures.

[27]  arXiv:2001.11148 [pdf, ps, other]
Title: Neutrino transport with Monte Carlo method: I. Towards fully consistent implementation of nucleon recoils in core-collapse supernova simulations
Comments: 22 pages, 11 figures, submitted to ApJS
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

The small energy exchange via nucleon recoils in neutrino-nucleon scattering is now supposed to be one of the important factors for successful explosion of core-collapse supernovae (CCSNe) as they can change neutrino spectra through accumulation of a large number of scatterings. In finite-difference methods employed for neutrino transport in CCSN simulations, we normally can not afford to deploy a large enough number of energy bins needed to resolve this small energy exchange and sub-grid techniques are employed one way or another. In this paper we study quantitatively with the Monte Carlo (MC) method how well such a treatment performs. We first investigate the effects of nucleon recoils on the neutrino spectra and confirm that the average energy is reduced by $\sim$15% for heavy-lepton neutrinos and by much smaller quantities for other types of neutrinos in a typical post-bounce situation. It is also observed that the nucleon scattering dominates the electron scattering in the thermalization of neutrino spectra in all flavors. We then study possible artifacts that the coarse energy grid may produce in the finite-difference methods. In order to mimic the latter calculation, we re-distribute MC particles in each energy bin after a certain interval in a couple of ways and study how the results are affected and depend on the energy-resolution. We also discuss possible implications of our results for the finite-difference methods.

[28]  arXiv:2001.11149 [pdf, other]
Title: Updated constraints on superconducting cosmic strings from the astronomy of fast radio bursts
Comments: 7 pages, 3 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

In this article, we study the updated constraints upon the radio transient signals arisen from superconducting cosmic strings (SCSs) in light of the recent observational developments of fast radio bursts (FRBs) astronomy. By assuming that the currents in these strings follow the Poisson distribution, we show that two parameters can be severely limited by FRB experiments, which are the characteristic tension and current of cosmic strings, respectively. In particular, we investigate data sets from two FRB experiments namely: Parkes and ASKAP. Our analyses show that, Parkes jointly with ASKAP can constrain the parameter space for superconducting cosmic strings well enough. Our numerical calculation estimates that the possibly allowed parameter space for strings are give by $G\mu \sim [10^{-16}, 10^{-13}]$ and $I_c\sim [10^{0}, 10^{2}]$GeV.

[29]  arXiv:2001.11161 [pdf, other]
Title: On the Chemical and Kinematic Consistency Between N-rich Metal-poor Field Stars and Enriched Populations in Globular Clusters
Comments: Accepted by ApJ. Tables 2 and 3 are now available upon request, and will be uploaded online
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Interesting chemically peculiar field stars may reflect their stellar evolution history and their possible origin in a different environment from where they are found now, which is one of the most important research fields in Galactic archaeology. To explore this further, we have used the CN-CH bands around 4000 A to identify N-rich metal-poor field stars in LAMOST DR3. Here we expand our N-rich metal-poor field star sample to ~100 stars in LAMOST DR5, where 53 of them are newly found in this work. We investigate light elements of the common stars between our sample and APOGEE DR14. While Mg, Al, and Si abundances generally agree with the hypothesis that N-rich metal-poor field stars come from enriched populations in globular clusters, it is still inconclusive for C, N, and O. After integrating the orbits of our N-rich field stars and a control sample of normal metal-poor field stars, we find that N-rich field stars have different orbital parameter distributions compared to the control sample, specifically, apocentric distances, maximum vertical amplitude (Zmax), orbital energy, and z direction angular momentum (Lz). The orbital parameters of N-rich field stars indicate that most of them are inner-halo stars. The kinematics of N-rich field stars support their possible GC origin. The spatial and velocity distributions of our bona fide N-rich field star sample are important observational evidence to constrain simulations of the origin of these interesting objects.

[30]  arXiv:2001.11173 [pdf, other]
Title: A Cryogenic Silicon Interferometer for Gravitational-wave Detection
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Detectors (physics.ins-det)

The detection of gravitational waves from compact binary mergers by LIGO has opened the era of gravitational wave astronomy, revealing a previously hidden side of the cosmos. To maximize the reach of the existing LIGO observatory facilities, we have designed a new instrument that will have 5 times the range of Advanced LIGO, or greater than 100 times the event rate. Observations with this new instrument will make possible dramatic steps toward understanding the physics of the nearby universe, as well as observing the universe out to cosmological distances by the detection of binary black hole coalescences. This article presents the instrument design and a quantitative analysis of the anticipated noise floor.

[31]  arXiv:2001.11199 [pdf, ps, other]
Title: Gaia's Detectability of Black Hole-Main Sequence Star Binaries Formed in Open Clusters
Comments: 10 pages, 9 figures, submitted to PASJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

Black hole-main sequence star (BH-MS) binaries are one of the targets of the future data releases of the astrometric satellite $Gaia$. They are supposed to be formed in two main sites: a galactic field and star clusters. However, previous work has never predicted the number of BH-MS binaries originating in the latter site. In this paper, we estimate the number of BH-MS binaries formed in open clusters and detectable with $Gaia$ based on the results of $N$-body simulations. By considering interstellar extinction in the Milky Way (MW) and observational constraints, we predict $\sim 10$ BH-MS binaries are observable. In particular, binaries with relatively less massive MSs ($\lesssim 5M_{\odot}$), longer orbital periods ($\gtrsim 1.5\;$year) and higher eccentricities ($e \gtrsim 0.1$) are more likely to be formed in open clusters rather than in the MW galactic field. We also find that chemical abundance patterns of companion MSs will help us to identify the origin of the binaries as star clusters. Such MSs are not polluted by outflows of the BH progenitors, such as stellar winds and supernova ejecta.

[32]  arXiv:2001.11219 [pdf, other]
Title: PBH evaporation, baryon asymmetry,and dark matter
Comments: 25 pages, 25 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Sufficiently light primordial black holes (PBH) could evaporate in the very early universe and dilute the preexisting baryon asymmetry and/or the frozen density of stable relics. The effect is especially strong in the case that PBHs decayed if and when they dominated the cosmological energy density. The size of the reduction is first calculated analytically under the simplifying assumption of the delta-function mass spectrum of PBH and in instant decay approximation. In the realistic case of exponential decay and for an extended mass spectrum of PBH the calculations are made numerically. Resulting reduction of the frozen number density of the supersymmetric relics reopens for them a window to become viable dark matter particles.

