Astrophysics

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New submissions for Wed, 4 Mar 20

[1]  arXiv:2003.01119 [pdf, other]

Title: Kraken reveals itself -- the merger history of the Milky Way reconstructed with the E-MOSAICS simulations

Authors: J. M. Diederik Kruijssen (1), Joel L. Pfeffer (2), Mélanie Chevance (1), Ana Bonaca (3), Sebastian Trujillo-Gomez (1), Nate Bastian (2), Marta Reina-Campos (1), Rob Crain (2), Meghan Hughes (2) ((1) Heidelberg, (2) LJMU, (3) Harvard)

Comments: 20 pages, 9 figures, 2 tables; submitted to MNRAS (March 1, 2020); Figures 4, 5, and 9 show the main results of the paper

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

Globular clusters (GCs) formed when the Milky Way experienced a phase of rapid assembly. We use the wealth of information contained in the Galactic GC population to quantify the properties of the satellite galaxies from which the Milky Way assembled. To achieve this, we train an artificial neural network on the E-MOSAICS cosmological simulations of the co-formation and co-evolution of GCs and their host galaxies. The network uses the ages, metallicities, and orbital properties of GCs that formed in the same progenitor galaxies to predict the stellar masses and accretion redshifts of these progenitors. We apply the network to Galactic GCs associated with five progenitors: {\it Gaia}-Enceladus, the Helmi streams, Sequoia, Sagittarius, and the recently discovered, `low-energy' GCs, which provide an excellent match to the predicted properties of the enigmatic galaxy `Kraken'. The five galaxies cover a narrow stellar mass range [$M_\star=(0.6{-}4.6)\times10^8~{\rm M}_\odot$], but have widely different accretion redshifts ($z_{\rm acc}=0.57{-}2.65$). All accretion events represent minor mergers, but Kraken likely represents the most major merger ever experienced by the Milky Way, with stellar and virial mass ratios of $r_{M_\star}=1$:$31^{+34}_{-16}$ and $r_{M_{\rm h}}=1$:$7^{+4}_{-2}$, respectively. The progenitors match the $z=0$ relation between GC number and halo virial mass, but have elevated specific frequencies, suggesting an evolution with redshift. Even though these progenitors likely were the Milky Way's most massive accretion events, they contributed a total mass of only $\log{(M_{\rm \star,tot}/{\rm M}_\odot)}=9.0\pm0.1$, similar to the stellar halo. This implies that the Milky Way grew its stellar mass mostly by in-situ star formation. We conclude by organising these accretion events into the most detailed reconstruction to date of the Milky Way's merger tree.

[2]  arXiv:2003.01120 [pdf, other]

Title: The expansion of stripped-envelope stars: consequences for supernovae and gravitational-wave progenitors

Authors: E. Laplace, Y. Götberg, S. E. de Mink, S. Justham, R. Farmer

Comments: Main text 17 pages, 7 figures, accepted for publication in Astronomy & Astrophysics

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

Massive binaries that merge as compact objects are the progenitors of gravitational-wave sources. Most of these binaries experience one or more phases of mass transfer, during which one of the stars loses part or all of its outer envelope and becomes a stripped-envelope star. The evolution of the size of these stripped stars is crucial in determining whether they experience further interactions and their final fate. We present new calculations of stripped-envelope stars based on binary evolution models computed with MESA. We use these to investigate their radius evolution as a function of mass and metallicity. We further discuss their pre-supernova observable characteristics and potential consequences of their evolution on the properties of supernovae from stripped stars. At high metallicity we find that practically all of the hydrogen-rich envelope is removed, in agreement with earlier findings. Only progenitors with initial masses below 10\Msun expand to large radii (up to 100\Rsun), while more massive progenitors stay compact. At low metallicity, a substantial amount of hydrogen remains and the progenitors can, in principle, expand to giant sizes (> 400\Rsun), for all masses we consider. This implies that they can fill their Roche lobe anew. We show that the prescriptions commonly used in population synthesis models underestimate the stellar radii by up to two orders of magnitude. We expect that this has consequences for the predictions for gravitational-wave sources from double neutron star mergers, in particular for their metallicity dependence.

[3]  arXiv:2003.01122 [pdf, other]

Title: A Semi-Automated Computational Approach for Infrared Dark Cloud Localization: A Catalog of Infrared Dark Clouds

Authors: Jyothish Pari, Joseph L. Hora

Comments: 17 pages, 18 figures, one machine-readable table. Accepted for publication in the PASP

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

The field of computer vision has greatly matured in the past decade, and many of the methods and techniques can be useful for astronomical applications. One example is in searching large imaging surveys for objects of interest, especially when it is difficult to specify the characteristics of the objects being searched for. We have developed a method using contour finding and convolution neural networks (CNNs) to search for Infrared Dark Clouds (IRDCs) in the Spitzer Galactic plane survey data. IRDCs can vary in size, shape, orientation, and optical depth, and are often located near regions with complex emission from molecular clouds and star formation, which can make the IRDCs difficult to reliably identify. False positives can occur in regions where emission is absent, rather than from a foreground IRDC. The contour finding algorithm we implemented found most closed figures in the mosaic and we developed rules to filter out some of the false positive before allowing the CNNs to analyze them. The method was applied to the Spitzer data in the Galactic plane surveys, and we have constructed a catalog of IRDCs which includes additional parts of the Galactic plane that were not included in earlier surveys.

[4]  arXiv:2003.01123 [pdf, other]

Title: Pre-Common-Envelope Mass Loss from Coalescing Binary Systems

Authors: Morgan MacLeod, Abraham Loeb

Comments: Submitted to AAS Journals, We welcome comments

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

Binary systems undergoing unstable Roche Lobe overflow spill gas into their circumbinary environment as their orbits decay toward coalescence. In this paper, we use a suite of hydrodynamic models of coalescing binaries involving an extended donor and a more compact accretor. We focus on the period of unstable Roche Lobe overflow that ends as the accretor plunges within the envelope of the donor at the onset of a common envelope phase. During this stage, mass is removed from the donor and flung into the circumbinary environment. Across a wide range of binary mass ratios, we find that the mass expelled as the separation decreases from the Roche limit to the donor's original radius is of the order of 25% of the accretor's mass. We study the kinematics of this ejecta and its dependencies on binary properties and find that it assembles into a toroidal circumbinary distribution. These circumbinary tori have approximately constant specific angular momentum due to momentum transport by spiral shocks launched from the orbiting binary. We show that an analytic model with these torus properties captures many of the main features of the azimuthally-averaged profiles of our hydrodynamic simulations. Our results, in particular the simple relationship between accretor mass and expelled mass and its spatial distribution, may be useful in interpreting stellar coalescence transients like luminous red novae, and in initializing hydrodynamic simulations of the subsequent common envelope phase.

[5]  arXiv:2003.01124 [pdf, other]

Title: A new method for deriving composition of S-type asteroids from noisy and incomplete near-infrared spectra

Authors: Juan A. Sanchez, Cristina Thomas, Vishnu Reddy, Noah Frere, Sean S. Lindsay, Adriana Mitchell

Comments: 22 pages, 11 figures, 2 tables, accepted for publication in The Astronomical Journal

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

The surface composition of S-type asteroids can be determined using band parameters extracted from their near-infrared (NIR) spectra (0.7-2.50 $\mu$m) along with spectral calibrations derived from laboratory samples. In the past, these empirical equations have been obtained by combining NIR spectra of meteorite samples with information about their composition and mineral abundance. For these equations to give accurate results, the characteristics of the laboratory spectra they are derived from should be similar to those of asteroid spectral data (i.e., similar signal-to-noise ratio (S/N) and wavelength range). Here we present new spectral calibrations that can be used to determine the mineral composition of ordinary chondrite-like S-type asteroids. Contrary to previous work, the S/N of the ordinary chondrite spectra used in this study has been decreased to recreate the S/N typically observed among asteroid spectra, allowing us to obtain more realistic results. In addition, the new equations have been derived for five wavelength ranges encompassed between 0.7 and 2.50 $\mu$m, making it possible to determine the composition of asteroids with incomplete data. The new spectral calibrations were tested using band parameters measured from the NIR spectrum of asteroid (25143) Itokawa, and comparing the results with laboratory measurements of the returned samples. We found that the spectrally derived olivine and pyroxene chemistry, which are given by the molar contents of fayalite (Fa) and ferrosilite (Fs), are in excellent agreement with the mean values measured from the samples (Fa$_{28.6\pm1.1}$ and Fs$_{23.1\pm2.2}$), with a maximum difference of 0.6 mol\% for Fa and 1.4 mol\% for Fs.

[6]  arXiv:2003.01125 [pdf, other]

Title: Towards a general parametrization of the warm dark matter halo mass function

Authors: Mark R. Lovell (University of Iceland)

Comments: 5 pages, 2 figures. To be submitted to ApJL. Contact: lovell@hi.is

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

Studies of flux anomalies statistics and perturbations in stellar streams have the potential to constrain models of warm dark matter (WDM), including sterile neutrinos. Producing these constraints requires a parametrization of the WDM mass function relative to that of the cold dark matter (CDM) equivalent. We use five WDM models with half-mode masses, $M_\mathrm{hm}=[1.3,35]\times10^{8}$~$M_{\odot}$, spread across simulations of the Local Group, lensing ellipticals and the $z=2$ universe, to generate such a parametrization: we fit parameters to the functional form $n_\mathrm{WDM}/n_\mathrm{CDM}=(1+(\alpha M_\mathrm{hm}/M_{X})^{\beta})^{\gamma}$. For $M_{X}\equiv$ virial mass of central halos we obtain $\alpha=2.3$, $\beta=0.8$, and $\gamma=-1.0$, and this fit is steeper than the EPS formalism predicts. For $M_{X}\equiv$ mass of subhalos we instead obtain $\alpha=4.2$, $\beta=2.5$ and $\gamma=-0.2$; in both mass definitions the scatter is $\sim20$ percent. However, we caution that robust constraints will require bespoke simulations and a careful definition of halo mass, particularly for subhalos of mass $<10^{8}M_{\odot}$.

