Astrophysics
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New submissions for Fri, 7 Feb 20
- [1] arXiv:2002.01926 [pdf, other]
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Title: Curvature of magnetic field lines in compressible magnetized turbulence: Statistics, magnetization predictions, gradient curvature, modes and self-gravitating mediaComments: 15 pages, 7 figures, submitted to ApJSubjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Magnetic field lines in interstellar media have a rich morphology, which could be characterized by geometrical parameters such as curvature and torsion. In this paper, we explore the statistical properties of magnetic field line curvature $\kappa$ in compressible magnetized turbulence. We see that both the mean and standard deviation of magnetic field line curvature obey power-law relations to the magnetization. Moreover, the power-law tail of the curvature probability distribution function is also proportional to the Alfvenic Mach number. We also explore whether the curvature method could be used in the field-tracing Velocity Gradient Technique. In particular, we observe that there is a relation between the mean and standard deviation of the curvature probed by velocity gradients to $M_A$. Finally we discuss how curvature is contributed by different MHD modes in interstellar turbulence, and suggests that the eigenvectors of MHD modes could be possibly represented by the natural Fernet-Serrat frame of the magnetic field lines. We discuss possible theoretical and observational applications of the curvature technique, including the extended understanding on a special length scale that characterize the importance of magnetic field curvature in driving MHD turbulence, and how it could be potentially used to study self-gravitating system.
- [2] arXiv:2002.01933 [pdf, other]
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Title: Dust entrainment in galactic windsAuthors: Rahul Kannan (1), Mark Vogelsberger (2), Federico Marinacci (3), Laura V. Sales (4), Paul Torrey (5), Lars Hernquist (1) ((1) Harvard, (2) MIT, (3) U Bologna, (4) UCR, (5) UFL)Comments: 6 pages, 4 figures, submitted to ApJL, Comments welcomeSubjects: Astrophysics of Galaxies (astro-ph.GA)
Winds driven by stellar feedback are an essential part of the galactic ecosystem and are the main mechanism through which low-mass galaxies regulate their star formation. These winds are generally observed to be multi-phase with detections of entrained neutral and molecular gas. They are also thought to enrich the circum-galactic medium around galaxies with metals and dust. This ejected dust encodes information about the integrated star formation and outflow history of the galaxy. It is therefore, important to understand how much dust is entrained and driven out of the disc by galactic winds. Here we demonstrate that stellar feedback is efficient in driving dust-enriched winds and eject enough material to account for the amount of extraplanar dust observed in nearby galaxies. The amount of dust in the wind depends on the sites from where they are launched, with dustier galaxies launching more dust enriched outflows. Moreover, the outflowing cold-dense gas is significantly more dust-enriched than the volume filling hot tenuous material, naturally reproducing the complex multiphase structure of the outflowing wind observed in nearby galaxies. These results provide an important new insight into the dynamics, structure, and composition of galactic winds and their role in determining the dust content of the extragalactic gas in galaxies.
- [3] arXiv:2002.01934 [pdf, other]
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Title: Scatter in Sunyaev--Zel'dovich effect scaling relations explained by inter-cluster variance in mass accretion historiesComments: 18 pages, 10 figures, submitted to MNRASSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)
The X-ray and microwave observable-mass scaling relations of galaxy clusters are immensely valuable tools for cosmological analysis, but their power is currently limited by astrophysical systematic uncertainties that bias cluster mass estimates and introduce additional scatter. Turbulent energy injected into the intracluster medium via mass assembly contributes substantially to the cluster's non-thermal pressure support, which is a significant source of such uncertainties. We use a simple analytical model to compute the mass assembly-driven non-thermal pressure profiles of individual haloes based on Monte Carlo-generated halo assembly histories from extended Press--Schechter theory. After combining this with the Komatsu--Seljak model for the total pressure to obtain thermal pressure profiles, we predict deviations from self-similarity and the intrinsic scatter in the Sunyaev--Zel'dovich effect observable-mass scaling relation ($Y_\mathrm{SZ}-M$) due solely to inter-cluster variations in halo mass assembly histories. We study the dependence of the slope, normalization, and scatter of $Y_\mathrm{SZ}-M$ on aperture radius, cosmology, redshift, and halo mass limit. The model predicts $5-9\%$ scatter in $Y_\mathrm{SZ}-M$ at $z=0$, increasing as the aperture used to compute $Y_\mathrm{SZ}$ increases from $r_\mathrm{500c}$ to $5r_\mathrm{500c}$. The predicted scatter lies slightly below that of studies based on non-radiative hydrodynamical simulations, illustrating that assembly history variance alone is likely to be responsible for a substantial fraction of the scatter in $Y_\mathrm{SZ}-M$. As redshift increases, $Y_\mathrm{SZ}-M$ deviates more from self-similarity and scatter increases. Lastly, we show that the residuals of $Y_\mathrm{SZ}-M$ correlate strongly with the recent halo mass accretion rate, potentially providing an opportunity to infer the latter.
- [4] arXiv:2002.01936 [pdf, other]
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Title: The frequency of gaseous debris discs around white dwarfsAuthors: Christopher J. Manser, Boris T. Gänsicke, Nicola Pietro Gentile Fusillo, Richard Ashley, Elmé Breedt, Mark Hollands, Paula Izquierdo, Ingrid PelisoliComments: 13 pages, 6 Figures, accepted for publication in MNRASSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
1-3 per cent of white dwarfs are orbited by planetary dusty debris detectable as infrared emission in excess above the white dwarf flux. In a rare subset of these systems, a gaseous disc component is also detected via emission lines of the Ca II 8600\r{A} triplet, broadened by the Keplerian velocity of the disc. We present the first statistical study of the fraction of debris discs containing detectable amounts of gas in emission at white dwarfs within a magnitude and signal-to-noise limited sample. We select 7705 single white dwarfs spectroscopically observed by the Sloan Digital Sky Survey (SDSS) and $Gaia$ with magnitudes $g$ $\leq$ 19. We identify five gaseous disc hosts, all of which have been previously discovered. We calculate the occurrence rate of a white dwarf hosting a debris disc detectable via Ca II emission lines as 0.067$\pm$$_{0.025}^{0.042}$ per cent. This corresponds to an occurrence rate for a dusty debris disc to have an observable gaseous component in emission as 4$\pm$$_{2}^{4}$ per cent. Given that variability is a common feature of the emission profiles of gaseous debris discs, and the recent detection of a planetesimal orbiting within the disc of SDSSJ122859.93+104032.9, we propose that gaseous components are tracers for the presence of planetesimals embedded in the discs and outline a qualitative model. We also present spectroscopy of the Ca II triplet 8600\r{A} region for 20 white dwarfs hosting dusty debris discs in an attempt to identify gaseous emission. We do not detect any gaseous components in these 20 systems, consistent with the occurrence rate that we calculated.
- [5] arXiv:2002.01937 [pdf, other]
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Title: Universality and Non-Universality in Distributed Nuclear Burning in Homogeneous Isotropic TurbulenceComments: Submitted, comments welcomeSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th); Fluid Dynamics (physics.flu-dyn)
Nuclear burning plays a key role in a wide range of astrophysical stellar transients, including thermonuclear, pair instability, and core collapse supernovae, as well as kilonovae and collapsars. Turbulence is now understood to also play a key role in these astrophysical transients. Here we demonstrate that turbulent nuclear burning may lead to large enhancements above the uniform background burning rate, since turbulent dissipation gives rise to temperature fluctuations, and in general the nuclear burning rates are highly sensitive to temperature. We derive results for the turbulent enhancement of the nuclear burning rate under the influence of strong turbulence in the distributed burning regime in homogeneous isotropic turbulence, using probability distribution function (PDF) methods. We demonstrate that the turbulent enhancement obeys a universal scaling law in the limit of weak turbulence. We further demonstrate that, for a wide range of key nuclear reactions, such as C$^{12}$(O$^{16}$, $\alpha$)Mg$^{24}$ and triple-$\alpha$, even relatively modest temperature fluctuations, of the order ten percent, can lead to enhancements of 1 - 3 orders of magnitude in the turbulent nuclear burning rate. We verify the predicted turbulent enhancement directly against numerical simulations, and find very good agreement. We also present an estimation for the onset of turbulent detonation initiation, and discuss implications of our results for the modeling of stellar transients.