[33]  arXiv:2001.11221 [pdf, other]
Title: Revisitation of time delay interferometry combinations that suppress laser noise in LISA
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)

With the purpose of understanding how time delay interferometry (TDI) combinations can best be used for the characterisation of LISA instrumental noise, we revisit their laser frequency noise cancellation properties. We have developed an algorithm to search for all possible combinations that suppress noise at the same level as the X, Y and Z classical combination. The algorithm calculates delays using symbolic formulas that explicitly include velocities and accelerations of satellites up to the relevant order. In addition, once a combination has been identified, delays are verified by solving numerically the relevant equations using Keplerian orbits and Shapiro delay corrections. We find that the number of combinations that suppress the noise is larger than what was reported in the literature. In particular we find that some combinations that were thought to only partly suppress the noise, in reality do suppress it at the same level of accuracy as the basic X, Y and Z combinations.

[34]  arXiv:2001.11227 [pdf, other]
Title: Optical Linear Polarization toward the Open Star Cluster Casado Alessi 1
Comments: 13 Pages, 9 Figures, 3 Tables. Accepted for publication in AJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We present B-, V-, R-, and I-bands linear polarimetric observations of 73 stars in the direction of open star cluster Casado Alessi 1 (hereafter Alessi 1). We aim to use polarimetry as a tool to investigate the properties and distribution of dust grains toward the direction of the cluster. The polarimetric observations were carried out using the ARIES IMaging POLarimeter mounted at the 104 cm telescope of ARIES, Nainital (India). Using the Gaia photometric data the age and distance of the cluster are estimated to be $0.8\pm0.1$ Gyr and $673\pm98$ pc, respectively. A total of 66 stars with a 26 arcmin radius from the cluster are identified as members of the cluster using the astrometric approach. Out of these 66 members, 15 stars were observed polarimetrically and found to have the same value of polarization. The majority of the stars in the region follow the general law of the polarization for the interstellar medium, indicating that polarization toward the cluster Alessi 1 is dominated by foreground dust grains. The average values of the maximum polarization ($P_{max}$) and the wavelength corresponding to the maximum polarization ($\lambda_{max}$) toward the cluster are found to be $0.83\pm0.03$% and $0.59\pm0.04$ $\mu$m, respectively. Also, dust grains toward the cluster appear to be aligned, possibly due to the galactic magnetic field.

[35]  arXiv:2001.11228 [pdf, other]
Title: Astronuclear Physics: a Tale of the Atomic Nuclei in the Skies
Comments: 100 pages, 24 figures, accepted for publication in the "Progress in Particle and Nuclear Physics" Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)

A century ago, nuclear physics entered astrophysics, giving birth to a new field of science referred to as "Nuclear Astrophysics". With time, it developed at an impressive pace into a vastly inter- and multidisciplinary discipline bringing into its wake not only astronomy and cosmology, but also many other sub-fields of physics, especially particle, solid-state and computational physics, as well as chemistry, geology and even biology. The present Astronuclear Physics review focusses primarily on the facets of nuclear physics that are of relevance to astronomy and astrophysics, the theoretical aspects being of special concern here.

[36]  arXiv:2001.11239 [pdf, ps, other]
Title: Deeply cooled core of the Phoenix galaxy cluster imaged by ALMA with the Sunyaev-Zel'dovich effect
Comments: 18 pages, 16 figures. Accepted for publication in PASJ
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

We present measurements of the thermal Sunyaev-Zel'dovich effect (SZE) toward SPT-CL J2334-4243 (the Phoenix galaxy cluster) at z=0.597 by the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 3. The SZE is imaged at 5" resolution (corresponding to the physical scale of 23kpc/h) within 200kpc/h from the central galaxy with the peak signal-to-noise ratio exceeding 11. Combined with the Chandra X-ray image, the ALMA SZE data further allow for non-parametric deprojection of electron temperature, density, and entropy. Our method can minimize contamination by the central AGN and the X-ray absorbing gas within the cluster, both of which largely affect the X-ray spectrum. We find no significant asymmetry or disturbance in the SZE image within the current measurement errors. The detected SZE signal agrees well with the average pressure profile of local cool-core clusters. Unlike any other known clusters, however, gas temperature drops by at least a factor of 5 toward the center. We identify ~6x10^{11} M_sun cool gas with temperature ~3keV in the inner 20kpc/h. Taken together, our results imply that the gas is indeed cooling efficiently and nearly isobarically down to this radius in the Phoenix cluster.

[37]  arXiv:2001.11252 [pdf, other]
Title: RASCAS: RAdiation SCattering in Astrophysical Simulations
Comments: Accepted for publication in A&A. Code available at this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Resonant lines are powerful probes of the interstellar and circumgalactic medium of galaxies. Their transfer in gas being a complex process, the interpretation of their observational signatures, either in absorption or in emission, is often not straightforward. Numerical radiative transfer simulations are needed to accurately describe the travel of resonant line photons in real and in frequency space, and to produce realistic mock observations. This paper introduces RASCAS, a new public 3D radiative transfer code developed to perform the propagation of any resonant line in numerical simulations of astrophysical objects. RASCAS was designed to be easily customisable and to process simulations of arbitrarily large sizes on large supercomputers. RASCAS performs radiative transfer on an adaptive mesh with an octree structure using the Monte Carlo technique. RASCAS features full MPI parallelisation, domain decomposition, adaptive load-balancing, and a standard peeling algorithm to construct mock observations. The radiative transport of resonant line photons through different mixes of species (e.g. \ion{H}{i}, \ion{Si}{ii}, \ion{Mg}{ii}, \ion{Fe}{ii}), including their interaction with dust, is implemented in a modular fashion to allow new transitions to be easily added to the code. RASCAS is very accurate and efficient. It shows perfect scaling up to a minimum of a thousand cores. It has been fully tested against radiative transfer problems with analytic solutions and against various test cases proposed in the literature. Although it was designed to describe accurately the many scatterings of line photons, RASCAS may also be used to propagate photons at any wavelength (e.g. stellar continuum or fluorescent lines), or to cast millions of rays to integrate the optical depths of ionising photons, making it highly versatile.