[7]  arXiv:2003.01126 [pdf, other]

Title: A free-floating or wide-orbit planet in the microlensing event OGLE-2019-BLG-0551

Authors: P. Mroz, R. Poleski, C. Han, A. Udalski, A. Gould, M.K. Szymanski, I. Soszynski, P. Pietrukowicz, S. Kozlowski, J. Skowron, K. Ulaczyk, M. Gromadzki, K. Rybicki, P. Iwanek, M. Wrona, M.D. Albrow, S. Chung, K. Hwang, Y. Ryu, Y.K. Jung, I. Shin, Y. Shvartzvald, J.C. Yee, W. Zang, S. Cha, D. Kim, H. Kim, S. Kim, C. Lee, D. Lee, Y. Lee, B. Park, R.W. Pogge

Comments: submitted to AJ

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

High-cadence observations of the Galactic bulge by the microlensing surveys led to the discovery of a handful of extremely short-timescale microlensing events that can be attributed to free-floating or wide-orbit planets. Here, we report the discovery of another strong free-floating planet candidate, which was found from the analysis of the gravitational microlensing event OGLE-2019-BLG-0551. The light curve of the event is characterized by a very short duration (<3 d) and a very small amplitude (< 0.1 mag). From modeling of the light curve, we find that the Einstein timescale, tE = 0.381 +/- 0.017 d, is much shorter, and the angular Einstein radius, thetaE = 4.35 +/- 0.34 uas, is much smaller than those of typical lensing events produced by stellar-mass lenses (tE ~ 20 d, thetaE ~ 0.3 mas), indicating that the lens is very likely to be a planetary-mass object. We conduct an extensive search for possible signatures of a companion star in the light curve of the event, finding no significant evidence for the putative host star. For the first time, we also demonstrate that the angular Einstein radius of the lens does not depend on blending in the low-magnification events with strong finite source effects.

[8]  arXiv:2003.01127 [pdf, ps, other]

Title: Generating metal-polluting debris in white dwarf planetary systems from small-impact crater ejecta

Authors: Dimitri Veras, Kosuke Kurosawa

Comments: Accepted for publication in MNRAS

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

Metal pollution in white dwarf photospheres originates from the accretion of some combination of planets, moons, asteroids, comets, boulders, pebbles and dust. When large bodies reside in dynamically stagnant locations -- unable themselves to pollute nor even closely approach the white dwarf -- then smaller reservoirs of impact debris may become a complementary or the primary source of metal pollutants. Here, we take a first step towards exploring this possibility by computing limits on the recoil mass that escapes the gravitational pull of the target object following a single impact onto an atmosphere-less surface. By considering vertical impacts only with the full-chain analytical prescription from Kurosawa & Takada (2019), we provide lower bounds for the ejected mass for basalt, granite, iron and water-rich target objects across the radii range 10^{0-3} km. Our use of the full-chain prescription as opposed to physical experiments or hydrocode simulations allows us to quickly sample a wide range of parameter space appropriate to white dwarf planetary systems. Our numerical results could be used in future studies to constrain freshly-generated small debris reservoirs around white dwarfs given a particular planetary system architecture, bombardment history, and impact geometries.

[9]  arXiv:2003.01129 [pdf, other]

Title: Turbulent mixing of r-process elements in the Milky Way

Authors: Paz Beniamini, Kenta Hotokezaka

Comments: 10 pages, 10 figures

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

We study turbulent gas diffusion affects on the observed $r$-process abundances in Milky Way stars, by a combination of an analytical approach and a Monte Carlo simulation. Higher $r$-process event rates and faster diffusion, lead to more efficient mixing corresponding to a reduced scatter of $r$-process abundances and causing $r$-process enriched stars to start appearing at lower metallicity values. We use three independent observations to constrain the model parameters: (i) the scatter of radioactively stable $r$-process element abundances, (ii) the largest $r$-process enrichment values observed in any solar neighborhood stars and (iii) the isotope abundance ratios of different radioactive $r$-process elements ($^{244}$Pu/$^{238}$U and $^{247}$Cm/$^{238}$U) at the early solar system as compared to their formation ratios. Our results indicate that the Galactic $r$-process rate and the diffusion coefficient are respectively $r<4\times 10^{-5}\mbox{ yr}^{-1}, D>0.1 \mbox{ kpc}^2\mbox{Gyr}^{-1}$ ($r<4\times 10^{-6}\mbox{ yr}^{-1}, D>0.5 \mbox{ kpc}^2\mbox{Gyr}^{-1}$ for collapsars or similarly prolific $r$-process sources) with allowed values satisfying an approximate anti-correlation such that $D\approx r^{-2/3}$, implying that the time between two $r$-process events that enrich the same location in the Galaxy, is $\tau_{\rm mix}\approx 100-200\mbox{ Myr}$. This suggests that a fraction of $\sim 0.8$ ($\sim 0.5$) of the observed $^{247}$Cm ($^{244}$Pu) abundance is dominated by one $r$-process event in the early solar system. Radioactively stable element abundances are dominated by contributions from $\sim 10$ different events in the early solar system. For metal poor stars (with [Fe/H]$\lesssim -2$), their $r$-process abundances are dominated by either a single or several events, depending on the star formation history.

[10]  arXiv:2003.01131 [pdf, other]

Title: When Gas Dynamics Decouples from Galactic Rotation: Characterizing ISM Circulation in Disk Galaxies

Authors: Jose Utreras, Guillermo A. Blanc, Andres Escala, Sharon Meidt, Eric Emsellem, Frank Bigiel, Simon C. O. Glover, Jonathan Henshaw, Alex Hygate, J. M. Diederik Kruijssen, Erik Rosolowsky, Eva Schinnerer, Andreas Schruba

Comments: Accepted for publication in The Astrophysical Journal, 20 pages, 16 figures

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

In galactic disks, galactic rotation sets the bulk motion of gas, and its energy and momentum can be transferred towards small scales. Additionally, in the interstellar medium, random and non-circular motions arise from stellar feedback, cloud-cloud interactions, instabilities, among other processes. Our aim is to comprehend to which extent small scale gas dynamics is decoupled from galactic rotation. We study the relative contributions of galactic rotation and local non-circular motions to the circulation of gas, $\Gamma$, a macroscopic measure of local rotation, defined as line integral of velocity field around a closed path. We measure the circulation distribution as a function of spatial scale in a set of simulated disk galaxies and we model the velocity field as the sum of galactic rotation and a Gaussian random field. The random field is parametrized by a broken power law in Fourier space, with a break at the scale $\lambda_c$. We define the spatial scale $\lambda_{\rm eq}$ at which galactic rotation and non-circular motions contribute equally to $\Gamma$. For our simulated galaxies, the gas dynamics at the scale of molecular clouds is usually dominated by non-circular motions, but in the center of galactic disks galactic rotation is still relevant. Our model shows that the transfer of rotation from large scales breaks at the scale $\lambda_c$ and this transition is necessary to reproduce the circulation distribution. We find that $\lambda_{\rm equi}$, and therefore the structure of the gas velocity field, is set by the local conditions of gravitational stability, and stellar feedback.

[11]  arXiv:2003.01132 [pdf, other]

Title: The Strength of the Dynamical Spiral Perturbation in the Galactic Disk

Authors: Anna-Christina Eilers, David W. Hogg, Hans-Walter Rix, Jason A. S. Hunt, Jean-Baptiste Fouvry, Tobias Buck

Comments: submitted to ApJ

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

The mean Galactocentric radial velocities $\langle v_{R}\rangle(R,\phi)$ of luminous red giant stars within the mid-plane of the Milky Way reveal a spiral signature, which could plausibly reflect the response to a non-axisymmetric perturbation of the gravitational potential in the Galactic disk. We apply a simple steady-state toy model of a logarithmic spiral to interpret these observations, and find a good qualitative and quantitative match. Presuming that the amplitude of the gravitational potential perturbation is proportionate to that in the disk's surface mass density, we estimate the surface mass density amplitude to be $\Sigma_{\rm max} (R_{\odot})= 14\pm5\,\rm M_{\odot}\,pc^{-2}$ at the solar radius. Combined with the local disk density, this implies a surface mass density contrast between the arm and inter-arm regions of approximately $\pm 20\%$ at the solar radius, with an increase towards larger Galactocentric radii. Our model constrains the pitch angle of the {\it dynamical} spiral arms to be $12.7^{\circ}\pm1.2^{\circ}$.

[12]  arXiv:2003.01136 [pdf, other]

Title: A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780

Authors: Ryan Cloutier, Jason D. Eastman, Joseph E. Rodriguez, Nicola Astudillo-Defru, Xavier Bonfils, Annelies Mortier, Christopher A. Watson, Manu Stalport, Matteo Pinamonti, Florian Lienhard, Avet Harutyunyan, Mario Damasso, David W. Latham, Karen A. Collins, Robert Massey, Jonathan Irwin, Jennifer G. Winters, David Charbonneau, Carl Ziegler, Elisabeth Matthews, Ian J. M. Crossfield, Laura Kreidberg, Samuel N. Quinn, George Ricker, Roland Vanderspek, Sara Seager, Joshua Winn, Jon M. Jenkins, Michael Vezie, Stéphane Udry, Joseph D. Twicken, Peter Tenenbaum, Alessandro Sozzetti, Damien Ségransan, Joshua E. Schlieder, Dimitar Sasselov, Nuno C. Santos, Ken Rice, Benjamin V. Rackham, Ennio Poretti, Giampaolo Piotto, David Phillips, Francesco Pepe, Emilio Molinari, Lucile Mignon, Giuseppina Micela, et al. (41 additional authors not shown)

Comments: 8 figures, 6 tables, submitted to AAS journals. CSV file of the RV measurements (i.e. Table 2) are included in the source code

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

We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, $V=13.07$, $K_s=8.204$, $R_s$=0.374 R$_{\odot}$, $M_s$=0.401 M$_{\odot}$, d=22 pc). The two planet candidates are identified in a single TESS sector and are validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of $P_b=0.77$ days, $P_c=12.25$ days and sizes $r_{p,b}=1.33\pm 0.07$ R$_{\oplus}$, $r_{p,c}=2.30\pm 0.16$ R$_{\oplus}$, the two planets span the radius valley in period-radius space around low mass stars thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. By combining 55 precise radial-velocity measurements from HARPS and HARPS-N, we measure planet masses of $m_{p,b}=3.12\pm 0.51$ M$_{\oplus}$ and $m_{p,c}=8.5\pm 1.6$ M$_{\oplus}$ which indicates that LTT 3780b has a bulk composition consistent with being Earth-like, while LTT 3780c likely hosts an extended H/He envelope. We show that the recovered planetary masses are consistent with predictions from both photoevaporation and from core-powered mass loss models. The physical and orbital planet parameters, combined with the brightness and small size of LTT 3780, render both of the known LTT 3780 planets as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley.

[13]  arXiv:2003.01137 [pdf, ps, other]

Title: UV line driven disc wind as the origin of ultrafast outflows in AGN

Authors: Misaki Mizumoto, Mariko Nomura, Chris Done, Ken Ohsuga, Hirokazu Odaka

Comments: 14 pages, 16 figures, submitted to MNRAS

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

UltraFast Outflows (UFO) are observed in some active galactic nuclei (AGN), with blueshifted and highly ionised Fe-K absorption features. AGN typically have a UV bright accretion flow, so UV line driving is an obvious candidate for launching these winds, but this mechanism requires material with UV opacity, in apparent conflict with the observed high ionisation state of the wind. In this paper we synthesise the X-ray energy spectra resulting from different lines of sight through a state of the art radiation hydrodynamics UV line driven disc wind simulation. We demonstrate that there are some lines of sight which only intercept highly ionised and fast outflowing material. The cooler material required for the UV line driving acceleration is out of the line of sight, close to the disc, shielded from the X-rays by a failed wind. We fit these simulated wind spectra to data from the archetypal UFO source PG 1211+143 and show that they broadly reproduce the depth and velocity of the iron absorption lines seen. This directly demonstrates that UV line driving is a viable mechanism to launch UFOs. We simulate microcalorimeter observations of this wind and show that their high energy resolution can resolve the detailed structure in the wind and recover the wind energetics when combined with models which correctly estimate the wind launch radius. New data from microcalorimeters will pave the way for physical predictions of AGN wind feedback in cosmological simulations.