- [6] arXiv:2002.01938 [pdf, other]
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Title: First Results on Dark Matter Substructure from Astrometric Weak LensingComments: 9 pages, 11 figuresSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)
Low-mass structures of dark matter (DM) are expected to be entirely devoid of light-emitting regions and baryons. Precisely because of this lack of baryonic feedback, small-scale substructures of the Milky Way are a relatively pristine testing ground for discovering aspects of DM microphysics and primordial fluctuations on subgalactic scales. In this work, we report results from the first search for Galactic DM subhalos with time-domain astrometric weak gravitational lensing. The analysis is based on a matched-filter template of local lensing corrections to the proper motion of stars in the Magellanic Clouds. We describe a data analysis pipeline detailing sample selection, background subtraction, and handling outliers and other systematics. For tentative candidate lenses, we identify a signature based on an anomalous parallax template that can unequivocally confirm the presence of a DM lens, opening up prospects for robust discovery potential with full time-series data. We present our constraints on substructure fraction $f_l \lesssim 5$ at 90% CL (and $f_l \lesssim 2$ at 50% CL) for compact lenses with radii $r_l < 1\,\mathrm{pc}$, with best sensitivity reached for lens masses $M_l$ around $10^7$-$10^8\,M_\odot$. Parametric improvements are expected with future astrometric data sets; by end of mission, $Gaia$ could reach $f_l \lesssim 10^{-3}$ for these massive point-like objects, and be sensitive to lighter and/or more extended subhalos for $\mathcal{O}(1)$ substructure fractions.
- [7] arXiv:2002.01939 [pdf, ps, other]
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Title: Advection by large-scale spiral flows in galaxy clustersComments: 18 pages, 10 figures, 3 tables; comments welcomeSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
The intracluster medium of a galaxy cluster often shows an extended quasi-spiral structure, accentuated by tangential discontinuities known as cold fronts (CFs). These discontinuities are thought to isolate between low-entropy, high-metallicity gas inside (i.e., below) the CF that was lifted from the center of the cluster by some radial factor $f_i$, and high-entropy, low-metallicity gas outside the CF that was pushed inward by a factor $f_o$. We find broad support for such a picture, by comparing the entropy and metallicity discontinuities with the respective azimuthal averages, using newly deprojected thermal profiles in clusters A2029, A2142, A2204 and Centaurus, supplemented by deprojected CFs from the literature. In particular, the mean advection factors $f_K$ and $f_Z$, inferred respectively from entropy and metallicity, strongly correlate ($\mathcal{R}=0.7^{+0.2}_{-0.3}$) with each other, consistent with large-scale advection. However, unlike sloshing simulations, in which the inside/outside phases are an inflow/outflow settling back to equilibrium after a violent perturbation, our results are more consistent with an outflow/inflow, with the fast, Mach $\mathcal{M}_i\sim0.8$ gas inside the CF being a rapidly heated or mixed outflow, probably originating from the cD galaxy, and gas outside the CF being a $\mathcal{M}_o\sim0.03$, slowly-cooling inflow. In particular, entropy indicates an outside advection factor $f_{Ko}\simeq 1.33\pm0.04$ that is approximately constant in all CFs, gauging the distance traversed by inflowing gas within a cooling time. In contrast, $1.1\lesssim f_{Ki}\lesssim 2.5$ and $1\lesssim f_Z\lesssim 17$ vary considerably among clusters, and strongly correlate ($3.1\sigma\text{-}4.2\sigma$) with the virial mass, $f_{Ki}\propto M_{200}^{0.14\pm0.07}$ and $f_Z\propto M_{200}^{1.4\pm0.4}$, suggesting that each cluster sustains a quasi-steady spiral flow.
- [8] arXiv:2002.01940 [pdf, other]
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Title: A robust two-parameter description of the stellar profile of elliptical galaxiesAuthors: Alessandro Sonnenfeld (Leiden Observatory)Comments: 13 pages, 13 figures, submitted to Astronomy & AstrophysicsSubjects: Astrophysics of Galaxies (astro-ph.GA)
The stellar density profile a galaxy is typically summarised with two numbers: total stellar mass and half-light radius. The total mass of a galaxy, however, is not a well-defined quantity, due to the finite depth of photometric observations and the arbitrariness of the distinction between galaxy and diffuse intra-group light. This limits our ability to make accurate comparisons between models and observations. I wish to provide a more robust two-parameter description of the stellar density distribution of elliptical galaxies, in terms of quantities that can be measured unambiguously. I propose to use the stellar mass enclosed within 10 kpc in projection, $M_{*,10}$, and the mass-weighted stellar density slope within the same aperture, $\Gamma_{*,10}$, for this purpose. I measured the distribution in $M_{*,10}$ and $\Gamma_{*,10}$ of a sample of elliptical galaxies from the Sloan Digital Sky Survey and the Galaxy And Mass Assembly survey, using photometry from the Hyper Suprime-Cam survey. The pair of values of $(M_{*,10},\Gamma_{*,10})$ can be used to predict the stellar density profile in the inner 10 kpc of a galaxy with better than 20% accuracy. Similarly, $M_{*,10}$ and $\Gamma_{*,10}$ can be combined to obtain a proxy for stellar velocity dispersion at least as good as the stellar mass fundamental plane. As a first application, I then compared the observed $M_{*,10}-\Gamma_{*,10}$ relation of elliptical galaxies with that of similarly selected galaxies in the EAGLE Reference simulation. Observed and simulated galaxies match at $M_{*,10}=10^{11}M_\odot$, but the EAGLE $M_{*,10}-\Gamma_{*,10}$ relation is shallower and has a larger intrinsic scatter compared to observations. This new parameterisation of the stellar density profile of massive elliptical galaxies provides a more robust way of comparing results from different photometric surveys and from hydrodynamical simulations.
- [9] arXiv:2002.01941 [pdf, other]
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Title: The formation of exponential disk galaxies in MONDComments: For movies of the formation of these galaxies see Youtube entry:"Formation of disk galaxies in MOND by Nils Wittenburg"Subjects: Astrophysics of Galaxies (astro-ph.GA)
The formation and evolution of galaxies is highly dependent on the dynamics of stars and gas, which is governed by the underlying law of gravity. To investigate how the formation and evolution of galaxies takes place in Milgromian gravity (MOND), we present full hydrodynamical simulations with the Phantom of Ramses (POR) code. These are the first-ever galaxy formation simulations done in MOND with detailed hydrodynamics, including star formation, stellar feedback, radiative transfer and supernovae. These models start from simplified initial conditions, in the form of isolated, rotating gas spheres in the early Universe. These collapse and form late-type galaxies obeying several scaling relations, which was not a priori expected. The formed galaxies have a compact bulge and a disk with exponentially decreasing surface mass density profiles and scale lengths consistent with observed galaxies, and vertical stellar mass distributions with distinct exponential profiles (thin and thick disk). This work thus shows for the first time that disk galaxies with exponential profiles in both gas and stars are a generic outcome of collapsing gas clouds in MOND. These models have a slight lack of stellar angular momentum because of their somewhat compact stellar bulge, which is connected to the simple initial conditions and the negligible later gas accretion. We also analyse how the addition of more complex baryonic physics changes the main resulting properties of the models and find this to be negligibly so in the Milgromian framework.
- [10] arXiv:2002.01943 [pdf, other]
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Title: Two intermediate-mass brown dwarfs from the TESS missionAuthors: Theron W. Carmichael, Samuel N. Quinn, Alexander J. Mustill, Chelsea Huang, George Zhou, Carina M. Persson, Louise D. Nielsen, Karen A. Collins, Carl Ziegler, Kevin I. Collins, Joseph E. Rodriguez, Avi Shporer, Rafael Brahm, Andrew W. Mann, Francois Bouchy, Malcolm Fridlund, Keivan G. Stassun, Coel Hellier, Julia V. Seidel, Manu Stalport, Stephane Udry, Francesco Pepe, Michael Ireland, Marusa Zerjal, Cesar Briceno, Nicholas Law, Andres Jordan, Nestor Espinoza, Thomas Henning, Paula Sarkis, David W. LathamComments: 18 pages, 10 figures, 8 tables, submitted to AJ; email: tcarmich@cfa.harvard.eduSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
We report the discovery of two intermediate-mass brown dwarfs (BDs), TOI-569b and TOI-1406b, from NASA's Transiting Exoplanet Survey Satellite mission. TOI-569b has an orbital period of $P = 6.55604 \pm 0.00016$ days, a mass of $M_b = 63.8 \pm 1.0 M_J$, and a radius of $R_b = 0.75 \pm 0.02 R_J$. Its host star, TOI-569, has a mass of $M_\star = 1.21 \pm 0.03 M_\odot$, a radius of $R_\star = 1.48 \pm 0.03 R_\odot$, and an effective temperature of $T_{\rm eff} = 5705 \pm 76K$. TOI-1406b has an orbital period of $P = 10.57415 \pm 0.00063$ days, a mass of $M_b =46.0 \pm 2.7 M_J$, and a radius of $R_b = 0.86 \pm 0.03 R_J$. The host star for this BD has a mass of $M_\star =1 .18 \pm 0.09 M_\odot$, a radius of $R_\star = 1.35 \pm 0.03 R_\odot$, and an effective temperature of $T_{\rm eff} = 6290 \pm 100K$. Both BDs are in circular orbits around their host stars and join an increasing number of known transiting intermediate-mass BDs. TOI-569 is one of two slightly evolved stars known to host a transiting BD (the other being KOI-415). TOI-1406b is one of three known transiting BDs to occupy the mass range of 40-50$M_J$ and one of two to have a circular orbit at a period near 10 days (with the first being KOI-205b). Based on the relatively long circularization timescales for both BDs, we believe that they must have formed in nearly circular orbits and migrated inward to their present orbital configurations.