[38]  arXiv:2001.11254 [pdf, other]
Title: Is the High-Resolution Coronal Imager Resolving Coronal Strands? Results from AR 12712
Comments: 19 pages, 10 images, 3 tables
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Following the success of the first mission, the High-Resolution Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1) on 29th May 2018 from the White Sands Missile Range, NM, USA. On this occasion, 329 seconds of 17.2 nm data of target active region AR 12712 was captured with a cadence of ~4s, and a plate scale of 0.129''/pixel. Using data captured by Hi-C 2.1 and co-aligned observations from SDO/AIA 17.1 nm we investigate the widths of 49 coronal strands. We search for evidence of substructure within the strands that is not detected by AIA, and further consider whether these strands are fully resolved by Hi-C 2.1. With the aid of Multi-Scale Gaussian Normalization (MGN), strands from a region of low-emission that can only be visualized against the contrast of the darker, underlying moss are studied. A comparison is made between these low-emission strands with those from regions of higher emission within the target active region. It is found that Hi-C 2.1 can resolve individual strands as small as ~202km, though more typical strands widths seen are ~513km. For coronal strands within the region of low-emission, the most likely width is significantly narrower than the high-emission strands at ~388km. This places the low-emission coronal strands beneath the resolving capabilities of SDO/AIA, highlighting the need of a permanent solar observatory with the resolving power of Hi-C.

[39]  arXiv:2001.11277 [pdf, other]
Title: Formation channels of slowly rotating early-type galaxies
Comments: 25 pages, 13 figures, Figure 12 illustrates the main difference between core or core-less and slow or fast rotators; data can be obtained from the Atlas3D survey web site, see this http URL
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We study the evidence for a diversity of formation processes in early-type galaxies by presenting the first complete volume-limited sample of slow rotators with both integral-field kinematics from the ATLAS3D Project and high spatial resolution photometry from the Hubble Space Telescope. Analysing the nuclear surface brightness profiles of 12 newly imaged slow rotators, we classify their light profiles as core-less, and place an upper limit to the core size of ~10 pc. Considering the full magnitude and volume-limited ATLAS3D sample, we correlate the presence or lack of cores with stellar kinematics, including the proxy for the stellar angular momentum and the velocity dispersion within one half-light radius, stellar mass, stellar age, $\alpha$-element abundance, and age and metallicity gradients. More than half of the slow rotators have core-less light profiles, and they are all less massive than $10^{11}$ Msun. Core-less slow rotators show evidence for counter-rotating flattened structures, have steeper metallicity gradients, and a larger dispersion of gradient values than core slow rotators. Our results suggest that core and core-less slow rotators have different assembly processes, where the former are the relics of massive dissipation-less merging in the presence of central supermassive black holes. Formation processes of core-less slow rotators are consistent with accretion of counter-rotating gas or gas-rich mergers of special orbital configurations, which lower the final net angular momentum of stars, but support star formation. We also highlight core fast rotators as galaxies that share properties of core slow rotators and core-less slow rotators. Formation processes similar to those for core-less slow rotators can be invoked to explain the assembly of core fast rotators, with the distinction that these processes form or preserve cores.[Abridged]

[40]  arXiv:2001.11290 [pdf, ps, other]
Title: Intra-night flickering of RS Ophiuchi: III. Modes of quasi-periods in the minute scale and their evolution
Comments: accepted for publication in Bulgarian Astronomical Journal
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

We study the photometric behavior of the recurrent nova RS Oph by 58 monitoring light curves (LCs), taken by 5 telescopes. All LCs show repeating time structures with some quasi-periods (QPs) in time scales from minutes to hours. In our previous work 97 QPs were detected in the LCs by local minimums of structure functions and local maximums of auto-correlation functions. The distribution of the QPs shows modes at 8, 13, 21, 30, 48 and 73 min, where the mode at 8 min is poorly unveiled. These modes follow a power function with base $1.55\approx 3/2$ with standard deviation 4.7%. This function predicts modes also at 5.3 and 3.5 min, which are not detected in the full MLCs. In the present work we analyze simple small parts from high resolution LCs. We confirm the QPs modes at 8.0, 5.3 and 3.5 min. Generally, we found 8 QP modes with regular logarithmic distribution in the time interval 3.5-73 min. We also show typical intra-night evolutions of QP modes in the minute scale -- sharp or gradual transitions from one QP mode to other. In the end we find that the parts of the LCs carry out the properties of the whole LCs at short time scale. This lead to two well pronounces dependences - between the range deviation and standard deviation of the LC, as well as between the quasi-period and the relevant level of the density function of the LC.

[41]  arXiv:2001.11294 [pdf, other]
Title: First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey: The Effect of Host Galaxy Properties on Supernova Luminosity
Comments: 27 pages, 13 figures; Submitted to MNRAS
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

We present improved photometric measurements for the host galaxies of 206 spectroscopically confirmed type Ia supernovae discovered by the Dark Energy Survey Supernova Program (DES-SN) and used in the first DES-SN cosmological analysis. Fitting spectral energy distributions to the $griz$ photometric measurements of the DES-SN host galaxies, we derive stellar masses and star-formation rates. For the DES-SN sample, when considering a 5D ($z$, $x_1$, $c$, $\alpha$, $\beta$) bias correction, we find evidence of a Hubble residual `mass step', where SNe Ia in high mass galaxies ($>10^{10} \textrm{M}_{\odot}$) are intrinsically more luminous (after correction) than their low mass counterparts by $\gamma=0.040\pm0.019$mag. This value is larger by $0.031$mag than the value found in the first DES-SN cosmological analysis. This difference is due to a combination of updated photometric measurements and improved star formation histories and is not from host-galaxy misidentification. When using a 1D (redshift-only) bias correction the inferred mass step is larger, with $\gamma=0.066\pm0.020$mag. The 1D-5D $\gamma$ difference for DES-SN is $0.026\pm0.009$mag. We show that this difference is due to a strong correlation between host galaxy stellar mass and the $x_1$ component of the 5D distance-bias correction. To better understand this effect, we include an intrinsic correlation between light-curve width and stellar mass in simulated SN Ia samples. We show that a 5D fit recovers $\gamma$ with $-9$mmag bias compared to a $+2$mmag bias for a 1D fit. This difference can explain part of the discrepancy seen in the data. Improvements in modeling correlations between galaxy properties and SN is necessary to determine the implications for $\gamma$ and ensure unbiased precision estimates of the dark energy equation-of-state as we enter the era of LSST.