[14]  arXiv:2003.01140 [pdf, other]

Title: The CARMENES search for exoplanets around M dwarfs. Two planets on the opposite sides of the radius gap transiting the nearby M dwarf LP 729-54

Authors: G. Nowak, R. Luque, H. Parviainen, E. Pallé, K. Molaverdikhani, V. J. S. Béjar, J. Lillo-Box, C. Rodríguez-López, J. A. Caballero, M. Zechmeister, V. M. Passegger, C. Cifuentes, A. Schweitzer, N. Narita, B. Cale, N. Espinoza, F. Murgas, M. R. Zapatero Osorio, F. J. Pozuelos, F. J. Aceituno, P. J. Amado, K. Barkaoui, D. Barrado, F. F. Bauer, Z. Benkhaldoun, D. A. Caldwell, N. Casasayas Barris, P. Chaturvedi, G. Chen, K. A. Collins, K. I. Collins, M. Cortés-Contreras, I. J. M. Crossfield, J.P. de León, E. Díez Alonso, S. Dreizler, M. El Mufti, E. Esparza-Borges, Z. Essack, A. Fukui, M. Gillon, P. Guerra, A. Hatzes, T. Henning, E. Herrero, K. Hesse, T. Hirano, S. B. Howell, S. V. Jeffers, E. Jehin, J. M. Jenkins, A. Kaminski, J. Kemmer, J. F. Kielkopf, D. Kossakowski, et al. (39 additional authors not shown)

Comments: Comments: 21 pages, 15 figures, 4 tables, submitted to A&A

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

We present the discovery and characterisation of two transiting planets observed by the Transiting Exoplanet Survey Satellite (TESS) orbiting the nearby (d ~ 22 pc), bright (J ~ 9 mag) M3.5 dwarf LP 729-54 (TOI-732). We confirm both planets and their association with LP 729-54 via ground-based photometry and determine their masses using precise radial velocities measured with the CARMENES spectrograph. Precise stellar parameters determined from CARMENES high resolution spectra confirm that LP 729-54 is a mid-M dwarf with an effective temperature of T_eff = 3360 +\- 51 K, a surface gravity of log(g) = 4.81 +/- 0.04 (cgs), and an iron abundance of [Fe/H] = 0.09 +/- 0.16 dex, with an inferred mass of M_star = 0.379 +/- 0.016 M_sun and a radius of R_star = 0.382 +/- 0.012 R_sun. The ultra-short period planet LP 729-54 b (P_b = 0.77 d) with a radius of 1.35^{+0.06}_{-0.06} R_earth, a mass of 2.34^{+0.24}_{-0.23} M_earth, and a bulk density of 5.24^{+0.94}_{-0.81} g cm^{-3} joins the population of Earth-size planets with rocky, terrestrial composition. The outer planet, LP 729-54 c, with an orbital period of 12.25 d, radius of 2.42^{+0.10}_{-0.10} R_earth, mass of 6.29^{+0.63}_{-0.61} M_earth, and mean density of 2.45^{+0.44}_{-0.37} g cm^{-3} belongs to the population of dense sub-Neptunes. With the two planets located on opposite sides of the radius gap, this planetary system is an excellent target for testing planetary formation, evolution and atmospheric models. In particular, LP 729-54 c is an ideal object for atmospheric studies with the James Webb Space Telescope.

[15]  arXiv:2003.01141 [pdf, other]

Title: Resonant capture in quadruple stellar systems

Authors: Scott Tremaine

Comments: 13 pages, 1 figure, MNRAS in press

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

Some quadruple star systems in the hierarchical 2+2 configuration exhibit orbit-orbit resonances between the two compact binaries. We show that the most important resonances occur at period ratios of 1:1, 3:2 and 2:1. We describe the conditions required for capture and show that they can be satisfied at the 3:2 and 2:1 resonances in binaries that migrate significantly in semimajor axis after circularization, probably through magnetic braking or gravitational radiation.

[16]  arXiv:2003.01148 [pdf, other]

Title: A ringed pole-on outflow from DO Tauri revealed by ALMA

Authors: M. Fernández López (1), L. A. Zapata (2), L. F. Rodríguez (2), M. M. Vazzano (1), A. E. Guzmán (3), R. López (4) ((1) Instituto Argentino de Radioastronomía, Argentina, (2) Instituto de Radioastronomía y Astrofísica, México, (3) National Astronomical Observatory, Japan, (4) Departament d'Astronomia i Meteorologia, Spain)

Comments: 26 pages, 11 figures, accepted by ApJ

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

We present new ALMA Band 6 observations including the CO(2-1) line and 1.3 mm continuum emission from the surroundings of the young stellar object DO Tauri. The ALMA CO molecular data show three different series of rings at different radial velocities. These rings have radii around 220 au and 800 au. We make individual fits to the rings and note that their centers are aligned with DO Tauri and its optical high-velocity jet. In addition, we notice that the velocity of these structures increases with the separation from the young star. We discuss the data under the hypothesis that the rings represent velocity cuts through three outflowing shells that are possibly driven by a wide-angle wind, dragging the environment material along a direction close to the line of sight (i=19{\deg}). We estimate the dynamical ages, the mass, the momentum and the energy of each individual outflow shell and those of the whole outflow. The results are in agreement with those found in outflows from Class II sources. We make a rough estimate for the size of the jet/wind launching region, which needs to be of <15 au. We report the physical characteristics of DO Tauri's disk continuum emission (almost face-on and with a projected major axis in the north-south direction) and its velocity gradient orientation (north-south), indicative of disk rotation for a 1-2 Msun central star. Finally we show an HST [SII] image of the optical jet and report a measurement of its orientation in the plane of the sky.

[17]  arXiv:2003.01167 [pdf, other]

Title: Dust dynamics and vertical settling in gravitoturbulent protoplanetary discs

Authors: A. Riols, B. Roux, H. Latter, G. Lesur

Comments: Accepted in MNRAS, 13 pages

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

Gravitational instability (GI) controls the dynamics of young massive protoplanetary discs. Apart from facilitating gas accretion on to the central protostar, it must also impact on the process of planet formation: directly through fragmentation, and indirectly through the turbulent concentration of small solids. To understand the latter process, it is essential to determine the dust dynamics in such a turbulent flow. For that purpose, we conduct a series of 3D shearing box simulations of coupled gas and dust, including the gas's self-gravity and scanning a range of Stokes numbers, from 0.001 to ~0.2. First, we show that the vertical settling of dust in the midplane is significantly impeded by gravitoturbulence, with the dust scale-height roughly 0.6 times the gas scale height for centimetre grains. This is a result of the strong vertical diffusion issuing from (a) small-scale inertial-wave turbulence feeding off the GI spiral waves and (b) the larger-scale vertical circulations that naturally accompany the spirals. Second, we show that at R=50 AU concentration events involving sub-metre particles and yielding order 1 dust to gas ratios are rare and last for less than an orbit. Moreover, dust concentration is less efficient in 3D than in 2D simulations. We conclude that GI is not especially prone to the turbulent accumulation of dust grains. Finally, the large dust scale-height measured in simulations could be, in the future, compared with that of edge-on discs seen by ALMA, thus aiding detection and characterisation of GI in real systems.

[18]  arXiv:2003.01179 [pdf, other]

Title: Spatially resolved velocity structure in jets of DF Tau and UY Aur A

Authors: Anastasiia V Uvarova, Hans Moritz Günther, David A. Principe, P. Christian Schneider

Comments: 9 pages, 3 figures, submitted to AJ

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

Young stars accrete mass and angular momentum from their circumstellar disks. Some of them also drive outflows, which can be distinguished in optical forbidden emission lines (FELs). We analyze a sample of binary T Tauri stars observed with long-slit spectroscopy by the Hubble Space Telescope (HST), searching for spatially resolved outflows. We detect resolved [O I] emission in two cases out of twenty one. In DF Tau we resolve high and medium velocity outflows in a jet and counterjet out to 60 au. The outflows are accelerated within the inner 12 au and retain a constant speed thereafter. In UY Aur, we detect a blue- and a red-shifted outflow from UY Aur A, as well as a blue-shifted jet from UY Aur B. All of these features have been seen in [Fe II] with data taken ten years apart indicating that the underlying outflow pattern is stable on these timescales.

[19]  arXiv:2003.01187 [pdf, other]

Title: MEGA: Merger graphs of structure formation

Authors: William J. Roper, Peter A. Thomas, Chaichalit Srisawat

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

When following the growth of structure in the Universe, we propose replacing merger trees with merger graphs, in which haloes can both merge and split into separate pieces. We show that this leads to smoother mass growth and eliminates catastrophic failures in which massive haloes have no progenitors or descendants. For those who prefer to stick with merger trees, we find that trees derived from our merger graphs have similar mass growth properties to previous methods, but again without catastrophic failures. For future galaxy formation modelling, two different density thresholds can be used to distinguish host haloes (extended galactic haloes, groups and clusters) from higher-density subhaloes: sites of galaxy formation.

[20]  arXiv:2003.01222 [pdf, other]

Title: The Koala: A Fast Blue Optical Transient with Luminous Radio Emission from a Starburst Dwarf Galaxy at $z=0.27$

Authors: Anna Y. Q. Ho (1), D. A. Perley (2) S. R. Kulkarni (1), I. Andreoni (1), E. C. Bellm (3), K. B. Burdge (1), P. Chandra (4), M. Coughlin, K. De (1), D. Z. J. Dong (1), V. Z. Golkhou (3,6,7), M. J. Graham (1), D. D. Fredericks (8), G. Helou (9), A. Horesh (10), R. R. Laher (9), F. Masci (9), A. Ridnaia (8), B. Rusholme (9), D. L. Shupe (9), D. S. Svinkin (8) ((1) Caltech, (2) LJMU, (3) DIRAC Institute, UW, (4) NCRA, (5) U. Minnesota, (6) eScience Institute, (7) Moore-Sloan, WRF Innovation, DIRAC Fellow, (8) Ioffe Institute, (9) IPAC, (10) Racah Institute)

Comments: 21 pages, 10 figures. Submitted to ApJ on 2 March 2020. Comments welcome!