- [11] arXiv:2002.01945 [pdf, other]
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Title: Evolution of the grain size distribution in galactic discsAuthors: M. Relano (1), U. Lisenfeld (1), K. C. Hou (2), I. De Looze (3), J.M. Vilchez (4), R. C. Kennicutt (5) ((1) University of Granada, (2) Ben-Gurion University of the Negev, (3) University of Ghent, (4) IAA-Spain, (5) University of Arizona)Comments: 11 pages, 6 Figures, to be published in A&ASubjects: Astrophysics of Galaxies (astro-ph.GA)
Dust is formed out of stellar material and is constantly affected by different mechanisms occurring in the ISM. Dust grains behave differently under these mechanisms depending on their sizes, and therefore the dust grain size distribution also evolves as part of the dust evolution itself. Following how the grain size distribution evolves is a difficult computing task that is just recently being overtaking. Smoothed particle hydrodynamic (SPH) simulations of a single galaxy as well as cosmological simulations are producing the first predictions of the evolution of the dust grain size distribution. We compare for the first time the evolution of the dust grain size distribution predicted by the SPH simulations with the results provided by the observations. We analyse how the radial distribution of the small to large grain mass ratio (D(S)/D(L)) changes over the whole discs in three galaxies: M 101, NGC 628 and M 33. We find good agreement between the observed radial distribution of D(S)/D(L) and what is obtained from the SPH simulations of a single galaxy. The central parts of NGC 628, at high metallicity and with a high molecular gas fraction, are mainly affected not only by accretion but also by coagulation of dust grains. The centre of M 33, having lower metallicity and lower molecular gas fraction, presents an increase of D(S)/D(L), showing that shattering is very effective in creating a large fraction of small grains. Observational results provided by our galaxies confirm the general relations predicted by the cosmological simulations based on the two grain size approximation. However, we present evidence that the simulations could be overestimating the amount of large grains in high massive galaxies.
- [12] arXiv:2002.01946 [pdf, other]
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Title: Discovery of a low-mass companion embedded in the disk of the young massive star MWC 297 with VLT/SPHEREAuthors: M. Giulia Ubeira-Gabellini, Valentin Christiaens, Giuseppe Lodato, Mario van den Ancker, Davide Fedele, Carlo F. Manara, Daniel J. PriceComments: 4 figuresSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
We report the discovery of a low-mass stellar companion around the young Herbig Be star MWC 297. We performed multi-epoch high-contrast imaging in the near infrared (NIR) with the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. The companion is found at projected separation of 244.7$\pm$13.2 au and a position angle of 176.4$\pm$0.1 deg. The large separation supports formation via gravitational instability. From the spectrum, we estimate a mass of 0.1-0.5 M$_{\odot}$, the range conveying uncertainties in the extinction of the companion and in evolutionary models at young ages. The orbit coincides with a gap in the dust disk inferred from the Spectral Energy Distribution (SED). The young age ($\lesssim$ 1 Myr) and mass ratio with the central star ($\sim 0.01$) makes the companion comparable to PDS 70~b, suggesting a relation between formation scenarios and disk dynamics.
- [13] arXiv:2002.01950 [pdf, other]
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Title: Observational constraints on the optical and near-infrared emission from the neutron star-black hole binary merger S190814bvAuthors: K. Ackley, L. Amati, C. Barbieri, F. E. Bauer, S. Benetti, M. G. Bernardini, K. Bhirombhakdi, M. T. Botticella, M. Branchesi, E. Brocato, S. H. Bruun, M. Bulla, S. Campana, E. Cappellaro, A. J. Castro-Tirado, K. C. Chambers, S. Chaty, T.-W. Chen, R. Ciolfi, A. Coleiro, C. M. Copperwheat, S. Covino, R. Cutter, F. D'Ammando, P. D'Avanzo, G. De Cesare, V. D'Elia, M. Della Valle, L. Denneau, M. De Pasquale, V. S. Dhillon, M. J. Dyer, N. Elias-Rosa, P. A. Evans, R. A. J. Eyles-Ferris, A. Fiore, M. Fraser, A. S. Fruchter, J. P. U. Fynbo, L. Galbany, C. Gall, D. K. Galloway, F. I. Getman, G. Ghirlanda, J. H. Gillanders, A. Gomboc, B. P. Gompertz, C. González-Fernández, S. González-Gaitán, A. Grado, G. Greco, M. Gromadzki, P. J. Groot, C. P. Gutiérrez, T. Heikkilä, et al. (99 additional authors not shown)Comments: 35 pages, submitted to A&A. Abstract abridged to meet arXiv requirementsSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
On 2019 August 14, the LIGO and Virgo interferometers detected a high-significance event labelled S190814bv, likely due to the merger of a compact binary system formed by a BH and a NS. In this paper, we present our extensive search campaign aimed at uncovering the potential optical/near infrared electromagnetic counterpart of S190814bv. We found no convincing electromagnetic counterpart in our data. ElectromagNetic counterparts of GRAvitational wave sources at the VEry Large Telescope (ENGRAVE) collaboration members carried out an intensive multi-epoch, multi-instrument observational campaign to identify the possible optical/near infrared counterpart of the event. In addition, the ATLAS, GOTO, GRAWITA-VST, Pan-STARRS and VINROUGE projects also carried out a search on this event. In this paper, we describe the combined observational campaign of these groups. The typical depth of our wide-field observations, which cover most of the projected sky localisation probability (from 33% to 99.8%, depending on the night and filter considered), is r~22 (resp. K~21) in the optical (resp. near infrared). We reach deeper limits in a subset of our galaxy-targeted observations, which cover a total ~50% of the galaxy-mass-weighted localisation probability. Altogether, our observations allow us to exclude a KN with large ejecta mass M>0.1 M$_\odot$ to a high ($>$90%) confidence, and we place meaningful limits on a larger portion of the ejecta mass parameter space. This disfavours the tidal disruption of the neutron star during the merger. Given the distance of S190814bv we could not reach sufficiently deep limits to constrain a KN comparable in luminosity to AT2017gfo on a large fraction of the local localisation probability. This suggests that future (likely common) events at a few hundreds Mpc will be detected only by large facilities with both high sensitivity and large field of view.
- [14] arXiv:2002.01954 [pdf, other]
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Title: Review of Pulsar Timing Array for Gravitational Wave ResearchAuthors: Pravin Kumar DahalComments: 8 pages, 4 figures; Accepted for publication in the Journal of Astrophysics and AstronomySubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
Ongoing research on Pulsar Timing Array (PTA) to detect gravitational radiation is reviewed. Here, we discuss the use of millisecond pulsars as a gravitational wave detector, the sources of gravitational radiation detectable by PTAs and the current status of PTA experiments pointing out the future possibilities.
- [15] arXiv:2002.01956 [pdf, other]
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Title: Constraining the Mass of the Emerging Galaxy Cluster SpARCS1049+56 at z= 1.71 with Infrared Weak LensingAuthors: Kyle Finner, M. James Jee, Tracy Webb, Gillian Wilson, Saul Perlmutter, Adam Muzzin, Jullie Hlavacek-LarrondoComments: 14 pages, 7 figures, submitted to ApJSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
In the hierarchical structure formation model of the universe, galaxy clusters are assembled through a series of mergers. Accordingly, it is expected that galaxy clusters in the early universe are actively forming and dynamically young. Located at a high redshift of z=1.71, SpARCS1049+56 offers a unique look into the galaxy cluster formation process. This cluster has been shown to be rich in cluster galaxies and to have intense star formation. Its high redshift pushes a weak-lensing analysis beyond the regime of the optical spectrum into that of the infrared. Equipped with deep Hubble Space Telescope Wide Field Camera 3 UVIS and IR observations, we present a weak-lensing characterization of SpARCS1049+56. As few IR weak-lensing studies have been performed, we discuss the details of PSF modeling and galaxy shape measurement for an IR weak-lensing procedure and the systematics that come with the territory. It will be critical to understand these systematics in future weak-lensing studies in the IR with the next generation space telescopes such as JWST, Euclid, and WFIRST. Through a careful analysis, the mass distribution of this young galaxy cluster is mapped and the convergence peak is detected at a 3.3 sigma level. The weak-lensing mass of the cluster is estimated to be $3.5\pm1.2\times10^{14}\ \text{M}_\odot$ and is consistent with the mass derived from a mass-richness scaling relation. This mass is extreme for a cluster at such a high redshift and suggests that SpARCS1049+56 is rare in the standard $\Lambda$CDM universe.