[42]  arXiv:2001.11299 [pdf, ps, other]
Title: Simulating Kilonovae in the ΛCDM Universe
Comments: 13 pages, 11 figures, submitted to MNRAS
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Kilonovae are optical flashes produced in the aftermath of neutron star-neutron star mergers (NNMs) or neutron star-black hole mergers (NBMs). In this work, we use the Millennium Simulation, combined with a semi-analytic galaxy formation model--GABE (Galaxy Assembly with Binary Evolution) which adopts binary stellar population synthesis models, to explore the cosmic event rate of kilonovae, and the properties of their host galaxies in a cosmological context. We find that model with supernova kick velocity of 0 km/s fits the observation best, in agreement with the exception of some formation channels of binary neutron star. This indicates that NNMs prefer to originate from binary systems with low kick velocities. With V$_{\rm kick}$=0 km/s, the cosmic event rate of NNMs and NBMs at z=0 are 283 Gpc$^{-3}$yr$^{-1}$ and 91 Gpc$^{-3}$yr$^{-1}$, respectively, marginally consistent with the constraint from LVC GWTC-1. For Milky Way-mass galaxies, we predict the NNM rate is $25.7^{+59.6}_{-7.1}$ Myr$^{-1}$, which is also in good agreement with the observed properties of binary neutron stars in the Milky Way. Taking all the NNMs into account in the history of Milky Way-mass galaxies, we find that the averaged r-process elements yield with A>79 in a NNM and NBM event should be 0.01 M$_{\odot}$ to be consistent with observation. We conclude that NGC 4993, the host galaxy of GW170817, is a typical host galaxy for NNMs. However, generally NNMs and NBMs tend to reside in young, blue, star-forming, late-type galaxies, with stellar mass and gaseous metallicity distribution peaking at $10^{10.65}$ M$_{\odot}$ and 8.72-8.85, respectively. By studying kilonovae host galaxies in the cosmological background, it is promising to constrain model details better when we have more events in the forthcoming future. (abridged)

[43]  arXiv:2001.11319 [pdf, other]
Title: Spectroscopic orbits of three dwarf barium stars
Authors: P. L. North (1), A. Jorissen (2), A. Escorza (2,3), B. Miszalski (4,5), J. Mikolajewska (6) ((1) Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, (2) Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, Belgium, (3) Instituut voor Sterrenkunde, KU Leuven, Belgium, (4) South African Astronomical Observatory, (5) Southern African Large Telescope Foundation, (6) N. Copernicus Astronomical Center, Warsaw, Poland)
Comments: 15 pages, 5 figures, to be published in The Observatory
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)

Barium stars are thought to result from binary evolution in systems wide enough to allow the more massive component to reach the asymptotic giant branch and eventually become a CO white dwarf. While Ba stars were initially known only among giant or subgiant stars, some were subsequently discovered also on the main sequence (and known as dwarf Ba stars). We provide here the orbital parameters of three dwarf Ba stars, completing the sample of 27 orbits published recently by Escorza et al. with these three southern targets. We show that these new orbital parameters are consistent with those of other dwarf Ba stars.

[44]  arXiv:2001.11344 [pdf, ps, other]
Title: Detection of vibrational emissions from the helium hydride ion (HeH$^+$) in the planetary nebula NGC 7027
Authors: David A. Neufeld (JHU), Miwa Goto (LMU), T. R. Geballe (Gemini), Rolf Güsten (MPIfR), Karl M. Menten (MPIfR), Helmut Wiesemeyer (MPIfR)
Comments: 49 pages, including 17 figures. Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)

We report the detection of emission in the v=1-0 P(1) (3.51629 micron) and P(2) (3.60776 micron) rovibrational lines of the helium hydride cation (HeH+) from the planetary nebula NGC 7027. These detections were obtained with the iSHELL spectrograph on NASA's Infrared Telescope Facility (IRTF) on Maunakea. The confirm the discovery of HeH+ reported recently by Guesten et al. (2019), who used the GREAT instrument on the SOFIA airborne observatory to observe its pure rotational J=1-0 transition at 149.137 micron. The flux measured for the HeH+ v=1-0 P(1) line is in good agreement with our model for the formation, destruction and excitation of HeH+ in NGC 7027. The measured strength of the J=1-0 pure rotational line, however, exceeds the model prediction significantly, as does that of the v=1-0 P(2) line, by factors of 2.9 and 2.3 respectively. Possible causes of these discrepancies are discussed. Our observations of NGC 7027, covering the 3.26 - 3.93 micron spectral region, have led to the detection of more than sixty spectral lines including nine rovibrational emissions from CH+. The latter are detected for the first time in an astronomical source.

[45]  arXiv:2001.11361 [pdf, other]
Title: 2018 NASA Laboratory Astrophysics Workshop: Scientific Organizing Committee Report
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

This report provides detailed findings on the critical laboratory astrophysics data needs that are required to maximize the scientific return for NASA's current and near-term planned astrophysics missions. It also provides prioritized rankings on said laboratory astrophysics data, generally by waveband. The Report is based on community input gathered at the 2018 NASA Laboratory Astrophysics Workshop (LAW) from presentations, from discussions during workshop breakout sessions, and from other solicited input deemed appropriate by the Scientific Organizing Committee (SOC) obtained prior to and after the meeting. Hence, the Report is a direct reflection of the spirit and participant make-up of LAW 2018. The Report also outlines specific opportunities and threats facing NASA's Laboratory Astrophysics Program, and articulates concrete actions by which the Agency can capitalize on the opportunities and mitigate the challenges. The Report was prepared by the SOC, with help from some invited speakers, and input and review from community members.

[46]  arXiv:2001.11378 [pdf, other]
Title: Site testing campaign for the Large Optical/infrared Telescope of China: Overview
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

The Large Optical/infrared Telescope (LOT) is a ground-based 12m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade. Based on satellite remote sensing data, along with geographical, logistical and political considerations, three candidate sites were chosen for ground-based astronomical performance monitoring. These sites include: Ali in Tibet, Daocheng in Sichuan, and Muztagh Ata in Xinjiang. Up until now, all three sites have continuously collected data for two years. In this paper, we will introduce this site testing campaign, and present its monitoring results obtained during the period between March 2017 and March 2019.

[47]  arXiv:2001.11405 [pdf, other]
Title: Lense-Thirring frame dragging induced by a fast-rotating white dwarf in a binary pulsar system
Comments: Accepted for publication in Science
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)

Radio pulsars in short-period eccentric binary orbits can be used to study both gravitational dynamics and binary evolution. The binary system containing PSR J1141$-$6545 includes a massive white dwarf (WD) companion that formed before the gravitationally bound young radio pulsar. We observe a temporal evolution of the orbital inclination of this pulsar that we infer is caused by a combination of a Newtonian quadrupole moment and Lense-Thirring precession of the orbit resulting from rapid rotation of the WD. Lense-Thirring precession, an effect of relativistic frame-dragging, is a prediction of general relativity. This detection is consistent with the evolutionary scenario in which the WD accreted matter from the pulsar progenitor, spinning up the WD to a period $< 200$ seconds.