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

We present ZTF18abvkwla (the "Koala"), a fast blue optical transient discovered in the Zwicky Transient Facility (ZTF) One-Day Cadence (1DC) Survey. This event has a number of features in common with the groundbreaking transient AT2018cow: blue colors at peak ($g-r\approx-0.5$), a short rise time from half-max of under two days, a decay time of only three days, a high optical luminosity ($M_{g,\mathrm{peak}}\approx-20.8$), a hot ($\gtrsim 40,000\,$K) featureless spectrum at peak light, and a luminous radio counterpart ($\nu L_\nu \gtrsim 10^{40}\,$erg sec$^{-1}$ at 10 GHz). The radio luminosity of ZTF18abvkwla exceeds that of AT2018cow by an order of magnitude, and the late-time ($\Delta t\gtrsim80\,$days) light curve resembles that of long-duration gamma-ray bursts (GRBs). The host galaxy is a dwarf starburst galaxy ($M\approx5\times10^{8}\,M_\odot$, $\mathrm{SFR}\approx7\,M_\odot\,$year$^{-1}$) that is moderately metal-enriched ($\log\mathrm{[O/H]} \approx 8.5$), similar to the hosts of GRBs and superluminous supernovae. As in AT2018cow, the radio and optical emission in ZTF18abvkwla likely arise from two separate components: the radio from fast-moving collimated ejecta and the optical from shock-interaction with confined dense material ($<0.07\,M_\odot$ in $\sim 10^{15}\,$cm). Compiling transients in the literature with $t_\mathrm{rise} <5\,$days and $M_\mathrm{peak}<-20$, we find that a significant number are engine-powered,and suggest that the high peak optical luminosity is directly related to the presence of this engine. From 18 months of the 1DC survey, we find that transients in this rise-luminosity phase space are at least two orders of magnitude less common than CC SNe. Finally, we discuss strategies for identifying such events with future facilities like the Large Synoptic Survey Telescope, and prospects for detecting accompanying X-ray and radio emission.

[21]  arXiv:2003.01224 [pdf]

Title: Photometry of Kuiper Belt Object (486958) Arrokoth from New Horizons LORRI

Authors: Jason D. Hofgartner, Bonnie J. Buratti, Susan D. Benecchi, Ross A. Beyer, Andrew Cheng, James T. Keane, Tod R. Lauer, Catherine B. Olkin, Joel W. Parker, Kelsi N. Singer, John R. Spencer, S. Alan Stern, Anne J. Verbiscer, Harold A. Weaver, New Horizons Geology, Geophysics Team, New Horizons LORRI Team

Comments: In press in Icarus

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

On January 1st 2019, the New Horizons spacecraft flew by the classical Kuiper belt object (486958) Arrokoth (provisionally designated 2014 MU69), possibly the most primitive object ever explored by a spacecraft. The I/F of Arrokoth is analyzed and fit with a photometric function that is a linear combination of the Lommel-Seeliger (lunar) and Lambert photometric functions. Arrokoth has a geometric albedo of p_V = 0.21_(-0.04)^(+0.05) at a wavelength of 550 nm and ~0.24 at 610 nm. Arrokoth's geometric albedo is greater than the median but consistent with a distribution of cold classical Kuiper belt objects whose geometric albedos were determined by fitting a thermal model to radiometric observations. Thus, Arrokoth's geometric albedo adds to the orbital and spectral evidence that it is a cold classical Kuiper belt object. Maps of the normal reflectance and hemispherical albedo of Arrokoth are presented. The normal reflectance of Arrokoth's surface varies with location, ranging from ~0.10-0.40 at 610 nm with an approximately Gaussian distribution. Both Arrokoth's extrema dark and extrema bright surfaces are correlated to topographic depressions. Arrokoth has a bilobate shape and the two lobes have similar normal reflectance distributions: both are approximately Gaussian, peak at ~0.25 at 610 nm, and range from ~0.10-0.40, which is consistent with co-formation and co-evolution of the two lobes. The hemispherical albedo of Arrokoth varies substantially with both incidence angle and location, the average hemispherical albedo at 610 nm is 0.063 +/- 0.015. The Bond albedo of Arrokoth at 610 nm is 0.062 +/- 0.015.

[22]  arXiv:2003.01230 [pdf, other]

Title: Laboratory investigations of Lunar ice imaging in permanently shadowed regions using reflected starlight

Authors: Paul J. Godin, Jacob L. Kloos, Alex Seguin, John E. Moores

Comments: Submitted to Acta Astronautica

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

A proof of concept for a frost detection imager using reflected starlight is presented; the limitations of this technique are explored experimentally. An ice-covered lunar surface is simulated inside a vacuum chamber, which is then illuminated with a lamp containing UV and visible output to simulate the wavelengths of the background starfield. The simulated lunar surface is imaged with a camera utilizing a UV and visible filter pairing. At Lyman-alpha wavelengths, ice has low reflectivity, and on average appears darker than the regolith in the UV image. In visible wavelengths, this behaviour is reversed, with ice appearing brighter than regolith. UV/VIS image ratioing is subsequently performed in order to discern frost from the lunar regolith simulant in order to demonstrate the capability of this technology for locating the presence of ice on the lunar surface. When the two images are ratioed, the signal to noise ratio to distinguish ice from regolith improves by 36%. In cases where the presence of shadows and specular reflection make distinguishing ice from regolith in either a single UV or visible image difficult, ratioing the images makes the distinction clear.

[23]  arXiv:2003.01241 [pdf, other]

Title: Deep modeling of quasar variability

Authors: Yutaro Tachibana, Matthew J. Graham, Nobuyuki Kawai, S. G. Djorgovski, Andrew J. Drake, Ashish A. Mahabal, Daniel Stern

Comments: 22 pages, 20 figures, submitted to ApJ

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

Quasars have long been known as intrinsically variable sources, but the physical mechanism underlying the temporal optical/UV variability is still not well understood. We propose a novel nonparametric method for modeling and forecasting the optical variability of quasars utilizing an autoencoder neural network to gain insight into the underlying processes. The autoencoder is trained with ~15,000 decade-long quasar light curves obtained by the Catalina Real-time Transient Survey selected with negligible flux contamination from the host galaxy. The autoencoder's performance in forecasting the temporal flux variation of quasars is superior to that of the damped random walk process. We find a temporal asymmetry in the optical variability and a novel relation - the amplitude of the variability asymmetry decreases as luminosity and/or black hole mass increases - is suggested with the help of autoencoded features. The characteristics of the variability asymmetry are in agreement with those from the self-organized disk instability model, which predicts that the magnitude of the variability asymmetry decreases as the ratio of the diffusion mass to inflow mass in the accretion disk increases.

[24]  arXiv:2003.01259 [pdf, ps, other]

Title: Discontinuity gravity modes in hybrid stars: assessing the role of rapid and slow phase conversions

Authors: L. Tonetto, G. Lugones

Comments: 12 pages, 6 figures

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

Discontinuity gravity modes may arise in perturbed quark-hadron hybrid stars when a sharp density jump exists in the stellar interior and are a potential fingerprint to infer the existence of quark matter cores in compact objects. When a hybrid star is perturbed, conversion reactions may occur at the quark-hadron interface and may have a key role in global stellar properties such as the dynamic stability and the quasi-normal mode spectrum. In this work we study the role of the conversion rate at the interface. To this end, we first derive the junction conditions that hold at the sharp interface of a non-radially perturbed hybrid star in the case of slow and rapid conversions. Then, we analyse the discontinuity $g$-mode in both cases. For rapid conversions, the discontinuity $g$-mode has zero frequency because a displaced fluid element near the phase splitting surface adjusts almost immediately its composition to its surroundings and gravity cannot provide a buoyancy force. For slow conversions, a $g$-mode exists and its properties are analysed here using modern hadronic and quark equations of state. Moreover, it has been shown recently that in the case of slow conversions an extended branch of stable hybrid configurations arises for which $\partial M/ \partial \epsilon_c <0$. We show that $g$-modes of the standard branch (that is, the one with $\partial M/ \partial \epsilon_c > 0$) have frequencies and damping times in agreement with previous results in the literature. However, $g$-modes of the extended branch have significantly larger frequencies (in the range $1-2 \, \mathrm{kHz}$) and much shorter damping times (few seconds in some cases). We discuss the detectability of $g$-mode GWs with present and planned GW observatories.

[25]  arXiv:2003.01339 [pdf, ps, other]

Title: Gamma-ray Emission Properties of Four Bright Fermi-LAT AGNs: Implications on Emission Processes

Authors: Pankaj Kushwaha (IAG-USP), Atreyee Sinha (IUCAA), Ranjeev Misra (IUCAA), K. P. Singh (TIFR), E. M. de Gouveia Dal Pino (IAG-USP)

Comments: 4 Pages, 4 Figures, Proceeding of Brazillian Astronomical Society (Annual Meeting)

Journal-ref: BSAB (2018) 30, 222-225

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

The X-ray, Ultraviolet, Optical emission from radio-quiet AGNs, black hole binaries, and other compact sources, in general, follow a lognormal flux distribution, a linear rms-flux relation, and a (broken) power-law power spectral densities (PSDs). These characteristics are normally attributed to the multiplicative combination of fluctuations in the accretion disk. Similar features have been inferred for some well-observed blazars in different energy bands, but a systematic study over a long duration is still missing. Using a continuous gamma-ray light curves over 3-days cadence from August 2008 - October 2015, we present the first systematic study of these features in four sources: the FR I radio galaxy NGC 1275 and three blazars- Mrk 421, B2 1520+31 and PKS 1510-089. For all, except Mrk 421, the flux spans $\gtrsim$ 2 orders of magnitude. For blazars, a log-normal profile describes the flux histograms better compared to a Gaussian, while none is favored for NGC 1275, the only non-blazar source, suggesting a complex distribution. Regardless of flux histogram profile, the rms-flux relation is linear for all with PSDs being consistent with a power-law shot noise spectrum despite hints of breaks. The inferred results are consistent with the properties of unresolved magnetic reconnection sites, as inferred in the X-ray emission from the whole Solar disk and the statistical characteristics of magnetic reconnection based minijets-in-a-jet model. The results, thus, suggest a strong jet-accretion-disk coupling with energy input from the central source being distributed over a wide range in time and energy by the reconnection process depending on the geometry and local physical conditions.

[26]  arXiv:2003.01374 [pdf]

Title: Irradiance Variations due to Orbital and Solar Inertial Motion: The Effect on Earth's Surface Temperature

Authors: Gerald E. Marsh

Comments: 15 pages, 13 Figures

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

Variation in total solar irradiance is thought to have little effect on the Earth's surface temperature because of the thermal time constant--the characteristic response time of the Earth's global surface temperature to changes in forcing. This time constant is large enough to smooth annual variations but not necessarily variations having a longer period such as those due to solar inertial motion; the magnitude of these surface temperature variations is estimated.