- [16] arXiv:2002.01970 [pdf, other]
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Title: Reply to: Overconfidence in Bayesian analyses of galaxy rotation curvesComments: 4 pages. The published version (in the Matters Arising section) can be freely accessed through this https URLJournal-ref: Nature Astronomy 2020Subjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
Cameron {\it et al.}~2019 (hereafter C19) recommends a more cautious and rigorous approach to statistical analysis in astronomy. We welcome this particular side of their communication as it helps stimulating the effort towards the adoption of better statistical methods in galaxy rotation curves, an effort to which we contributed with Rodrigues {\it et al.}~2018 (hereafter R18). Indeed, R18 was the first work that, in order to conclude on the universality of the acceleration scale $a_0$, studied the posterior distributions on $a_0$ of a large set of galaxies. As C19 agrees, the credible intervals were found within the Bayesian framework, that is, the marginalized posteriors on $a_0$ were found using Bayes' theorem to update the priors in light of the observational data; this process was done without introducing any approximation. Considering R18, C19 also remarks that: i) better methods to select the nuisance parameters and the corresponding priors could be used; ii) a quality cut based on $\chi^2$ values should not be used, and iii) the compatibility of the posteriors should be assessed in a more robust way. In the following, after first clarifying the context of our work, we address these criticisms.
- [17] arXiv:2002.01972 [pdf, ps, other]
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Title: Consistent Blandford-Znajek ExpansionSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
The Blandford-Znajek mechanism is the continuous extraction of energy from a rotating black hole via plasma currents flowing on magnetic field lines threading the horizon. In the discovery paper, Blandford and Znajek demonstrated the mechanism by solving the equations of force-free electrodynamics in a perturbative expansion valid at small black hole spin. At-tempts to extend this perturbation analysis to higher order have encountered inconsistencies.We overcome this problem using the method of matched asymptotic expansions, taking care to resolve all of the singular surfaces (light surfaces) in the problem. Working with the monopole field configuration, we show explicitly how the inconsistencies are resolved in this framework and calculate the field configuration to one order higher than previously known. However, there is no correction to the energy extraction rate at this order. These results confirm the basic consistency of the split monopole at small spin and lay a foundation for further perturbative studies of the Blandford-Znajek mechanism.
- [18] arXiv:2002.02015 [pdf, other]
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Title: On the impact of tides on the transit-timing fits to the TRAPPIST-1 systemAuthors: Emeline Bolmont, Brice-Olivier Demory, Sergi Blanco-Cuaresma, Eric Agol, Simon L. Grimm, Pierre Auclair-Desrotour, Franck Selsis, Adrien LeleuComments: 7 pages, 3 figures. Accepted for publication in Astronomy & AstrophysicsSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
Transit Timing Variations, or TTVs, can be a very efficient way of constraining masses and eccentricities of multi-planet systems. Recent measurements of the TTVs of TRAPPIST-1 led to an estimate of the masses of the planets, enabling an estimate of their densities. A recent TTV analysis using data obtained in the past two years yields a 34% and 13% increase in mass for TRAPPIST-1b and c, respectively. In most studies to date, a Newtonian N-body model is used to fit the masses of the planets, while sometimes general relativity is accounted for. Using the Posidonius N-body code, we show that in the case of the TRAPPIST-1 system, non-Newtonian effects might be also relevant to correctly model the dynamics of the system and the resulting TTVs. In particular, using standard values of the tidal Love number $k_2$ (accounting for the tidal deformation) and the fluid Love number $k_{2f}$ (accounting for the rotational flattening) leads to differences in the TTVs of TRAPPIST-1b and c similar to the differences caused by general relativity. We also show that relaxing the values of tidal Love number $k_2$ and the fluid Love number $k_{2f}$ can lead to TTVs which differ by as much as a few 10~s on a $3-4$-year timescale, which is a potentially observable level. The high values of the Love numbers needed to reach observable levels for the TTVs could be achieved for planets with a liquid ocean, which, if detected, might then be interpreted as a sign that TRAPPIST-1b and TRAPPIST-1c could have a liquid magma ocean. For TRAPPIST-1 and similar systems, the models to fit the TTVs should potentially account for general relativity, for the tidal deformation of the planets, for the rotational deformation of the planets and, to a lesser extent, for the rotational deformation of the star, which would add up to 7x2+1 = 15 additional free parameters in the case of TRAPPIST-1.
- [19] arXiv:2002.02027 [pdf, other]
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Title: Does Nature use neutral beams for interstellar plasma heating around compact objects?Comments: Submitted to MNRAS. Comments are welcome!Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
A neutral beam injection technique is employed in all major TOKAMAK facilities for heating of magnetically confined. The question then arises, whether a similar mechanism might work in astrophysical objects? For instance, a hyper-Eddington galactic binary SS433 possesses baryonic jets, moving at a quarter of the speed of light, and observations revealed signs of gas cooling and recombination on sub-pc scales and equally strong signs of powerful energy deposition on much larger scales ~100 pc. Here we consider a model where neutral atoms transport this energy. A sub-relativistic beam of neutral atoms penetrates the interstellar medium, these atoms gradually get ionised and deposit their energy over a region, whose longitudinal dimension is set by the "ionisation length". The channel, where the energy is deposited, expands sideways and drives a shock in the lateral direction. Once the density in the channel drops, the heating rate by the beam drops accordingly and the region of the energy release moves along the direction of the beam. We discuss distinct features associated with this scenario and speculate that such configuration might also boost shock acceleration of the "pick-up" protons that arise due to ionisation of neutral atoms both upstream and downstream of the shock.
- [20] arXiv:2002.02028 [pdf, ps, other]
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Title: Luminous Lyman-alpha Emitters with Very Blue UV-continuum Slopes at Redshift 5.7 <= z <= 6.6Authors: Linhua Jiang (KIAA-PKU), Seth H. Cohen, Rogier A. Windhorst, Eiichi Egami, Kristian Finlator, Daniel Schaerer, Fengwu SunComments: Published in ApJ on 2020 Feb 1; Authors' version (9 pages); See published version at this https URLJournal-ref: ApJ, 889, 90 (2020)Subjects: Astrophysics of Galaxies (astro-ph.GA)
We study six luminous Lyman-alpha emitters (LAEs) with very blue rest-frame UV continua at $5.7\le z \le 6.6$. These LAEs have previous HST and Spitzer IRAC observations. Combining our newly acquired HST images, we find that their UV-continuum slopes $\beta$ are in a range of $-3.4\le \beta \le -2.6$. Unlike previous, tentative detections of $\beta \simeq -3$ in photometrically selected, low-luminosity galaxies, our LAEs are spectroscopically confirmed and luminous ($M_{\rm UV}<-20$ mag). We model their broadband spectral energy distributions (SEDs), and find that two $\beta\simeq-2.6\pm0.2$ galaxies can be well fitted with young and dust-free stellar populations. However, it becomes increasingly difficult to fit bluer galaxies. We explore further interpretations by including non-zero LyC escape fraction $f_{\rm esc}$, very low metallicities, and/or AGN contributions. Assuming $f_{\rm esc}\simeq0.2$, we achieve the bluest slopes $\beta\simeq-2.7$ when nebular emission is considered. This can nearly explain the SEDs of two galaxies with $\beta\simeq-2.8$ and --2.9 ($\sigma_{\beta}=0.15$). Larger $f_{\rm esc}$ values and very low metallicities are not favored by the strong nebular line emission (evidenced by the IRAC flux) or the observed (IRAC 1 - IRAC 2) color. Finally, we find that the $\beta\simeq-2.9$ galaxy can potentially be well explained by the combination of a very young population with a high $f_{\rm esc}$ ($\ge0.5$) and an old, dusty population. We are not able to produce two $\beta \simeq -3.4 \pm0.4$ galaxies. Future deep spectroscopic observations are needed to fully understand these galaxies.
- [21] arXiv:2002.02029 [pdf, other]
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Title: Diffuse Lyman-alpha Halos around ~300 Spectroscopically Confirmed Lyman-alpha Emitters at z ~ 5.7Comments: Accepted for publication in ApJ (18 pages; 10 figures)Subjects: Astrophysics of Galaxies (astro-ph.GA)
We report the detection of diffuse Lyman-alpha halos (LAHs) around star-forming galaxies at $z \sim 5.7$ by stacking 310 spectroscopically confirmed Lyman-alpha (LAEs). The majority of the LAEs are identified from our spectroscopic survey of galaxies at $z>5.5$. They are all located in well-studied fields with deep narrowband and broadband imaging data. We combine the LAE sample and its subsamples in the narrowband NB816 (i.e., the Lyman-alpha band) and $z$ band (i.e., the continuum band). By comparing the stacked objects with their corresponding point spread functions, we clearly detect extended LAHs around these LAEs. We perform sophisticated simulations and analyses on statistical and systematic errors, and confirm that the detected halos are not caused by errors. The scale lengths of the LAHs, when described by a double-component model, range from 1.2 to 5.3 kpc with a typical value of $\sim$2 kpc. The LAH sizes from our sample are in agreement with those of individual LAEs at the similar redshift measured by VLT/MUSE, but are relatively smaller than those of photometrically selected LAEs in previous studies. We also find that LAEs with higher Lyman-alpha luminosities, higher UV continuum luminosities or smaller Lyman-alpha equivalent widths tend to have larger LAH sizes. Our results are consistent with a scenario that LAHs originate from the scattered light of the central galaxies by H I gas in the circumgalactic medium.