[48]  arXiv:2001.11410 [pdf, other]
Title: The Tucana dwarf spheroidal galaxy: not such a massive failure after all
Comments: 26 pages, 9 figures, accepted to A&A
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Isolated Local Group (LG) dwarf galaxies have evolved most or all of their life unaffected by interactions with the large LG spirals and therefore offer the opportunity to learn about the intrinsic characteristics of this class of objects. Here we explore the internal kinematic and metallicity properties of one of the three isolated LG dwarf spheroidal galaxies, i.e. the Tucana dSph. This is an intriguing system, as it has been found in the literature to have an internal rotation of up to 16 km/s, a much higher velocity dispersion than other dSphs of similar luminosity, and a possible exception to the too-big-too-fail problem. We present results for a new VLT/FORS2 spectroscopic dataset in the CaII triplet region for 50 candidate red giant branch stars in the direction of Tucana, which yielded line-of-sight velocity and metallicity ([Fe/H]) measurements of 39 effective members. This doubles the number of Tucana's stars with such measurements. In addition, we re-reduce and include in our analysis the other two spectroscopic datasets presented in the literature, the VLT/FORS2 sample by Fraternali et al. (2009) and the VLT/FLAMES one by Gregory et al. (2019). We measure a systemic velocity of $180.0\pm1.3$ km/s, consistently across the various datasets analyzed, and find that a dispersion-only model is moderately favored over models accounting also for internal rotation. Our best estimate of the internal velocity dispersion is $6.2_{-1.3}^{+1.6}$ km/s, much smaller than the values reported in the literature and in line with similarly luminous dSphs; this is consistent with Tucana not being an exception to the too-big-to-fail problem, nor living in a dark matter halo much more massive than those of its siblings. As for the metallicity properties, we do not find anything unusual; there are hints of the presence of a [Fe/H] gradient but more data are needed to pin its presence down.

[49]  arXiv:2001.11418 [pdf, ps, other]
Title: The Nature of the Double Nuclei in the Barred S0 Galaxy IC676
Comments: 15 pages, 7 figures, accepted by ApJ. Comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA)

The lenticular galaxy IC 676 is a barred galaxy with double nuclei and active star formation in the central region. In this work we present the long-slit spectroscopy and archival multi-wavelength images to investigate the nature and origin of the double nuclei in IC 676. Through photometric 1D brightness profiles and 2D image decomposition, we show that this galaxy consists of a stellar bar with the length of $\sim$ 2.5 kpc and two S\'ersic disks both of which with S\'ersic index $\it n \sim$ 1.3. There is probably little or no bulge component assembled in IC 676. The luminosities of the double nuclei are primarily dominated by young stellar populations within the ages of 1-10 Myr. The northern nucleus has stronger star formation activity than the southern one. The surface densities of the star formation rate in the double nuclei are similar to those in starburst galaxies or the circumnuclear star forming regions in spiral galaxies. Each of the double nuclei in IC 676 likely consists of young massive star clusters, which can be resolved as bright knots in the HST high resolution image. Our results suggest that IC 676 likely has a complex formation and evolutionary history. The secular processes driven by the stellar bar and external accretion may dominate the formation and evolution of its double nuclei. This indicates that the secular evolution involving the internal and external drivers may have an important contribution for the evolution of lenticular galaxies.

[50]  arXiv:2001.11420 [pdf, other]
Title: Hints of dark energy anisotropic stress using Machine Learning
Comments: 13 pages, 5 figures, 2 tables, comments welcome
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

Recent analyses of the Planck data and quasars at high redshifts have suggested possible deviations from the flat $\Lambda$ cold dark matter model ($\Lambda$CDM), where $\Lambda$ is the cosmological constant. Here, we use machine learning methods to investigate any possible deviations from $\Lambda$CDM at both low and high redshifts by using the latest cosmological data. Specifically, we apply the genetic algorithms to explore the nature of dark energy (DE) in a model independent fashion by reconstructing its equation of state $w(z)$, the growth index of matter density perturbations $\gamma(z)$, the linear DE anisotropic stress $\eta_{DE}(z)$ and the adiabatic sound speed $c_{s,DE}^2(z)$ of DE perturbations. We find a $\sim2\sigma$ deviation of $w(z)$ from -1 at high redshifts, the adiabatic sound speed is negative at the $\sim2\sigma$ level and a $\sim3\sigma$ deviation of the anisotropic stress from unity at low redshifts and $\sim3.5 \sigma$ at high redshifts. These results suggest either the presence of a strong non-adiabatic component in the DE sound speed or the presence of DE anisotropic stress, thus hinting at possible deviations from the $\Lambda$CDM model.

[51]  arXiv:2001.11444 [pdf, other]
Title: Implications of three-dimensional chemical transport in hot Jupiter atmospheres: results from a consistently coupled chemistry-radiation-hydrodynamics model
Comments: Re-submitted to A&A following the first referee report
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We present results from a set of simulations using a fully coupled three-dimensional (3D) chemistry-radiation-hydrodynamics model and investigate the effect of transport of chemical species by the large-scale atmospheric flow in hot Jupiter atmospheres. We couple a flexible chemical kinetics scheme to the Met Office Unified Model which enables the study of the interaction of chemistry, radiative transfer and fluid dynamics. We use a newly-released "reduced" chemical network comprising 30 chemical species that has been specifically developed for application in 3D atmosphere models. We simulate the atmospheres of the well-studied hot Jupiters HD~209458b and HD~189733b which both have dayside--nightside temperature contrasts of several hundred Kelvin and superrotating equatorial jets. We find qualitatively quite different chemical structures between the two planets, particularly for methane (CH$_4$), when advection of chemical species is included. Our results show that consideration of 3D chemical transport is vital in understanding the chemical composition of hot Jupiter atmospheres. 3D mixing leads to significant changes in the abundances of absorbing gas-phase species compared with what would be expected by assuming local chemical equilibrium, or from models including 1D - and even 2D - chemical mixing. We find that CH$_4$, carbon dioxide (CO$_2$) and ammonia (NH$_3$) are particularly interesting as 3D mixing of these species leads to prominent signatures of out-of-equilibrium chemistry in the transmission and emission spectra, detectable with near-future instruments.