[27]  arXiv:2003.01377 [pdf, ps, other]

Title: New Expansion Rate Estimate of the Scorpius-Centaurus Association Based on T Tauri Stars from the Gaia DR2 Catalog

Authors: V.V. Bobylev, A.T. Bajkova

Comments: 14 pages, 2 figures, 2 tables

Journal-ref: Astronomy Reports, 2020, Vol. 64, No 4, pp. 326--335

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

The kinematic properties of the Scorpius-Centaurus association were studied using spatial velocities of approximately 700 young T Tauri stars. Their proper motions and trigonometric parallaxes were selected by Zari et al. from the Gaia DR2 catalog, and radial velocities were taken from various sources. The linear expansion coefficients new estimate of the association $K=39\pm2$ km/s/kpc is obtained by considering the influence of the galactic spiral density wave with an amplitude of radial disturbances $f_R=5$ km/s and solar phase in the wave $-120^\circ$. The proper rotation of the association is shown to be small. The residual velocity ellipsoid of these stars has semimajor axes $\sigma_{1,2,3}=(7.72,1.87,1.74)\pm(0.56,0.37,0.22)$ km/s and is positioned at an angle $12\pm2^\circ$ to the galactic plane.

[28]  arXiv:2003.01382 [pdf, other]

Title: Compact Bright Radio-loud AGNs -- III. A Large VLBA Survey at 43 GHz

Authors: X.-P. Cheng, T. An, S. Frey, X.-Y. Hong, X. He, K. I. Kellermann, M. L. Lister, B.-Q. Lao, X.-F. Li, P. Mohan, J. Yang, X.-C. Wu, Z.-L. Zhang, Y.-K. Zhang, W. Zhao

Comments: Accepted for publication in ApJS

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

We present the observational results from the 43-GHz Very Long Baseline Array (VLBA) observations of 124 compact radio-loud active galactic nuclei (AGNs) that were conducted between 2014 November and 2016 May. The typical dimensions of the restoring beam in each image are about 0.5 mas $\times$ 0.2 mas. The highest resolution of 0.2 mas corresponds to a physical size of 0.02 pc for the lowest redshift source in the sample. The 43-GHz very long baseline interferometry (VLBI) images of 97 AGNs are presented for the first time. We study the source compactness on milli-arcsec (mas) and sub-mas scales, and suggest that 95 sources in our sample are suitable for future space VLBI observations. By analyzing our data supplemented with other VLBA AGN surveys from literature, we find that the core brightness temperature increases with increasing frequency below a break frequency ~ 7 GHz, and decreases between ~7--240~GHz but increases again above~240 GHz in the rest frame of the sources. This indicates that the synchrotron opacity changes from optically thick to thin. We also find a strong statistical correlation between radio and $\gamma$-ray flux densities. Our correlation is tighter than those in literature derived from lower-frequency VLBI data, suggesting that the $\gamma$-ray emission is produced more co-spatially with the 43-GHz VLBA core emission. This correlation can also be extrapolated to the un-beamed AGN population, implying that a universal $\gamma$-ray production mechanism might be at work for all types of AGNs.

[29]  arXiv:2003.01397 [pdf, ps, other]

Title: Unveiling the monster heart: unbeamed properties of blazar 4C 71.07

Authors: C. M. Raiteri (1), J. A. Acosta Pulido (2 and 3), M. Villata (1), M. I. Carnerero (1), P. Romano (4), S. Vercellone (4) ((1) INAF, Osservatorio Astrofisico di Torino, Italy, (2) Instituto de Astrofisica de Canarias (IAC), Spain, (3) Departamento de Astrofisica, Universidad de La Laguna, Spain, (4) INAF, Osservatorio Astronomico di Brera, Italy)

Comments: 13 pages, 13 figures, in press for MNRAS

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

4C 71.07 is a high-redshift blazar whose optical radiation is dominated by quasar-like nuclear emission. We here present the results of a spectroscopic monitoring of the source to study its unbeamed properties. We obtained 24 optical spectra at the Nordic Optical Telescope (NOT) and William Herschel Telescope (WHT) and 3 near-infrared spectra at the Telescopio Nazionale Galileo (TNG). They show no evidence of narrow emission lines. The estimate of the systemic redshift from the H$\beta$ and H$\alpha$ broad emission lines leads to $z_{\rm sys}=2.2130 \pm 0.0004$. Notwithstanding the nearly face-on orientation of the accretion disc, the high-ionization emission lines present large broadening as well as noticeable blueshifts, which increase with the ionizing energy of the corresponding species. This is a clear indication of strong ionized outflows. Line broadening and blueshift appear correlated. We applied scaling relationships to estimate the mass of the supermassive black hole from the Balmer and C IV lines, taking into account the prescriptions to correct for outflow. They give $M_{\rm BH} \sim 2 \times 10^9 \, M_\odot$. We derived an Eddington luminosity $L_{\rm Edd} \sim 2.5 \times 10^{47} \rm \, erg \, s^{-1}$ $\sim L_{\rm disc}$, and a broad line region luminosity $L_{\rm BLR} \sim 1.5 \times 10^{46} \rm \, erg \, s^{-1}$. The line fluxes do not show significant variability in time. In particular, there is no line reaction to the jet flaring activity detected in 2015 October and November. This implies that the jet gives no contribution to the photoionization of the broad line region in the considered period.

[30]  arXiv:2003.01424 [pdf, other]

Title: Paradigms and Scenarios for the Dark Matter Phenomenon

Authors: Paolo Salucci, Nicola Turini

Comments: Invited talk at the 19th Lomonosov Conference on Elementary Particle Physics (Moscow, 22-28/8, 2019). In printing on "Particle Physics at the Year of 150th Anniversary of the Mendeleev's PeriodicTable of the Chemical Elements" ,Ed: A. Studenikin (World Scienti?c,Singapore). 10 pages 5 Figures Comments wellcome

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

Well known scaling laws among the structural properties of the dark and the luminous matter in disc systems are too complex to be arisen by two inert components that just share the same gravitational field. This brings us to critically focus on the 30 year old paradigm, that, resting on a priori knowledge of the nature of dark matter (DM), has led us to a restricted number of scenarios, especially favouring the collisionless $\Lambda$Cold Dark Matter one.
Motivated by such observational evidence, we propose to resolve the dark matter mystery by following a new paradigm: the nature of DM must be guessed/derived by deeply analyzing the properties of the dark and luminous mass distribution at galactic scales. The immediate application of this paradigm leads us to the existence of a direct interaction between dark and Standard Model particles which has finely shaped the inner regions of galaxies.

[31]  arXiv:2003.01444 [pdf, other]

Title: A new insight on stellar age I. Theoretical trends with gyro-age and rotation

Authors: D. B. de Freitas

Comments: 5 pages and 1 figure. (Brainstorm)

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

In this first work attempts to analytically explain the effects on the magnetic braking index, $q$, caused by the evolution of stellar velocity in main-sequence stars, and estimated by de Freitas \& De Medeiros (2013). We have found that the effect of $q$ is here a determining factor for understanding the delicate mechanisms that control the spin-down of stars as a function of the mass of stars. We note that our models predict that the calculated ages are distinct from gyrochronology ages. Indeed, the gyro-ages are measured considering only the canonical value of the Skumanich relation ($q$=3). As a result, we find that the age of stars can be well-determined when $q$ is free parameter. We also verified that for rotation periods less than $\sim$ 5 days (i.e., fast rotators) there is a strong discrepancy among the different indexes $q$. In addition, the ages measured by gyrochronology model can be underestimated according to mass range selected. In conclusion, we suggest that the generalized gyro-ages by magnetic braking index can be an interesting way to better understand the idea of rotation as a clock.

[32]  arXiv:2003.01448 [pdf, other]

Title: Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548

Authors: Keith Horne, G. De Rosa, B. M. Peterson, A. J. Barth, J. Ely, M. M. Fausnaugh, G. A. Kriss, L. Pei, S. M. Adams, M. D. Anderson, P. Arevalo, T G. Beatty, V. N. Bennert, M. C. Bentz, A. Bigley, S. Bisogni, G. A. Borman, T. A. Boroson, M. C. Bottorff, W. N. Brandt, A. A. Breeveld, M. Brotherton, J. E. Brown, J. S. Brown, E. M. Cackett, G. Canalizo, M. T. Carini, K. I. Clubb, J. M. Comerford, E. M. Corsini, D. M. Crenshaw, S. Croft, K. V. Croxall, E. Dalla Bonta, A. J. Deason, M. Dehghanian, A. De Lorenzo-Caceres, K. D. Denney, M. Dietrich, C. Done, R. Edelson, N. V. Efimova, M. Eracleous, P. A. Evans, G. J. Ferland, A. V. Filippenko, K. Flatland, O. D. Fox, E. Gardner, E. L. Gates, N. Gehrels, S. Geier, J. M. Gelbord, M. R. Goad, L. Gonzalez, V. Gorjian, J. E. Greene, C. J. Grier, D. Grupe, et al. (99 additional authors not shown)

Comments: 19 pages, 9 figures, to be submitted to ApJ

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

We report velocity-delay maps for prominent broad emission lines, Ly_alpha, CIV, HeII and H_beta, in the spectrum of NGC5548. The emission-line responses inhabit the interior of a virial envelope. The velocity-delay maps reveal stratified ionization structure. The HeII response inside 5-10 light-days has a broad single-peaked velocity profile. The Ly_alpha, CIV, and H_beta responses peak inside 10 light-days, extend outside 20 light-days, and exhibit a velocity profile with two peaks separated by 5000 km/s in the 10 to 20 light-day delay range. The velocity-delay maps show that the M-shaped lag vs velocity structure found in previous cross-correlation analysis is the signature of a Keplerian disk with a well-defined outer edge at R=20 light-days. The outer wings of the M arise from the virial envelope, and the U-shaped interior of the M is the lower half of an ellipse in the velocity-delay plane. The far-side response is weaker than that from the near side, so that we see clearly the lower half, but only faintly the upper half, of the velocity--delay ellipse. The delay tau=(R/c)(1-sin(i))=5 light-days at line center is from the near edge of the inclined ring, giving the inclination i=45 deg. A black hole mass of M=7x10^7 Msun is consistent with the velocity-delay structure. A barber-pole pattern with stripes moving from red to blue across the CIV and possibly Ly_alpha line profiles suggests the presence of azimuthal structure rotating around the far side of the broad-line region and may be the signature of precession or orbital motion of structures in the inner disk. Further HST observations of NGC 5548 over a multi-year timespan but with a cadence of perhaps 10 days rather than 1 day could help to clarify the nature of this new AGN phenomenon.