- [22] arXiv:2002.02102 [pdf, other]
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Title: Self-Interacting Dark Matter and the Origin of NGC1052-DF2 and -DF4Comments: 6 pages, 2 figuresSubjects: Astrophysics of Galaxies (astro-ph.GA)
Observations of ultra-diffuse galaxies NGC1052-DF2 and -DF4 show they contain little dark matter, challenging our understanding of galaxy formation. Using controlled N-body simulations, we explore the possibility to reproduce their properties through tidal stripping from elliptical galaxy NGC1052, in both cold dark matter (CDM) and self-interacting dark matter (SIDM) scenarios. To explain the dark matter deficiency, we find that a CDM halo must have a very low concentration so that it can lose sufficient mass in the tides. In contrast, SIDM favors a higher and more reasonable concentration as core formation enhances tidal mass loss. Stellar distributions in our SIDM benchmarks are more diffuse than CDM one, and hence the former provide a better match to the data. We further show that the presence of stellar particles is critical for preventing the halos from being totally disrupted and discuss its implications. Our results indicate that the dark matter-deficient galaxies may provide important tests for the nature of dark matter.
- [23] arXiv:2002.02104 [pdf, ps, other]
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Title: Magnetic Structure of an Erupting FilamentAuthors: Shuo Wang, Jack M. Jenkins, Valentin Martinez Pillet, Christian Beck, David M. Long, Debi Prasad Choudhary, Karin Muglach, James McAteerSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
The full 3-D vector magnetic field of a solar filament prior to eruption is presented. The filament was observed with the Facility Infrared Spectropolarimeter at the Dunn Solar Telescope in the chromospheric He i line at 10830 {\AA} on May 29 and 30, 2017. We inverted the spectropolarimetric observations with the HAnle and ZEeman Light (HAZEL) code to obtain the chromospheric magnetic field. A bimodal distribution of field strength was found in or near the filament. The average field strength was 24 Gauss, but prior to the eruption we find the 90th percentile of field strength was 435 Gauss for the observations on May 29. The field inclination was about 67 degree from the solar vertical. The field azimuth made an angle of about 47 to 65 degree to the spine axis. The results suggest an inverse configuration indicative of a flux rope topology. He i intensity threads were found to be co-aligned with the magnetic field direction. The filament had a sinistral configuration as expected for the southern hemisphere. The filament was stable on May 29, 2017 and started to rise during two observations on May 30, before erupting and causing a minor coronal mass ejection. There was no obvious change of the magnetic topology during the eruption process. Such information on the magnetic topology of erupting filaments could improve the prediction of the geoeffectiveness of solar storms.
- [24] arXiv:2002.02110 [pdf, ps, other]
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Title: Resolving the Excess of Long GRBs at low redshift in the Swift EraComments: 15 pages, 18 figures, accepted for publication in mnras (v1)Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Utilizing more than 100 long gamma-ray bursts (LGRBs) in the Swift-Ryan-2012 sample that include the observed redshifts and jet angles, Le & Mehta performed a timely study of the rate-density of LGRBs with an assumed broken power law GRB spectrum and obtained a GRB-burst-rate functional form that gives acceptable fits to the preSwift and Swift redshift and jet angle distributions. The results indicated an excess of LGRBs at redshift below $z \sim 2$ in the Swift sample. In this work, we are investigating if the excess is caused by the cosmological Hubble constant $H_0$, the $\gamma$-ray energy released $E_\gamma$, the low- and high-energy indices ($\alpha, \beta$) of the Band function, the minimum and maximum jet angles $\theta_{\rm j,min}$ and $\theta_{\rm j, max}$, or that the excess is due to a biased in the Swift-Ryan-2012 sample. Our analyses indicate that none of the above physical parameters resolved the excess problem, but suggesting that the Swift-Ryan-2012~sample is biased with possible afterglow selection effect. The following model physical parameter values provide the best fit to the Swift-Ryan-2012 and preSwift~samples: the Hubble constant $H_0 = 72 \, {\rm km s^{-1} Mpc^{-1}}$, the energy released $E_\gamma \sim 4.47 \times 10^{51}$ erg, the energy indices $\alpha \sim 0.9$ and $\beta \sim -2.13$, the jet angles of $\theta_{\rm j,max} \sim 0.8$ rad, and $\theta_{\rm j, min} \sim 0.065$ and $\sim 0.04$ rad for preSwift and Swift, respectively, $s \sim -1.55$ the jet angle power-law index, and a GRB formation rate that is similar to the Hopkins & Beacom observed star formation history and as extended by Li. Using the Swift Gamma-Ray Burst Host Galaxy Legacy Survey (SHOALS) Swift-Perley LGRB sample and applying the same physical parameter values as above, however, our model provides consistent results with this data set and indicating no excess of LGRBs at any redshift.
- [25] arXiv:2002.02130 [pdf, other]
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Title: First SETI Observations with China's Five-hundred-meter Aperture Spherical radio Telescope (FAST)Authors: Zhi-Song Zhang, Dan Werthimer, Tong-Jie Zhang, Jeff Cobb, Eric Korpela, David Anderson, Vishal Gajjar, Ryan Lee, Shi-Yu Li, Xin Pei, Xin-Xin Zhang, Shi-Jie Huang, Pei Wang, Yan Zhu, Ran Duan, Hai-Yan Zhang, Cheng-jin Jin, Li-Chun Zhu, Di LiComments: 21 pages, 19 figures, 3 tables. Accepted for publication by ApJSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
The Search for Extraterrestrial Intelligence (SETI) attempts to address the possibility of the presence of technological civilizations beyond the Earth. Benefiting from high sensitivity, large sky coverage, an innovative feed cabin for China's Five-hundred-meter Aperture Spherical radio Telescope (FAST), we performed the SETI first observations with FAST's newly commisioned 19-beam receiver; we report preliminary results in this paper. Using the data stream produced by the SERENDIP VI realtime multibeam SETI spectrometer installed at FAST, as well as its off-line data processing pipelines, we identify and remove four kinds of radio frequency interference(RFI): zone, broadband, multi-beam, and drifting, utilizing the Nebula SETI software pipeline combined with machine learning algorithms. After RFI mitigation, the Nebula pipeline identifies and ranks interesting narrow band candidate ET signals, scoring candidates by the number of times candidate signals have been seen at roughly the same sky position and same frequency, signal strength, proximity to a nearby star or object of interest, along with several other scoring criteria. We show four example candidates groups that demonstrate these RFI mitigation and candidate selection. This preliminary testing on FAST data helps to validate our SETI instrumentation techniques as well as our data processing pipeline.
- [26] arXiv:2002.02133 [pdf, other]
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Title: The frequency drift and fine structures of Solar S-bursts in the high frequency band of LOFARAuthors: PeiJin Zhang, Pietro Zucca, ChuanBing Wang, Mario M. Bisi, Bartosz Dabrowski, Richard A. Fallows, Andrzej Krankowski, Jasmina Magdalenic, Gottfried Mann, Diana E. Morosan, Christian VocksComments: 12 pagesSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (physics.space-ph)
Solar S-bursts are short duration ($<1$ s at decameter wavelengths) radio bursts that have been observed during periods of moderate solar activity, where S stands for short. The frequency drift of S-bursts can reflect the density variation and the motion state of the electron beams. In this work, we investigate the frequency drift and the fine structure of the S-bursts with the LOw Frequency ARray (LOFAR). We find that the average frequency drift rate of the S-bursts within 110-180MHz could be described by $df/dt=-0.0077f^{1.59}$. With the high time and frequency resolution of LOFAR, we can resolve the fine structures of the observed solar S-bursts. A fine drift variation pattern was found in the structure of S-bursts (referred to as solar Sb-bursts in this paper) during the type-III storm on 2019 April 13, in the frequency band of 120-240 MHz. The Sb-bursts have a quasi-periodic segmented pattern, and the relative flux intensity tends to be large when the frequency drift rate is relatively large. This kind of structure exists in about 20\% of the solar S-burst events within the observed frequency range. We propose that the fine structure is due to the density fluctuations of the background coronal density. We performed a simulation based on this theory which can reproduce the shape and relative flux intensity of the Sb-bursts. This work shows that the fine structure of solar radio bursts can be used to diagnose the coronal plasma.