[52]  arXiv:2001.11445 [pdf, ps, other]
Title: IGRINS Slit-Viewing Camera Software
Authors: Hye-In Lee
Comments: 29 pages
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We have developed observation control software for the Immersion GRating INfrared Spectrometer (IGRINS) slit-viewing camera module, which maintains the position of an astronomical target on the spectroscopic slit. It is composed of several packages that monitor and control the system, acquire the images, and compensate for the tracking error by sending tracking feedback information to the telescope control system. For efficient development and maintenance of each software package, we have applied software engineering methods, i.e., a spiral software development with model-based design. It is not trivial to define the shape and center of astronomical object point spread functions (PSFs), which do not have symmetric Gaussian profiles in short exposure (<4 s) guiding images. Efforts to determine the PSF centroid are additionally complicated by the core saturation of bright guide stars. We have applied both a two-dimensional Gaussian fitting algorithm (2DGA) and center balancing algorithm (CBA) to identify an appropriate method for IGRINS in the near-infrared K-band. The CBA derives the expected center position along the slit-width by referencing the spillover flux ratio of the PSF wings on both sides of the slit. In this research, we have compared the accuracy and reliability of the CBA to the 2DGA by using data from IGRINS commissioning observations at McDonald Observatory. We find that the performance of each algorithm depends on the brightness of the targets and the seeing conditions, with the CBA performing better in typical observing scenarios. The algorithms and test results we present can be utilized with future spectroscopic slit observations in various observing conditions and for a variety of spectrograph designs.

[53]  arXiv:2001.11470 [pdf, other]
Title: Distinguishing high-mass binary neutron stars from binary black holes with second- and third-generation gravitational wave observatories
Comments: 18 pages, 10 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)

(Abridged) While the gravitational-wave (GW) signal GW170817 was accompanied by a variety of electromagnetic (EM) counterparts, sufficiently high-mass binary neutron star (BNS) mergers are expected to be unable to power bright EM counterparts. The putative high-mass binary BNS merger GW190425, for which no confirmed EM counterpart has been identified, may be an example of such a system. It is thus important to understand how well we will be able to distinguish high-mass BNSs and low-mass binary black holes (BBHs) solely from their GW signals. To do this, we consider the imprint of the tidal deformability of the neutron stars on the GW signal for systems undergoing prompt black hole formation after merger. We model the BNS signals using hybrid numerical relativity -- tidal effective-one-body waveforms. Specifically, we consider a set of five nonspinning equal-mass BNS signals with masses of 2.7, 3.0, 3.2 Msun and with three different equations of state, as well as the analogous BBH signals. We perform parameter estimation on these signals in three networks: Advanced LIGO-Advanced Virgo and Advanced LIGO-Advanced Virgo-KAGRA with sensitivities similar to O3 and O4, respectively, and a 3G network of two Cosmic Explorers (CEs) and one Einstein Telescope, with a CE sensitivity similar to Stage 2. Our analysis suggests that we cannot distinguish the signals from high-mass BNSs and BBHs at a 90% credible level with the O3-like network even at 40 Mpc. However, we can distinguish all but the most compact BNSs that we consider in our study from BBHs at 40 Mpc at a >= 95% credible level using the O4-like network, and can even distinguish them at a > 99.2% (>= 97%) credible level at 369 (835) Mpc using the 3G network. Additionally, we present a simple method to compute the leading effect of the Earth's rotation on the response of a gravitational wave detector in the frequency domain.

[54]  arXiv:2001.11491 [pdf, ps, other]
Title: Narrow lines correlations in an SDSS sample of type 1 quasars
Authors: I. Jankov, D. Ilić
Comments: 10 pages, 4 figures, 1 table. Proceedings of 12th Serbian Conference on Spectral Line Shapes in Astrophysics
Journal-ref: Contributions of the Astronomical Observatory Skalnate Pleso, 50, 2020, 350-359
Subjects: Astrophysics of Galaxies (astro-ph.GA)

Investigation of quasar emission line properties and relationships between spectral parameters is important for understanding the physical mechanisms that originate inside different regions of the active galactic nuclei. In this paper, we investigate the optical spectral parameters of type 1 quasars taken from the Sloan Digital Sky Survey Data Release 7 Quasar Catalog (arXiv:1006.5178 [astro-ph.CO]). Spectral parameters, such are equivalent widths and full widths at half maximum of both narrow and broad lines are taken into account. We perform the analysis of correlation matrix and principal component analysis of our sample. We obtain that the narrow line Baldwin effect is significant enough and deserves further investigation. We provide the correlation coefficients and slope values for Baldwin effect in several narrow lines.

[55]  arXiv:2001.11504 [pdf, other]
Title: Constraining galactic structures of mirror dark matter
Comments: 30 pages, 8 figures
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)

The simplest model of mirror sector dark matter maintains exact mirror symmetry, but has a baryon abundance $\Omega_{b'} = \beta \Omega_b$ and a suppressed temperature $T' = x T$ in the mirror sector; hence it depends only on two parameters, $\beta,x$. For sufficiently small $x$, early cosmological observables may not constrain mirror baryons from constituting all of the dark matter despite their strong self-interactions, depending on the unknown details of structure formation in the hidden sector. Here we close this loophole by simulating mirror structure formation, mapping out the allowed regions of parameter space using cosmological and astronomical data. We find that the Milky Way disk surface density and bulge mass constrain $\Omega_{b'}\lesssim 0.3 \Omega_{b}$ at the highest $T'$ allowed by BBN and CMB ($T'=0.5 T$), or $\Omega_{b'}\lesssim 0.8 \Omega_{b}$ at lower values of $T'$. We also briefly discuss the realization of the necessary temperature asymmetry between the SM and the mirror sector in our model with unbroken mirror symmetry.

Cross-lists for Fri, 31 Jan 20

[56]  arXiv:2001.11380 (cross-list from physics.space-ph) [pdf, other]
Title: Kinetic models of tangential discontinuities in the solar wind
Comments: 11 pages, 6 figures, accepted for publication in ApJ
Subjects: Space Physics (physics.space-ph); Solar and Stellar Astrophysics (astro-ph.SR)

Kinetic-scale current sheets observed in the solar wind are frequently approximately force-free despite the fact that their plasma $\beta$ is of the order of one. In-situ measurements have recently shown that plasma density and temperature often vary across the current sheets, while the plasma pressure is approximately uniform. In many cases these density and temperature variations are asymmetric with respect to the center of the current sheet. To model these observations theoretically we develop in this paper equilibria of kinetic-scale force-free current sheets that have plasma density and temperature gradients. The models can also be useful for analysis of stability and dissipation of the current sheets in the solar wind.