[33]  arXiv:2003.01454 [pdf, other]

Title: Are observed H i filaments turbulent fraud or density structures? Velocity caustics, facts and fakes

Authors: P. M. W. Kalberla, U. Haud

Comments: Submitted to A&A, first revision

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

Context. The interstellar medium is affected by turbulence and observed H i structures in channel maps are shaped by turbulent motions. It is taken for granted by a few theoreticians that observed H i structures do not represent real density enhancement but velocity caustics, caused by velocity crowding. This interpretation was questioned and objections by Clark et al. led to violent debates. Aims. To settle the discussion we verify theoretical key parameters by using Effelsberg Bonn H i Survey (EBHIS) observations. Methods. We apply unsharp masking to determine filamentary H i structures at high spatial frequencies. In addition we use Gaussian parameters to distinguish the cold neutral medium (CNM) from observed H i column densities. We compare power spectra and spatial distributions of dust and H i column densities, distinguishing CNM and multiphase column densities at various velocity widths. Results. Observations contradict the Velocity Channel Analysis (VCA) postulate that the spectral index should steepen with the width of the velocity window. We rather find that the thin slice spectral index depends strongly on the H i phase composition. Multiphase power spectra are steeper for regions with cold gas. VCA denies such H i phase dependencies on the power distribution. Separating the CNM we find that the power spectra are significantly flatter than those for the multiphase H i composite. We observe excess CNM power for small scale structures originating from cold dust bearing filaments that are embedded in the CNM. Spectral indices for narrow channel widths depend on the Doppler temperature of the H i gas. In presence of enhanced small scale H i structure the far infrared emission from dust is also enhanced. Conclusions. Small scale cold filamentary H i structures are predominantly caused by density enhancements due to phase transitions rather than by velocity caustics.

[34]  arXiv:2003.01457 [pdf, other]

Title: Follow-up imaging observations of comet 2I/Borisov

Authors: M. Mugrauer, R. Bischoff, W. Stenglein, J. Trautmann, B. Baghdasaryan, S. Schlagenhauf

Comments: 14 pages, 4 figures, 8 tables, accepted for publication in AN

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

Follow-up imaging observations of the first detected interstellar comet 2I/Borisov are presented, which were carried out with the Schmidt-Teleskop-Kamera at the University Observatory Jena in 11 observing epochs in October and November 2019. The orbital solution of the comet, derived from the obtained astrometric measurements, confirms its highly eccentric ($e=3.3570 \pm 0.0006$) and inclined ($i=44.0524 \pm 0.0004\,^\circ$) orbit, that proves the interstellar origin of the comet. According to our best-fitting orbital solution, comet 2I/Borisov reaches its perihelion on 2019 Dec 8 ($q=2.0066$ au) and its closest encounter with Earth on 2019 Dec 28 ($\Delta_{\text{min}}=1.9368$ au). The distance corrected brightness of the nucleus of the comet clearly exhibits a linear correlation with its phase angle. The slope of this correlation indicates the activity of the comet, which is also detected in deep imaging data, taken in 5 observing epochs, showing the coma and the tail of the comet. During our observing campaign the coma of comet 2I/Borisov exhibits on average a diameter of $(4.57\pm0.38) \cdot 10^4$ km, and the length of the tail of the comet measures $(1.52\pm0.12) \cdot 10^5$ km, assuming an anti-solar orientation.

[35]  arXiv:2003.01476 [pdf, other]

Title: NGC 3894: a young radio galaxy seen by Fermi-LAT

Authors: G. Principe (1), G. Migliori (1,2), T. J. Johnson (3), F. D'Ammando (1), M. Giroletti (1), M. Orienti (1), C. Stanghellini (1), G. B. Taylor, (4) E. Torresi (5), C. C. Cheung (6) (1: INAF-IRA, 2: DiFA-BO, 3: GMU, 4: UNM, 5: INAF-OAS, 6: NRL)

Comments: Accepted by A&A on February 28, 2020. 8 pages, 7 figures

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

Context. According to radiative models, radio galaxies may produce gamma-ray emission from the first stages of their evolution. However, very few such galaxies have been detected by the Fermi Large Area Telescope (LAT) so far.
Aims. NGC 3894 is a nearby (z = 0.0108) object that belongs to the class of compact symmetric objects (CSOs, i.e., the most compact and youngest radio galaxies), which is associated with a gamma-ray counterpart in the Fourth Fermi-LAT source catalog. Here we present a study of the source in the gamma-ray and radio bands aimed at investigating its high-energy emission and assess its young nature.
Methods. We analyzed 10.8 years of Fermi-LAT data between 100 MeV and 300 GeV and determined the spectral and variability characteristics of the source. Multi-epoch very long baseline array (VLBA) observations between 5 and 15 GHz over a period of 35 years were used to study the radio morphology of NGC 3894 and its evolution.
Results. NGC 3894 is detected in gamma-rays with a significance >9 sigma over the full period, and no significant variability has been observed in the gamma-ray flux on a yearly time-scale. The spectrum is modeled with a flat power law ($\Gamma$ = 2.0$\pm$0.1) and a flux on the order of 2.2 $\times$ 10$^{-9}$ ph cm$^{-2}$ s$^{-1}$. For the first time, the VLBA data allow us to constrain with high precision the apparent velocity of the jet and counter-jet side to be $\beta_{\mathrm{app,NW}}$ = 0.132$\pm$0.004 and $\beta_{\mathrm{app,SE}}$ = 0.065$\pm$0.003, respectively.
Conclusions. Fermi-LAT and VLBA results favor the youth scenario for the inner structure of this object, with an estimated dynamical age of 59$\pm$5 years. The estimated range of viewing angle (10{\deg} < $\theta$ < 21{\deg}) does not exclude a possible jet-like origin of the gamma-ray emission.

[36]  arXiv:2003.01486 [pdf, other]

Title: Disentangling Atmospheric Compositions of K2-18 b with Next Generation Facilities

Authors: Quentin Changeat, Billy Edwards, Ahmed F. Al-Refaie, Angelos Tsiaras, Ingo P. Waldmann, Giovanna Tinetti

Comments: 12 pages, 12 figures

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

Recent analysis of the planet K2-18b has shown the presence of water vapour in its atmosphere. While the H2O detection is significant, the Hubble Space Telescope (HST) WFC3 spectrum suggests three possible solutions of very different nature which can equally match the data. These solutions include a primary cloudy atmosphere with traces of water vapour and a secondary atmosphere with a substantial amount of H2O and/or an undetectable gas such as N2. Additionally, the atmospheric pressure and the possible presence of a liquid/solid surface cannot be investigated with currently available observations. In this paper we used the best fit parameters from Tsiaras et al. (2019) to build JWST and Ariel simulations of the three scenarios. We have investigated 18 retrieval cases, which encompass the three scenarios and different observational strategies with the two observatories. Retrieval results show that twenty combined transits should be enough for the Ariel mission to disentangle the three scenarios, while JWST would require only two transits if combining NIRISS and NIRSpec data. This makes K2-18b an ideal target for atmospheric follow-ups by both facilities and highlights the capabilities of the next generation of space-based infrared observatories to provide a complete picture of low gravity planets.

[37]  arXiv:2003.01508 [pdf]

Title: Planetary Felsic Crust Formation at Shallow Depth

Authors: Anastassia Y. Borisova, Nail R. Zagrtdenov, Michael J. Toplis, Wendy A. Bohrson, Anne Nedelec, Oleg G. Safonov, Gleb S. Pokrovski, Georges Ceuleneer, Ilya N. Bindeman, Oleg E. Melnik, Klaus Peter Jochum, Brigitte Stoll, Ulrike Weis, Andrew Y. Bychkov, Andrey A. Gurenko, Svyatoslav Shcheka, Artem Terehin, Vladimir M. Polukeev, Dmitry A. Varlamov, Kouassi E.A. Chariteiro, Sophie Gouy, Philippe De Parseval

Comments: 62 pages, 9 figures, submitted to Frontiers in Earth Science

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Materials Science (cond-mat.mtrl-sci); Geophysics (physics.geo-ph)

Current theories suggest that on Earth and, possibly, on other terrestrial planets early in their history, the first continental crust may has been produced by direct melting of hydrated peridotite. However, the conditions, mechanisms and necessary ingredients of such production remain elusive. To fill this gap, we have conducted experiments of serpentinite melting in the presence of variable proportions of basaltic melt, at typical conditions of the shallow lithosphere and asthenosphere. These experiments revealed formation of silica-rich liquids, which are similar to tonalite-trondhjemite-granodiorite magmas (TTG) identified in modern terrestrial oceanic mantle settings. Our results suggest a new mechanism of aqueous fluid-assisted partial melting of peridotite that may have operated on the early Earth and Mars just after the solidification of an ultramafic-mafic magma ocean, leading to the formation of the first embryos of continental crust. The proposed mechanism of the continental crust formation may have been predominant before the onset of plate tectonics.

[38]  arXiv:2003.01511 [pdf, ps, other]

Title: Photometric Redshifts for the Hyper Suprime-Cam Subaru Strategic Program Data Release 2

Authors: Atsushi J. Nishizawa, Bau-Ching Hsieh, Masayuki Tanaka, Tadafumi Takata

Comments: 12 pages, 7 figures, 4 tables. arXiv admin note: text overlap with arXiv:1704.05988

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

We present a description of the second data release for the photometric redshift (photo-$z$) of the Subaru Strategic Program for the Hyper-Suprime Cam survey. Our photo-$z$ products for the entire area in the Data Release 2 are publicly available, and both our point estimate catalog products and full PDFs can be retrieved from the data release site, \url{https://hsc-release.mtk.nao.ac.jp/}.

[39]  arXiv:2003.01592 [pdf, ps, other]

Title: The Gamow Explorer: A Gamma-Ray Burst Mission to Study the High Redshift Universe

Authors: Nicholas E. White

Comments: 3 Pages, 1 table, Proceedings Yamada Conference LXXI: Gamma-ray Bursts in the Gravitational Wave Era 2019

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

Long Gamma Ray Bursts (LGRBs) can be used to address key questions on the formation of the modern universe including: How does the star formation rate evolve at high redshift? When and how did the intergalactic medium become re-ionized? What processes governed its early chemical enrichment? A LGRB signals when a massive star collapses to form a black hole and in doing so provides an independent tracer of the star formation rate. The LGRB afterglow is a bright back-light to view the host galaxy and intergalactic medium in absorption. The Gamow Explorer will be optimized to search for high redshift LGRBs, with a z>6 detection rate at least ten times the Neil Gehrels Swift Observatory. Furthermore it will go beyond Swift by using the photo-z technique to autonomously identify >80% of z>6 redshift LGRBs to enable rapid follow up by large ground based telescopes and JWST for spectroscopy and host galaxy identification. The Gamow Explorer will be proposed to the 2021 NASA MIDEX opportunity for launch in 2028.

[40]  arXiv:2003.01598 [pdf, ps, other]

Title: Non-LTE line formation for Si I-II-III in A-B stars and the origin of Si II emission lines in iota Her

Authors: Lyudmila Mashonkina

Comments: 15 pages, 9 figures, 9 tables, accepted for publication in MNRAS

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

A comprehensive model atom was developed for Si I-II-III using the most up-to-date atomic data available so far. Based on the non-local thermodynamic equilibrium (non-LTE = NLTE) line formation for Si I, Si II, and Si III and high-resolution observed spectra, we determined the NLTE abundances for a sample of nine unevolved A9 to B3-type stars with well determined atmospheric parameters. For each star, NLTE reduces substantially the line-to-line scatter for Si II compared with the LTE case and leads to consistent mean abundances from lines of different ionisation stages. In the hottest star of our sample, $\iota$ Her, Si II is subject to overionisation that drives emission in the lines arising from the high-excitation (above 12.5 eV) doublet levels. Our NLTE calculations reproduced 10 emission lines of Si II observed in $\iota$ Her. The same overionisation effect leads to greatly weakened Si II lines, which are observed in absorption in $\iota$ Her. Large positive NLTE abundance corrections (up to 0.98 dex for 5055 A) were useful for achieving consistent mean abundances from lines of the two ionisation stages, Si II and Si III. It was found that the NLTE effects are overestimated for the Si II 6347, 6371 A doublet in $\iota$ Her, while the new model atom works well for the cooler stars. At this stage, we failed to understand this problem. We computed for a grid of the NLTE abundance corrections for lines of Si I, Si II, and Si III in the model atmospheres with effective temperatures and surface gravities characteristic of unevolved A-B type stars.