- [27] arXiv:2002.02144 [pdf, other]
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Title: Protostellar disk formation by a non-rotating, non-axisymmetric collapsing cloud: model and comparison with observationsComments: Accepted for publication in Astronomy & Astrophysics. 10 pages, 11 figuresSubjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Planet-forming disks are fundamental objects thought to be inherited from large scale rotation, through the conservation of angular momentum during the collapse of a prestellar dense core. We investigate the possibility for a protostellar disk to be formed from a motionless dense core which contains non-axisymmetric density fluctuations. The rotation is thus generated locally by the asymmetry of the collapse. We study the evolution of the angular momentum in a non-axisymmetric collapse of a dense core from an analytical point of view. To test the theory, we perform three-dimensional simulations of a collapsing prestellar dense core using adaptative mesh refinement. We start from a non-axisymmetrical situation, considering a dense core with random density perturbations that follow a turbulence spectrum. We analyse the emerging disk comparing the angular momentum it contains with the one expected from our analytic development. We study the velocity gradients at different scales in the simulation as it is done with observations. We show that the angular momentum in the frame of a stellar object which is not located at the center of mass of the core is not conserved, due to inertial forces. Our simulations of such non-axisymmetrical collapse quickly produce accretion disks at the small scales in the core. The analysis of the kinematics at different scales in the simulated core reveals projected velocity gradients of amplitudes similar to the ones observed in protostellar cores, and which directions vary, sometimes even reversing when small and large scales are compared. These complex kinematics patterns appear in recent observations, and could be a discriminating feature with models where rotation is inherited from large scales. Our results from simulations without initial rotation are more consistent with these recent observations than when solid-body rotation is initially [abridged]
- [28] arXiv:2002.02150 [pdf, other]
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Title: Towards a real-time fully-coherent all-sky search for gravitational waves from compact binary coalescences using particle swarm optimizationComments: 13 pages, 12 figuresSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)
While a fully-coherent all-sky search is known to be optimal for detecting gravitational wave signals from compact binary coalescences, its high computational cost has limited current searches to less sensitive coincidence-based schemes. Following up on previous work that has demonstrated the effectiveness of Particle Swarm Optimization in reducing the computational cost of this search, we present an implementation that achieves near real-time computational speed. This is achieved by combining the search efficiency of PSO with an optimized numerical implementation of the underlying mathematical formalism and several parallelization layers in a distributed computing framework. For a network of four second-generation detectors with $60$~min data from each, the runtime of the implementation presented here ranges between $\approx 1.4$ to $\approx 0.5$ times the data duration for network signal-to-noise ratios (SNRs) of $\gtrsim 10$ and $\gtrsim 12$, respectively. The reduced runtimes are obtained with small to negligible losses in detection sensitivity: for a false alarm rate of $\simeq 1$~event per year in Gaussian stationary noise, the loss in detection probability is $\leq 5\%$ and $\leq 2\%$ for SNRs of $10$ and $12$, respectively. Using the fast implementation, we are able to quantify frequentist errors in parameter estimation for signals in the double neutron star mass range using a large number of simulated data realizations.
- [29] arXiv:2002.02155 [pdf]
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Title: The origin of s-process isotope heterogeneity in the solar protoplanetary diskComments: 25 pages, 9 figures, 1 tableJournal-ref: Nature Astronomy (2019)Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Rocky asteroids and planets display nucleosynthetic isotope variations that are attributed to the heterogeneous distribution of stardust from different stellar sources in the solar protoplanetary disk. Here we report new high precision palladium isotope data for six iron meteorite groups, which display smaller nucleosynthetic isotope variations than the more refractory neighbouring elements. Based on this observation we present a new model in which thermal destruction of interstellar medium dust results in an enrichment of s-process dominated stardust in regions closer to the Sun. We propose that stardust is depleted in volatile elements due to incomplete condensation of these elements into dust around asymptotic giant branch (AGB) stars. This led to the smaller nucleosynthetic variations for Pd reported here and the lack of such variations for more volatile elements. The smaller magnitude variations measured in heavier refractory elements suggest that material from high-metallicity AGB stars dominated stardust in the Solar System. These stars produce less heavy s-process elements compared to the bulk Solar System composition.
- [30] arXiv:2002.02166 [pdf, other]
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Title: The Bimodal Distribution in Exoplanet Radii: Considering Varying Core Compositions and $\rm H_{2}$ Envelop SizesSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Several models have been introduced in order to explain the radius distribution in exoplanet radii observed by Fulton et al. (2017) with one peak at $\rm \sim 1.3 R_{\oplus} $ the other at $\rm \sim 2.4 R_{\oplus} $ and the minimum at $\rm \sim 1.75R_{\oplus} $. In this paper we focus on the hypothesis that the exoplanet size distribution is caused by stellar XUV-induced atmospheric loss. We evolve $10^{6}$ synthetic exoplanets by exposing them to XUV irradiation from synthetic ZAMS stars. For each planet we set a different interior composition which ranged from $\rm 100 \: wt\%$ Fe (very dense) through $\rm 100 \: wt\%$ $\rm MgSiO_{3}$ (average density) and to $\rm 100 \: wt\%$ $\rm H_{2}O$ ice (low density) with varying hydrogen envelop sizes which varied from $\rm 0 \: wt\%$ (a negligible envelop) to $\rm 100 \: wt\%$ (a negligible core). Our simulations were able to replicate the bimodal distribution in exoplanet radii. We argue that in order to reproduce the distribution by Fulton et al. (2017) it is mandatory for there to be a paucity of exoplanets with masses above $\rm \sim 8M_{\oplus}$. Furthermore, our best-fit result predicts an initial flat distribution in exoplanet occurrence for $\rm M_{P} \lesssim 8M_{\oplus}$ with a strong deficiency for planets with $\rm \lesssim 3M_{\oplus}$. Our results are consistent with the $\rm \sim 1.3R_{\oplus}$ radius peak mostly encompassing denuded exoplanets whilst the $\rm \sim 2.4R_{\oplus}$ radius peak mainly comprising exoplanets with large hydrogen envelops
- [31] arXiv:2002.02186 [pdf, ps, other]
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Title: Analysing the spectral energy distributions of Galactic classical CepheidsAuthors: M.A.T. GroenewegenComments: Accepted A&ASubjects: Solar and Stellar Astrophysics (astro-ph.SR)
(abridged) Spectral energy distributions (SEDs) were constructed for a sample of 477 classical cepheids (CCs). The SEDs were fitted with a dust radiative transfer code. Four stars showed a large mid- or far-infrared excess and the fitting then included a dust component. These comprise the well-known case of RS Pup, and three stars that are (likely) Type-II cepheids (T2Cs), AU Peg, QQ Per, and FQ Lac.
The remainder of the sample was fitted with a stellar photosphere to derive the best-fitting luminosity and effective temperature. Distance and reddening were taken from the literature. The stars were plotted in a Hertzsprung-Russell diagram and compared to evolutionary tracks for cepheids and theoretical instability strips. For the large majority of stars, the position in the HRD is consistent with the instability strip for a CC or T2C. About 5% of the stars are outliers in the sense that they are much hotter or cooler than expected. A comparison to effective temperatures derived from spectroscopy suggests in some cases that the photometrically derived temperature is not correct and that this is likely linked to an incorrectly adopted reddening.
In this work the presence of a small NIR excess, as has been proposed in the literature for a few well-known cepheids, is investigated. Firstly, this was done by using a sample of about a dozen stars for which a mid-infrared spectrum is available. Secondly, the SEDs of all stars were fitted with a dust model to see if a statistically significant better fit could be obtained. The results were compared to recent work. Eight new candidates for exhibiting a NIR excess are proposed, solely based on the photometric SEDs. Obtaining mid-infrared spectra would be needed to confirm this excess. Finally, period-bolometric luminosity and period-radius relations are presented for samples of over 370 fundamental-mode CCs. - [32] arXiv:2002.02197 [pdf, ps, other]
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Title: A new orbital ephemeris for WASP-128bComments: Accepted for publication in Research Notes of the American Astronomical Society (RNAAS)Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
WASP-128 is a relatively bright (V= 12.37) G0-dwarf, known to host a transiting brown dwarf in a short-period orbit (Hod\v{z}i\'c et al. 2018 arXiv:1807.07557 (H18)). Very few such objects are known, which makes WASP-128 a prime target for further observations to better understand giant planet / brown dwarf properties,including formation and migration histories. To facilitate the planning of future observations of WASP-128b, we improve the orbital ephemeris of the system, by using the seven transits of WASP-128 observed by TESS. We note that our orbital period differs significantly from that of H18: it is more than $14\,\sigma$ (using their uncertainty) larger. This results in our ephemeris predicting a mid-2020 transit to occur almost eight hours later than the H18 ephemeris. We find, however, no evidence for any period variation.