[57]  arXiv:2001.11387 (cross-list from gr-qc) [pdf]
Title: Cosmological models from a geometric point of view
Authors: M.A.H. MacCallum
Comments: These notes have been widely cited, but were not readily available. The copyright is held by Taylor and Francis who now own Gordon and Breach and whose permission must be sought for any uses demanding copyright. They have given permission for posting to archives, for which I am grateful, saying "Given that the material was pre-digital you are permitted to scan and post the printed original."
Journal-ref: Carg\`ese Lectures in Physics, vol.6, ed. E. Schatzman, pages 61-174. Gordon and Breach, New York (1973)
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

(There is no original abstract.) These are lecture notes from a 1971 summer school surveying the then known cosmological models in particular the properties of Bianchi cosmologies, and giving a pedagogical introduction to groups of isometries in spacetime and to the orthonormal tetrad method.

[58]  arXiv:2001.11412 (cross-list from gr-qc) [pdf, other]
Title: Setting the cornerstone for the IMRPhenomX family of models for gravitational waves from compact binaries: The dominant harmonic for non-precessing quasi-circular black holes
Comments: 29 pages. 20 figures. Comments and feedback welcome! This paper corresponds to LIGO DCC P2000018
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

In this paper we present IMRPhenomXAS, a thorough overhaul of the IMRPhenomD [1,2] waveform model, which describes the dominant $l=2, \:| m | = 2$ spherical harmonic mode of non-precessing coalescing black holes in terms of piecewise closed form expressions in the frequency domain. Improvements include in particular the accurate treatment of unequal spin effects, and the inclusion of extreme mass ratio waveforms. IMRPhenomD has previously been extended to approximately include spin precession [3] and subdominant spherical harmonics [4], and with its extensions it has become a standard tool in gravitational wave parameter estimation. Improved extensions of IMRPhenomXAS are discussed in companion papers [5,6].

[59]  arXiv:2001.11484 (cross-list from gr-qc) [pdf, other]
Title: Numerical investigation of plasma-driven superradiant instabilities
Comments: 22 pages, 8 figures. To be submitted to JCAP
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

Photons propagating in a plasma acquire an effective mass $\mu$, which is given by the plasma frequency and which scales with the square root of the plasma density. As noted previously by Conlon and Herdeiro, for electron number densities $n_e\sim 10^{-3}$ cm$^{-3}$ (such as those measured in the interstellar medium) the effective mass induced by the plasma is $\mu \sim 10^{-12}$ eV. This would cause superradiant instabilities for spinning black holes of a few tens of solar masses. An obvious problem with this picture is that densities in the vicinity of black holes are much higher than in the interstellar medium because of accretion. We have conducted numerical simulations of the superradiant instability in spinning black holes surrounded by a plasma with density increasing closer to the black hole, in order to mimic the effect of accretion. While we confirm that superradiant instabilities appear for plasma densities that are sufficiently low near the black hole, we find that astrophysically realistic accretion disks are unlikely to trigger such instabilities.

[60]  arXiv:2001.11503 (cross-list from physics.flu-dyn) [pdf, other]
Title: The generation and sustenance of electric fields in sandstorms
Comments: 4 pages, 5 figures, submitted to Physical Review Letters (PRL), American Physical Society
Subjects: Fluid Dynamics (physics.flu-dyn); Earth and Planetary Astrophysics (astro-ph.EP); Computational Physics (physics.comp-ph)

Sandstorms are frequently accompanied by the generation of intense electric fields and lightning. In a very narrow region close to the ground level, sand particles undergo a charge exchange mechanism whereby larger (resp. smaller) sized sand grains become positively (resp. negatively) charged are then entrained by the turbulent fluid motion. Our central hypothesis is that differently sized sand particles get differentially transported by the turbulent flow resulting in a large-scale charge separation, and hence a large-scale electric field. We utilize our simulation framework, comprising of large-eddy simulation of the turbulent atmospheric boundary layer along with sand particle transport and an electrostatic Poisson solver, to investigate the physics of electric fields in sandstorms and thus, to confirm our hypothesis. We utilize the simulation framework to investigate electric fields in weak to strong sandstorms that are characterized by the number density of the sand particles. Our simulations reproduce observational measurements of both mean and RMS fluctuation values of the electric field. We propose a scaling law in which the electric field scales as the two-thirds power of the number density that holds for weak-to-medium sandstorms.

[61]  arXiv:2001.11505 (cross-list from hep-ph) [pdf, other]
Title: A little theory of everything, with heavy neutral leptons
Comments: 25 pages, 6 figures
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Recently a new model of "Affleck-Dine inflation" was presented, that produces the baryon asymmetry from a complex inflaton carrying baryon number, while being consistent with constraints from the cosmic microwave background. We adapt this model such that the inflaton carries lepton number, and communicates the lepton asymmetry to the standard model baryons via quasi-Dirac heavy neutral leptons (HNLs) and sphalerons. One of these HNLs, with mass $\lesssim 4.5\,$GeV, can be (partially) asymmetric dark matter (DM), whose asymmetry is determined by that of the baryons. Its stability is directly related to the vanishing of the lightest neutrino mass. Neutrino masses are generated by integrating out heavy sterile neutrinos whose mass is above the inflation scale. The model provides an economical origin for all of the major ingredients missing from the standard model: inflation, baryogenesis, neutrino masses, and dark matter. The HNLs can be probed in fixed-target experiments like SHiP, possibly manifesting $N$-$\bar N$ oscillations. A light singlet scalar, needed for depleting the DM symmetric component, can be discovered in beam dump experiments and searches for rare decays, possibly explaining anomalous events recently observed by the KOTO collaboration. The DM HNL is strongly constrained by direct searches, and could have a cosmologically interesting self-interaction cross section.