[41]  arXiv:2003.01613 [pdf, ps, other]

Title: Molecular clumps disguising their star formation efficiency per freefall time: What we can do not to be fooled

Authors: Genevieve Parmentier

Comments: 11 pages, 6 figures, accepted for publication in ApJ

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

The presence of a volume density gradient in molecular clumps allow them to raise their star formation rate compared to what they would experience were their gas uniform in density. This higher star formation rate yields in turn a higher value for the star formation efficiency per freefall time that we measure. The measured star formation efficiency per freefall time $\epsilon_{\rm ff, meas}$ of clumps is therefore plagued by a degeneracy, as two factors contribute to it: one is the density gradient of the clump gas, the other is the intrinsic star formation efficiency per freefall time $\epsilon_{\rm ff, int}$ with which the clump would form stars should there be no gas density gradient. This paper presents a method allowing one to recover the intrinsic efficiency of a centrally-concentrated clump. It hinges on the relation between the surface densities in stars and gas measured locally from clump center to clump edge. Knowledge of the initial density profile of the clump gas is not required. A step-by-step description of the method is provided as a tool in hand for observers. Once $\epsilon_{\rm ff, int}$ has been estimated, it can be compared with its measured, clump-averaged, counterpart $\epsilon_{\rm ff, meas}$ to quantify the impact that the initial gas density profile of a clump has had on its star formation history.

[42]  arXiv:2003.01644 [pdf, other]

Title: The Imprint of the Protoplanetary Disk in the Accretion of Super-Earth Envelopes

Authors: Mohamad Ali-Dib, Andrew Cumming, Douglas N. C. Lin

Comments: 10 pages, 6 figures, resubmitted to MNRAS following the referee's report

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

Super-Earths are by far the most dominant type of exoplanet, yet their formation is still not well understood. In particular, planet formation models predict that many of them should have accreted enough gas to become gas giants. Here we examine the role of the protoplanetary disk in the cooling and contraction of the protoplanetary envelope. In particular, we investigate the effects of 1) the thermal state of the disk as set by the relative size of heating by accretion or irradiation, and whether its energy is transported by radiation or convection, and 2) advection of entropy into the outer envelope by disk flows that penetrate the Hill sphere, as found in 3D global simulations. We find that, at 5 and 1 AU, this flow at the level reported in the non-isothermal simulations where it penetrates only to ~ 0.3 times the Hill radius has little effect on the cooling rate since most of the envelope mass is concentrated close to the core, and far from the flow. On the other hand, at 0.1 AU, the envelope quickly becomes fully-radiative, nearly isothermal, and thus cannot cool down, stalling gas accretion. This effect is significantly more pronounced in convective disks, leading to envelope mass orders of magnitude lower. Entropy advection at 0.1 AU in either radiative or convective disks could therefore explain why super-Earths failed to undergo runaway accretion. These results highlight the importance of the conditions and energy transport in the protoplanetary disk for the accretion of planetary envelopes.

[43]  arXiv:2003.01650 [pdf, ps, other]

Title: ALMA 50-parsec resolution imaging of jet-ISM interaction in the lensed quasar MGJ0414+0534

Authors: Kaiki Taro Inoue, Satoki Matsushita, Kouichiro Nakanishi, Takeo Minezaki

Comments: 7 pages, 4 figures, accepted for publication in ApJ Letters

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

We report our high-resolution (0.03 arcsec to 0.07 arcsec) ALMA imaging of the quadruply lensed radio-loud quasar MG\,J0414+0534 at redshift $z=2.639$ in the continuum and the broad CO(11-10) line at $\sim 340\,$GHz. With the help of strong lensing magnification and ALMA's high-resolution, we succeeded in resolving the jet/dust and CO gas in the quasar host galaxy both extending up to $\sim 1\,$kpc, with a resolution of $\sim 50\,$pc for the first time. Both the continuum emission and the CO(11-10) line have a similar bimodal structure aligned with the quasar jets ($\sim 200\,$pc) observed by Very Long Baseline Interferometry (VLBI) at $5\,$GHz and $8.4\,$GHz. The CO gas in the vicinity of both the eastern and western jet components at the location of $\sim 80\,$pc from the quasar core are moving at high velocities up to $\pm 600\,$$\textrm{km}\,\textrm{s}^{-1}$ relative to the core. The observed features show clear evidence of strong interaction between the jets and interstellar medium (ISM). High temperature and high density environments in the ISM of the quasar host galaxy, as suggested from CO line ratios, also support this result. The small scale of the jets, the jet-ISM interaction, and the continuum spectral energy distribution of this source indicate that we are watching the infancy stage of quasar radio activity.

[44]  arXiv:2003.01698 [pdf, other]

Title: Energy and helicity fluxes in line-tied eruptive simulations

Authors: Luis Linan, Étienne Pariat, Guillaume Aulanier, Kostas Moraitis, Gherardo Valori

Comments: 18 pages, 9 figures, accepted for publication in Astronomy & Astrophysics

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

Based on a decomposition of the magnetic field into potential and nonpotential components, magnetic energy and relative helicity can both also be decomposed into two quantities: potential and free energies, and volume-threading and current-carrying helicities. In this study, we perform a coupled analysis of their behaviors in a set of parametric 3D magnetohydrodynamic (MHD) simulations of solar-like eruptions. We present the general formulations for the time-varying components of energy and helicity in resistive MHD. We calculated them numerically with a specific gauge, and compared their behaviors in the numerical simulations, which differ from one another by their imposed boundary-driving motions. Thus, we investigated the impact of different active regions surface flows on the development of the energy and helicity-related quantities. Despite general similarities in their overall behaviors, helicities and energies display different evolutions that cannot be explained in a unique framework. While the energy fluxes are similar in all simulations, the physical mechanisms that govern the evolution of the helicities are markedly distinct from one simulation to another: the evolution of volume-threading helicity can be governed by boundary fluxes or helicity transfer, depending on the simulation. The eruption takes place for the same value of the ratio of the current-carrying helicity to the total helicity in all simulations. However, our study highlights that this threshold can be reached in different ways, with different helicity-related processes dominating for different photospheric flows. This means that the details of the pre-eruptive dynamics do not influence the eruption-onset helicity-related threshold. Nevertheless, the helicity-flux dynamics may be more or less efficient in changing the time required to reach the onset of the eruption.

Cross-lists for Wed, 4 Mar 20

[45]  arXiv:2001.05791 (cross-list from physics.comp-ph) [pdf, other]

Title: Investigating the use of field solvers for simulating classical systems

Authors: Andrew Eberhardt, Arka Banerjee, Michael Kopp, Tom Abel

Comments: 28 pages, 14 figures. Matches published version Phys. Rev. D

Journal-ref: Phys. Rev. D 101, 043011 (2020)

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

We explore the use of field solvers as approximations of classical Vlasov-Poisson systems. This correspondence is investigated in both electrostatic and gravitational contexts. We demonstrate the ability of field solvers to be excellent approximations of problems with cold initial condition into the non linear regime. We also investigate extensions of the Schr\"odinger-Poisson system that employ multiple stacked cold streams, and the von Neumann-Poisson equation as methods that can successfully reproduce the classical evolution of warm initial conditions. We then discuss how appropriate simulation parameters need to be chosen to avoid interference terms, aliasing, and wave behavior in the field solver solutions. We present a series of criteria clarifying how parameters need to be chosen in order to effectively approximate classical solutions.

[46]  arXiv:2003.01038 (cross-list from gr-qc) [pdf, ps, other]

Title: Gravitational couplings in Chameleon models

Authors: Macarena Lagos, Hanjue Zhu

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

We consider cosmological models where dark energy is described by a dynamical field equipped with the Chameleon screening mechanism, which serves to hide its effects in local dense regions and to conform to Solar System observations. In these models, there is no universal gravitational coupling and here we study the effective couplings that determine the force between massive objects, $G_N$, and the propagation of gravitational waves, $G_{gw}$. In particular, we revisit the Chameleon screening mechanism without neglecting the time dependence of the galactic environment where local regions are embedded in, and analyze the induced time evolution on $G_N$ and $G_{gw}$, which can be tested with Lunar Laser Ranging and direct gravitational waves observations. We explicitly show how and why these two couplings generically differ. We also find that due to the particular way the Chameleon screening mechanism works, their time evolutions are highly suppressed in the weak-field non-relativistic approximation.

[47]  arXiv:2003.01188 (cross-list from gr-qc) [pdf, ps, other]

Title: Quasinormal modes, stability and shadows of a black hole in the novel 4D Einstein-Gauss-Bonnet gravity

Authors: R. A. Konoplya, A. F. Zinhailo

Comments: RevTex, 6 pages, 4 figures

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

Recently [D.~Glavan and C.~Lin, Phys.\ Rev.\ Lett.\ {\bf 124}, 081301 (2020)] a non-trivial $(3+1)$-dimensional Einstein-Gauss-Bonnet theory of gravity was formulated which bypasses the Lovelock's theorem and avoids Ostrogradsky instability. Here we calculate quasinormal modes of scalar, electromagnetic and gravitational perturbations and find the radius of shadow for spherically symmetric and asymptotically flat black holes in this theory. We have shown that the damping rate is more sensitive characteristic than the real oscillation frequency: it leads to considerable deviation from the Schwarzschild limit by tens of percents. We show that the coupling constant must be relatively small in order to avoid dynamical instabilities in the gravitational sector. The radius of the shadow $R_{Sh}$ obeys the linear law $R_{Sh} \approx (3 \sqrt{3}/2) + 0.94 \alpha$ with a remarkable accuracy.

[48]  arXiv:2003.01198 (cross-list from physics.hist-ph) [pdf, other]

Title: Archaeoastronomical study of the historic churches of La Gomera

Authors: Adrian Di Paolo, Alejandro Gangui

Comments: Article in Spanish including 8 figures. Published version available at this http URL

Journal-ref: Anales AFA 29:62-68, 2018

Subjects: History and Philosophy of Physics (physics.hist-ph); Instrumentation and Methods for Astrophysics (astro-ph.IM)

In this paper we discuss the importance of studying the orientation of ancient Christian churches, as a complement to the historical and cultural research of the temples. We present preliminary results of the analysis of the precise spatial orientation of 38 colonial churches located on the Canary Island of La Gomera (Spain). The sample suggests that, although several churches have a canonical orientation within the solar range, a large proportion of them follow a pattern of orientations that is compatible with the steep orography of the island and, therefore, contrasts with the prescriptions contained in the texts of the early Christian writers.