- [33] arXiv:2002.02203 [pdf, other]
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Title: On the vortex evolution in non-isothermal protoplanetary discsComments: Accepted in MNRAS, 14 pages,8 figures, 1 tableSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
It is believed that large-scale horseshoe-like brightness asymmetries found in dozens of transitional protoplanetary discs are caused by anticyclonic vortices. These vortices can play a key role in planet formation, as mm-sized dust -- the building blocks of planets -- can be accumulated inside them. Anticyclonic vortices are formed by the Rossby wave instability, which can be excited at the gap edges opened by a giant planet or at sharp viscosity transitions of accretionally inactive regions. It is known that vortices are prone to stretching and subsequent dissolution due to disc self-gravity for canonical disc masses in the isothermal approximation. To improve the hydrodynamic model of protoplanetary discs, we include the disc thermodynamics in our model. In this paper, we present our results on the evolution of the vortices formed at the outer edge of an accretionally inactive region (dead zone) assuming an ideal equation of state and taking $PdV$ work, disc cooling in the $\beta$-approximation, and disc self-gravity into account. Thermodynamics affects the offset and the mode number (referring to the number of small vortices at the early phase) of the RWI excitation, as well as the strength, shape, and lifetime of the large-scale vortex formed through merging of the initial small vortices. We found that the inclusion of gas thermodynamics results in stronger, however decreased lifetime vortices. Our results suggest that a hypothetical vortex-aided planet formation scenario favours effectively cooling discs.
- [34] arXiv:2002.02213 [pdf, other]
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Title: A Multi-wavelength View of OJ 287 Activity in 2015-2017: Implications of Spectral Changes on Central-engine Models and MeV-GeV Emission MechanismAuthors: Pankaj Kushwaha (1,2) ((1) Department of Astronomy (IAG-USP), Sao Paulo, Brazil, (2) Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India)Comments: 12 pages, 1 figure (submitted to Galaxies)Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
A diverse range of peculiar properties across the domains of observation have made OJ 287 one of the best-explored BL Lac objects on the issues of relativistic jets and accretion physics as well as the strong theory of gravity. We here present a brief compilation of observational results from the literature and inferences/insights from the extensive studies but focus on the interpretation of its $\sim$ 12-yr QPOOs and high energy emission mechanisms. The QPOOs in one model are attributed to the disk-impact related to dynamics of the binary SMBHs while alternative models attribute it to the geometrical effect related to the precession of a single jet or double jets. We discuss implications of the new spectral features reported during the 2015--2017 multi-wavelength high activity of the source -- a break in the NIR-optical spectrum and hardening of the MeV-GeV emission accompanied by a shift in the location of its peak, in the context of the two. The reported NIR-optical break nicely fits the description of a standard accretion disk emission from an SMBH of mass $\sim~10^{10}~M_\odot$ while the time of its first appearance in end-May 2013 (MJD 56439) is in close coincidence with the time of impact predicted by the disk-impact binary SMBH model. This spectral and temporal coincidence with the model parameters of the disk-impact binary SMBH model provides independent evidence in favor of the model over the geometrical models which argue a total central-engine mass in the range of $\rm 10^{7-9}~M_\odot$. On the other hand, the MeV-GeV spectral change is naturally reproduced by the inverse Compton scattering of photons from the broad-line region and is consistent with the detection of broad emission lines during the previous cycles of quasi-periodic outbursts. Combining this with previous SED studies suggests that in OJ 287, MeV-GeV emission results from external Comptonization.
- [35] arXiv:2002.02249 [pdf, other]
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Title: A Non-Linear Magnetic Field Calibration Method for Filter-Based Magnetographs by Multilayer PerceptronAuthors: JingJing Guo, XianYong Bai, YuanYong Deng, Hui Liu, JiaBen Lin, JiangTao Su, Xiao Yang, KaiFan JiComments: 19 pages, 12 figures, 2 tables, accepted for publication in Solar PhysicsJournal-ref: Sol.Phys. 295 (2020) 5Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)
For filter-based magnetographs, the linear calibration method under the weak-field assumption is usually adopted; this leads to magnetic saturation effect in the regions with strong magnetic field. This article explores a new method to overcome the above disadvantage using a multilayer perceptron network, which we call MagMLP, based on a back-propagation algorithm with one input layer, five hidden layers, and one output layer. We use the data from the \textit{Spectropolarimeter} (SP) on board \textit{Hinode} to simulate single-wavelength observations for the model training, and take into account the influence of the Doppler velocity field and the filling factor. The training results show that the linear fitting coefficient (LFC) of the transverse field reaches above 0.91, and that of the longitudinal field is above 0.98. The generalization of the models is good because the corresponding LFCs are above 0.9 for the test subsets. Compared with the linear calibration method, the MagMLP is much more effective on dealing with the magnetic saturation effect. Analyzing an active region, the results of the linear calibration present an evident magnetic saturation effect in the umbra regions; the corresponding systematic error reaches values greater than 1000 G in most areas, or even exceeds 2000 G at some pixels. However, the results of MagMLP at these locations are very close to the inversion results, and the systematic errors are basically within 300 G. In addition, we find that there are many "bright spots" and "dark spots" on the inclination angle images from the inversion results of \textit{Hinode}/SP with values of 180 and 0 degrees, respectively, where the inversion is not reliable and does not produce a good result; the MagMLP handles these points well.
- [36] arXiv:2002.02254 [pdf, other]
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Title: Magnetorotational Instability in Diamagnetic, Misaligned Protostellar DiscsComments: 9 pages, 5 figures, published in MNRAS, 2020, vol. 491, pages 5481-5488Journal-ref: MNRAS, 491 (2020), 5481Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Plasma Physics (physics.plasm-ph)
In the present study, we addressed the question of how the growth rate of the magnetorotational instability is modified when the radial component of the stellar dipole magnetic field is taken into account in addition to the vertical component. Considering a fiducial radius in the disc where diamagnetic currents are pronounced, we carried out a linear stability analysis to obtain the growth rates of the magnetorotational instability for various parameters such as the ratio of the radial-to-vertical component and the gradient of the magnetic field, the Alfvenic Mach number and the diamagnetization parameter. Our results show that the interaction between the diamagnetic current and the radial component of the magnetic field increases the growth rate of the magnetorotational instability and generates a force perpendicular to the disc plane which may induce a torque. It is also shown that considering the radial component of the magnetic field and taking into account a radial gradient in the vertical component of the magnetic field causes an increase in the magnitudes of the growth rates of both the axisymmetric ($m=0$) and the non-axisymmetric ($m=1$) modes.
- [37] arXiv:2002.02267 [pdf, other]
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Title: Measuring black hole masses from tidal disruption events: Testing the $M_{\rm BH}-σ_*$ relationAuthors: Z.Q. Zhou (Pku), F.K. Liu (Pku, Kiaa), S. Komossa (Mpifr), R. Cao (Pku), L.C. Ho (Kiaa, Pku), Xian Chen (Pku, Kiaa), S. Li (Naoc, Pku)Comments: 39 pages, 12 figures, submitted to ApJ on 2019 December 15Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
Liu and colleagues recently proposed an elliptical accretion disk model for tidal disruption events (TDEs). They showed that the accretion disks of optical/UV TDEs are large and highly eccentric and suggested that the broad optical emission lines with complex and diverse profiles originate in the cool eccentric accretion disk of random inclination and orientation. In this paper, we calculate the radiation efficiency of the elliptical accretion disk and investigate the implications for the observations of TDEs. We compile the observational data of the peak bolometric luminosity and the total radiation energy after peak brightness of 18 TDE sources and compare the observations to the expectations from the elliptical accretion disk model. Our results show that the observations are well consistent with the expectations and that the majority of the orbital energy of the stellar debris is advected onto the black hole (BH) without being converted into radiation. By comparing the observations and the expectations, we derive the masses of the disrupted stars and BHs of the TDEs. The BH masses obtained in this paper are well consistent with those calculated with the M_BH-sigma_* relation. Our results provide an effective method to measure the masses of BHs from thousands or more of the TDEs to be discovered in the ongoing and next-generation sky surveys, no matter whether the BHs are located at the centers of the galactic nuclei or wandering in disks and halos.