Replacements for Fri, 31 Jan 20

[62]  arXiv:1810.11561 (replaced) [pdf, other]
Title: Mass Measurements of Neutron-Rich Gallium Isotopes Refine Production of Nuclei of the First r-Process Abundance Peak in Neutron Star Merger Calculations
Subjects: Nuclear Experiment (nucl-ex); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
[63]  arXiv:1901.11033 (replaced) [pdf, other]
Title: Metric Gaussian Variational Inference
Comments: Code is part of NIFTy5 release at this https URL
Subjects: Machine Learning (stat.ML); Instrumentation and Methods for Astrophysics (astro-ph.IM); Machine Learning (cs.LG); Data Analysis, Statistics and Probability (physics.data-an); Methodology (stat.ME)
[64]  arXiv:1902.02291 (replaced) [pdf, other]
Title: Characterizing the Gamma-Ray Variability of the Brightest Flat Spectrum Radio Quasars Observed with the Fermi LAT
Comments: Accepted for publication in ApJ. 37 pages, 17 Figures, 8 Tables; minor typos corrected
Journal-ref: The Astrophysical Journal 2019, Volume 877, Number 1
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
[65]  arXiv:1903.11622 (replaced) [pdf, other]
Title: Black-hole remnants from black-hole--neutron-star mergers
Journal-ref: Phys. Rev. Lett. 123, 041102 (2019)
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[66]  arXiv:1905.00314 (replaced) [pdf, other]
Title: Prospects of joint detections of neutron star mergers and short-GRBs with Gaussian structured jets
Authors: M. Saleem
Comments: 8 pages, 2 figures, 1 table. (Accepted for publication in MNRAS)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[67]  arXiv:1908.07227 (replaced) [pdf, other]
Title: Force-free electrodynamics near rotation axis of a Kerr black hole
Comments: 10 pages. v3: Discussion of the outer light surface expanded considerably. Assumptions are clarified
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
[68]  arXiv:1909.00405 (replaced) [pdf, other]
Title: Constraining the properties of gaseous halos via cross-correlations of upcoming galaxy surveys and thermal Sunyaev-Zel'dovich maps
Comments: 18 pages, 10 figures. Comments welcome. Change in the halo mass uncertainty resulting in very minor change in relevant figures, no change to any conclusions
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
[69]  arXiv:1909.05966 (replaced) [pdf, other]
Title: Learning Bayesian posteriors with neural networks for gravitational-wave inference
Comments: (Superior-to-)published version; source code and trained networks available at this https URL
Journal-ref: Phys. Rev. Lett. 124, 041102 (2020)
Subjects: General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Methods for Astrophysics (astro-ph.IM); Machine Learning (stat.ML)
[70]  arXiv:1909.06755 (replaced) [pdf, ps, other]
Title: ISCOs and OSCOs in the presence of positive cosmological constant
Authors: Petarpa Boonserm (Chulalongkorn University, Thailand Center of Excellence in Physics), Tritos Ngampitipan (Chandrakasem Rajabhat University, Thailand Center of Excellence in Physics), Alex Simpson (Victoria University of Wellington), Matt Visser (Victoria University of Wellington)
Comments: V1: 14 pages; V2: four references added, minor rephrasing, no change in physics conclusions; V3: now 20 pages; four more references added; extra discussion regarding Paczynski-Wiita potential and Jeans scale. Closely corresponds to published version
Journal-ref: Physical Review D 101 # 2 (2020) 024050
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA)
[71]  arXiv:1910.00590 (replaced) [pdf, other]
Title: Beyond optical depth: Future determination of ionization history from the CMB
Comments: 13 pages, 10 figures, matches version accepted by ApJ, corrected author information
Journal-ref: The Astrophysical Journal, February 1 2020, Volume 889, Number 2
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[72]  arXiv:1910.06970 (replaced) [pdf, ps, other]
Title: High-z dusty star-forming galaxies: a top-heavy initial mass function?
Comments: ApJ accepted
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[73]  arXiv:1911.00341 (replaced) [pdf, other]
Title: Fat brane, dark matter and localized kinetic terms in six dimensions
Comments: 12 pages, 6 figures, 2 tables, references added, version accepted for publication in EPJC
Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[74]  arXiv:1911.06447 (replaced) [pdf, other]
Title: Radio/X-ray Correlation in the Mini-Outburts of Black Hole X-ray Transient GRS 1739--278
Comments: 11 pages, 5 figures and 1 table. ApJ accepted
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[75]  arXiv:1911.09469 (replaced) [pdf, other]
Title: Generalized covariant prescriptions for averaging cosmological observables
Comments: 29 pages, 7 figures. Several comments added, comparison with previous results improved, references added. Version accepted for publication on JCAP
Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
[76]  arXiv:1911.11959 (replaced) [pdf, other]
Title: Characterising the Structure of Halo Merger Trees Using a Single Parameter: The Tree Entropy
Comments: 20 pages, 18 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Combinatorics (math.CO)
[77]  arXiv:1911.12772 (replaced) [pdf, ps, other]
Title: Incoherent fast variability of X-ray obscurers. The case of NGC 3783
Comments: Accepted for publication in A&A, corrected typo in Fig. 8
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[78]  arXiv:1911.12832 (replaced) [pdf, other]
Title: A lack of evolution in the very bright-end of the galaxy luminosity function from z = 8-10
Comments: Updated to match MNRAS accepted version (accepted 27/01/2020) after minor revisions. 18 pages, 10 figures and 7 tables in the main text, plus additional figures in the appendix
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
[79]  arXiv:1912.00526 (replaced) [pdf, ps, other]
Title: Fast Radio Bursts Not Made By Neutron Stars
Authors: J. I. Katz
Comments: 4 pp Revised with expanded discussion of absence of Galactic micro-FRB and periodicity of FRB 180916.J0158+65
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
[80]  arXiv:1912.02199 (replaced) [pdf, ps, other]
Title: The dynamical history of the evaporating or disrupted ice giant planet around white dwarf WD J0914+1914
Comments: Accepted for publication in MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
[81]  arXiv:1912.05927 (replaced) [pdf, other]
Title: Scalar induced gravitational waves in inflation with gravitationally enhanced friction
Comments: 17 pages, 5 figures, 1 table
Journal-ref: Phys. Rev. D 101, 023529 (2020)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
[82]  arXiv:2001.01093 (replaced) [pdf, other]
Title: Testing the solar activity paradigm in the context of exoplanet transits
Comments: Accepted for publication in the Astrophysical Journal. Version corrected to match paper in print
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
[83]  arXiv:2001.01730 (replaced) [pdf, ps, other]
Title: Upper Limit on the Dissipation of Gravitational Waves in Gravitationally Bound Systems
Authors: Abraham Loeb (Harvard)
Comments: 5 pages, submitted to The Astrophysical Journal Letters
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
[84]  arXiv:2001.06492 (replaced) [pdf, other]
Title: On the origin of GW190425
Comments: Submitted, 7 pages, 3 figures
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
[85]  arXiv:2001.09985 (replaced) [pdf, other]
Title: Contribution of pulsars to cosmic-ray positrons in light of recent observation of inverse-Compton halos
Comments: 10 pages, 7 figures. Figures 2, 3 and 5 updated. Results unchanged
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
[86]  arXiv:2001.10004 (replaced) [pdf, other]
Title: Angular momentum profiles of Class 0 protostellar envelopes
Comments: Accepted for publication in Astronomy & Astrophysics
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
[87]  arXiv:2001.10538 (replaced) [pdf, other]
Title: A comprehensive catalog of dark matter halo models for SPARC galaxies
Comments: 11 pages, 6 figures, 1 table. Accepted for publication in ApJS
Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
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