[49]  arXiv:2003.01252 (cross-list from gr-qc) [pdf, other]

Title: Quasi-periodic oscillations from the accretion disk around distorted black holes

Authors: Efthimia Deligianni, Jutta Kunz, Petya Nedkova

Comments: 24 pages, 8 figures

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

We study the quasi-periodic oscillations from the accretion disk around the distorted Schwarzschild black hole in the framework of the resonant models. We confine ourselves to the case of a quadrupole distortion which can be caused for example by the accreting matter flow in the vicinity of the compact object. For the purpose we examine the linear stability of the circular geodesic orbits in the equatorial plane and derive analytical expressions for the radial and vertical epicyclic frequencies. We investigate their properties in comparison with the isolated Schwarzschild black hole. Due to the influence of the external matter the vertical epicyclic frequency is not always positive anymore, and the stability of the circular orbits is determined by the interplay between both of the frequencies. As a result, the stable circular orbits do not extend to infinity, but are confined to a finite annular region between an inner and an outer marginally stable orbit. In addition, the degeneracy between the vertical epicyclic and the orbital frequency, which is characteristic for the Schwarzschild solution, is broken, and there are regions in the parametric space where the radial epicyclic frequency is larger than the vertical one. All these properties allow for much more diverse types of non-linear resonances to be excited than for the isolated Schwarzschild black hole, which can provide an explanation for the observed 3:2 ratio between the twin-peak frequencies of the quasi-periodic oscillations from the accretion disk.

[50]  arXiv:2003.01542 (cross-list from gr-qc) [pdf, other]

Title: On the Expected Backreaction During Preheating

Authors: C. Armendariz-Picon

Comments: 41 pages, 10 figures

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

In previous work we argued that the correct procedure to predict the gravitational wave signal from preheating after inflation rests on the in-in formalism. We extend here our previous analysis to include the backreaction of the produced matter on the motion of the inflaton and the expansion of the universe, and study how the latter affect the spectrum of the resulting gravitational waves. The addition of backreaction demands the appropriate renormalization of divergent expectation values, which we regularize by preserving diffeomorphism invariance in a manner that is amenable to numerical integration. The very same calculation also allows us to determine for which strength of the inflaton to matter couplings reheating is successful. We illustrate our results with the scalar version of the Starobinsky model of inflation, and observe that it is hard to reheat the universe while keeping radiative corrections under control.

[51]  arXiv:2003.01692 (cross-list from gr-qc) [pdf, other]

Title: Fourth post-Newtonian Hamiltonian dynamics of two-body systems from an effective field theory approach

Authors: J. Blümlein, A. Maier, P. Marquard, G. Schäfer

Comments: 28 pages, 2 Figures

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

We calculate the motion of binary mass systems in gravity up to the fourth post--Newtonian order. We use momentum expansions within an effective field theory approach based on Feynman amplitudes in harmonic coordinates by applying dimensional regularization. We construct the canonical transformations to ADM coordinates and to effective one body theory (EOB) to compare with other approaches. We show that intermediate poles in the dimensional regularization parameter $\varepsilon$ vanish in the observables and the classical theory is not renormalized. The results are illustrated for a series of observables for which we agree with the literature.

Replacements for Wed, 4 Mar 20

[52]  arXiv:1902.08374 (replaced) [pdf, other]

Title: Constraints of general screened modified gravities from comprehensive analysis of binary pulsars

Authors: Xing Zhang, Wen Zhao, Tan Liu, Kai Lin, Chao Zhang, Xiang Zhao, Shaojun Zhang, Tao Zhu, Anzhong Wang

Comments: 14 pages, 20 figures, 2 tables, Astrophysical. J. 874 (2019) 121 (11 pages)

Journal-ref: Astrophysical. J. 874 (2019) 121

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

[53]  arXiv:1906.03566 (replaced) [pdf, ps, other]

Title: Energy extraction and particle acceleration around a rotating dyonic black hole in $N=2$, $U(1)^2$ gauged supergravity

Authors: Anik Rudra, Hemwati Nandan, Radouane Gannouji, Soham Chakraborty, Arindam Kumar Chatterjee

Comments: 17 pages, 11 figures, 8 tables. Some major corrections are made along with the corrections of few typos

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

[54]  arXiv:1908.10874 (replaced) [pdf, other]

Title: Characterizing the Nature of the Unresolved Point Sources in the Galactic Center

Authors: Laura J. Chang, Siddharth Mishra-Sharma, Mariangela Lisanti, Malte Buschmann, Nicholas L. Rodd, Benjamin R. Safdi

Comments: 21+16 pages, 10+17 figures

Journal-ref: Phys. Rev. D 101, 023014 (2020)

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

[55]  arXiv:1909.01033 (replaced) [pdf, other]

Title: Disc galaxies formed from major mergers in Illustris

Authors: Nicolas Peschken, Ewa L. Łokas, E. Athanassoula

Comments: 14 pages, 14 figures, 1 table, accepted for publication in MNRAS

Journal-ref: Monthly Notices of the Royal Astronomical Society, Volume 493, Issue 1, March 2020, Pages 1375-1387

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

[56]  arXiv:1909.11267 (replaced) [pdf, other]

Title: Search for ultralight bosons in Cygnus X-1 with Advanced LIGO

Authors: Ling Sun, Richard Brito, Maximiliano Isi

Comments: 9 pages, 4 figures

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

[57]  arXiv:1910.07317 (replaced) [pdf, ps, other]

Title: Machine-learning computation of distance modulus for local galaxies

Authors: A. Elyiv, O. Melnyk, I. Vavilova, D. Dobrycheva, V. Karachentseva

Comments: 8 pages, 5 figures, Accepted for publication in A&A

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

[58]  arXiv:1911.03473 (replaced) [pdf, other]

Title: Non-equilibrium antineutrinos of primordial nucleosynthesis

Authors: Vlad Yu. Yurchenko, Alexandre V. Ivanchik

Comments: 16 pages, 6 figures

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

[59]  arXiv:1911.11513 (replaced) [pdf, other]

Title: Reheating in $R^2$ Palatini inflationary models

Authors: Ioannis D. Gialamas, A. B. Lahanas

Comments: 38 pages, 14 figures, pdflatex, text, figures and references added, formulas updated

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

[60]  arXiv:1912.01626 (replaced) [pdf, other]

Title: The rest-frame UV luminosity function at $z \simeq 4$: a significant contribution of AGN to the bright-end of the galaxy population

Authors: N. J. Adams, R. A. A. Bowler, M. J. Jarvis, B. Häußler, R. J. McLure, A. Bunker, J. S. Dunlop, A. Verma

Comments: 14 pages, 9 figures, 3 tables, Updated to match MNRAS accepted version (accepted 3/3/2020) after minor revisions

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

[61]  arXiv:2001.00421 (replaced) [pdf, other]

Title: Interpretation of ALMA velocity map for the obscuring torus in NGC1068

Authors: E.Yu. Bannikova, N.A. Akerman, A.V. Sergeyev

Comments: 10 pages, 3 figures

Journal-ref: Astronomical and Astrophysical Transactions, vol.31, issue 4, 2020

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

[62]  arXiv:2001.05791 (replaced) [pdf, other]

Title: Investigating the use of field solvers for simulating classical systems

Authors: Andrew Eberhardt, Arka Banerjee, Michael Kopp, Tom Abel

Comments: 28 pages, 14 figures. Matches published version Phys. Rev. D

Journal-ref: Phys. Rev. D 101, 043011 (2020)

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

[63]  arXiv:2001.09933 (replaced) [pdf, other]

Title: Cosmic-ray interactions with the Sun using the FLUKA code

Authors: M. N. Mazziotta, P. De La Torre Luque, L. Di Venere, A. Fassò, A. Ferrari, F. Loparco, P. R. Sala, D.Serini

Comments: 13 pages, 13 figures, accepted for publication in PRD

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

[64]  arXiv:2001.11893 (replaced) [pdf, ps, other]

Title: Expression of the Holtsmark function in terms of hypergeometric $_2F_2$ and Airy $\mathrm{Bi}$ functions

Authors: Jean-Christophe Pain

Subjects: Mathematical Physics (math-ph); Astrophysics of Galaxies (astro-ph.GA); Atomic Physics (physics.atom-ph)

[65]  arXiv:2002.02978 (replaced) [pdf, ps, other]

Title: The X-Ray Cavity Around Hotspot E in Cygnus A: Tunneled by a Deflected Jet

Authors: Bradford Snios, Amalya C. Johnson, Paul E. J. Nulsen, Ralph P. Kraft, Martijn de Vries, Richard A. Perley, Lerato Sebokolodi, Michael W. Wise

Comments: Accepted to ApJ, 12 pages, 7 figures, 5 tables

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

[66]  arXiv:2002.10195 (replaced) [pdf, other]

Title: ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT): I. CO, CS, CN, and H2CO around DG Tau B

Authors: Antonio Garufi, Linda Podio, Claudio Codella, Kazi Rygl, Francesca Bacciotti, Stefano Facchini, Davide Fedele, Anna Miotello, Richard Teague, Leonardo Testi

Comments: 13 pages, 6 figures, accepted by A&A

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

[67]  arXiv:2002.10762 (replaced) [pdf, other]

Title: Fourth-order Coronagraph for High-Contrast Imaging of Exoplanets with Off-axis Segmented Telescopes

Authors: Satoshi Itoh, Taro Matsuo

Comments: Resubmitted to AJ after revision from referee's report; typos corrected

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

[68]  arXiv:2002.10884 (replaced) [pdf, other]

Title: Constraints on the symmetry energy and its associated parameters from nuclei to neutron stars

Authors: Yingxun Zhang, Min Liu, Cheng-Jun Xia, Zhuxia Li, Subrata Kumar Biswal

Comments: 10 pages, 11 figures, 2 tables, accepted by Phys.Rev.C. This article draws heavily from arXiv:1911.05380. In the v1 version, we modified two typos in Table II

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

[69]  arXiv:2002.11091 (replaced) [pdf, ps, other]

Title: Precise determination of the inflationary epoch and constraints for reheating

Authors: Gabriel German

Comments: 4 pages, no figures. The main equation Eq.(4) has been replaced by a more compact looking formula, although equivalent to the originally presented. The numbers in Eqs.(24)-(27) have been adjusted after a calculation with improved precision

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

[70]  arXiv:2003.00986 (replaced) [pdf, other]

Title: Stochastic Calibration of Radio Interferometers

Authors: Sarod Yatawatta

Comments: MNRAS Accepted 2020 March 2. Received 2020 March 2 ; in original form 2020 January 27

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Artificial Intelligence (cs.AI); Distributed, Parallel, and Cluster Computing (cs.DC)

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