- [38] arXiv:2002.02275 [pdf, other]
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Title: The Gaia-ESO Survey: detection and characterization of single line spectroscopic binariesAuthors: T. Merle, M. Van der Swaelmen, S. Van Eck, A. Jorissen, R. J. Jackson, G. Traven, T. Zwitter, D. Pourbaix, A. Klutsch, G. Sacco, R. Blomme, T. Masseron, G. Gilmore, S. Randich, C. Badenes, A. Bayo, T. Bensby, M. Bergemann, K. Biazzo, F. Damiani, D. Feuillet, A. Frasca, A. Gonneau, R. D. Jeffries, P. Jofré, L. Morbidelli, N. Mowlavi, E. Pancino, L. PrisinzanoComments: 27 pages, 24 figures, accepted for publication in A&ASubjects: Solar and Stellar Astrophysics (astro-ph.SR)
Recent and on-going large ground-based multi-object spectroscopic surveys allow to significantly increase the sample of spectroscopic binaries to get insight into their statistical properties. We investigate the repeated spectral observations of the Gaia-ESO Survey (GES) internal data release 5 to identify and characterize spectroscopic binaries with one visible component (SB1) in fields covering the discs, the bulge, the CoRot fields, and stellar clusters and associations. A statistical chi2-test is performed on spectra of the iDR5 sub-sample of approximately 43500 stars characterized by at least 2 observations and a S/N > 3. Our sample of RV variables is cleaned from contamination by pulsation/convection-induced variables using Gaia DR2 parallaxes and photometry. Monte-Carlo simulations using the SB9 catalogue of spectroscopic orbits allow to estimate our detection efficiency and to correct the SB1 rate to evaluate the GES SB1 binary fraction and its dependence with effective temperature and metallicity. We find 641 (resp., 803) FGK SB1 candidates at the 5 sigma (resp., 3 sigma) level. The orbital-period distribution is estimated from the RV standard-deviation distribution and reveals that the detected SB1 probe binaries with log(P[d]) < 4. We estimate the global GES SB1 fraction to be in the range 7-14% with a typical uncertainty of 4%. The GES SB1 frequency decreases with metallicity at a rate of -9+/-3%/dex in the metallicity range -2.7<FeH<+0.6. This anticorrelation is obtained with a confidence level higher than 93% on a homogeneous sample covering spectral types FGK and a large range of metallicities. When the present-day mass function is accounted for, this rate turns to 4+/-2%/dex with a confidence level higher than 88%. In addition we provide the variation of the SB1 fraction with metallicity separately for F, G, and K spectral types, as well as for dwarf and giant primaries.
- [39] arXiv:2002.02280 [pdf, other]
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Title: Intermittent planet migration and the formation of multiple dust rings and gaps in protoplanetary disksComments: 23 pages, 15 figures, accepted for publication in MNRASSubjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
A key challenge for protoplanetary disks and planet formation models is to be able to make a reliable connection between observed structures in the disks emission, like bright and dark rings or asymmetries, and the supposed existence of planets triggering these structures. The observation of N dark rings of emission is often interpreted as evidence for the presence of N planets which clear dust gaps around their orbit and form dust-trapping pressure maxima in the disk. The vast majority of the models that studied the impact of planets on the dynamics of dust and gas in a protoplanetary disk assumed planets on fixed orbits. Here we go a different route and examine how the large-scale inward migration of a single planet structures the dust content of a massive disk. In many circumstances, the migration of a partial gap-opening planet with a mass comparable to Saturn is found to run away intermittently. By means of 2D gas and dust hydrodynamical simulations, we show that intermittent runaway migration can form multiple dust rings and gaps across the disk. Each time migration slows down, a pressure maximum forms beyond the planet gap that traps the large dust. Post-processing of our simulations results with 3D dust radiative transfer calculations confirms that intermittent runaway migration can lead to the formation of multiple sets of bright and dark rings of continuum emission in the (sub)millimeter beyond the planet location.
- [40] arXiv:2002.02299 [pdf, other]
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Title: A stacked prism lens concept for next generation hard X-ray telescopesJournal-ref: Nature Astronomy 3 (2019) 867-872Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)
Effective collecting area, angular resolution, field of view and energy response are fundamental attributes of X-ray telescopes. The performance of state-of-the-art telescopes is currently restricted by Wolter optics, especially for hard X-rays. In this paper, we report the development of a new approach - the Stacked Prism Lens, which is lightweight, modular and has the potential for a significant improvement in effective area, while retaining high angular resolution. The proposed optics is built by stacking discs embedded with prismatic rings, created with photoresist by focused UV lithography. We demonstrate the SPL approach using a prototype lens which was manufactured and characterized at a synchrotron radiation facility. The design of a potential satellite-borne X-ray telescope is outlined and the performance is compared to contemporary missions.
- [41] arXiv:2002.02307 [pdf, other]
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Title: Determining the Co-Rotation Radii of Spiral Galaxies Using Spiral Arm Pitch Angle Measurements at Multiple WavelengthsAuthors: Shameer Abdeen (1,2), Daniel Kennefick (1,2), Julia Kennefick (1,2), Ryan Miller (3), Douglas W. Shields (1,2), Erik B. Monson (1,2), Benjamin L. Davis (4) ((1) Department of Physics, University of Arkansas, Fayetteville, USA, (2) Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, USA, (3) Department of Physics, Utica College, Utica, USA, (4) Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Australia)Comments: 9 pages, 10 figures, 4 tablesSubjects: Astrophysics of Galaxies (astro-ph.GA)
The spiral arms spanning disk galaxies are believed to be created by density waves that propagate through galactic disks. We present a novel method of finding the co-rotation radius where the spiral arm pattern speed matches the velocities of the stars within the disk. Our method uses an image-overlay technique, which involves tracing the arms of spiral galaxies on images observed in different wavelengths. Density wave theory predicts that spiral arms observed from different wavelengths show a phase crossing at the co-rotation radius. For the purpose of this study, 20 nearby galaxies were analyzed in four different wavelengths with pitch angle measurements performed by two independent methods. We used optical wavelength images ($B$-band 440nm), two infrared wavelength images provided by Spitzer (3.6$\mu$m and 8$\mu$m) and ultraviolet images from GALEX (1350\AA, 1750\AA). The results were compared and verified with other records found in the literature. We then found rotation curve data for six of our galaxies and used our co-rotation radii estimates to measure the time that would elapse between star formation and moving to their observed positions in the $B$-band spirals. The average time lapse for this motion was found to be $\sim$ 50 Myr. The success of this new method of finding the co-rotation radius confirms density wave theory in a very direct way.
- [42] arXiv:2002.02336 [pdf, other]
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Title: Detection of very-high-energy γ-ray emission from the colliding wind binary η Car with H.E.S.SAuthors: H.E.S.S. Collaboration, H. Abdalla, R. Adam, F. Aharonian, F. Ait Benkhali, E.O. Angüner, M. Arakawa, C. Arcaro, C. Armand, T. Armstrong, H. Ashkar, M. Backes, V. Barbosa Martins, M. Barnard, Y. Becherini, D. Berge, K. Bernlöhr, R. Blackwell, M. Böttcher, C. Boisson, J. Bolmont, S. Bonnefoy, J. Bregeon, M. Breuhaus, F. Brun, P. Brun, M. Bryan, M. Büchele, T. Bulik, T. Bylund, S. Caroff, A. Carosi, S. Casanova, M. Cerruti, T. Chand, S. Chandra, A. Chen, S. Colafrancesco, G. Cotter, M. Curyło, I.D. Davids, J. Davies, C. Deil, J. Devin, P. deWilt, L. Dirson, A. Djannati-Ataï, A. Dmytriiev, A. Donath, V. Doroshenko, J. Dyks, K. Egberts, F. Eichhorn, G. Emery, J.-P. Ernenwein, S. Eschbach, K. Feijen, S. Fegan, A. Fiasson, G. Fontaine, S. Funk, M. Füßling, et al. (173 additional authors not shown)Comments: 9 pages, 4 figures, 3 tables, in press with A&ASubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Aims. Colliding wind binary systems have long been suspected to be high-energy (HE; 100 MeV < E < 100 GeV) {\gamma}-ray emitters. {\eta} Car is the most prominent member of this object class and is confirmed to emit phase-locked HE {\gamma} rays from hundreds of MeV to ~100 GeV energies. This work aims to search for and characterise the very-high-energy (VHE; E >100 GeV) {\gamma}-ray emission from {\eta} Car around the last periastron passage in 2014 with the ground-based High Energy Stereoscopic System (H.E.S.S.). Methods. The region around {\eta} Car was observed with H.E.S.S. between orbital phase p = 0.78 - 1.10, with a closer sampling at p {\approx} 0.95 and p {\approx} 1.10 (assuming a period of 2023 days). Optimised hardware settings as well as adjustments to the data reduction, reconstruction, and signal selection were needed to suppress and take into account the strong, extended, and inhomogeneous night sky background (NSB) in the {\eta} Car field of view. Tailored run-wise Monte-Carlo simulations (RWS) were required to accurately treat the additional noise from NSB photons in the instrument response functions. Results. H.E.S.S. detected VHE {\gamma}-ray emission from the direction of {\eta} Car shortly before and after the minimum in the X-ray light-curve close to periastron. Using the point spread function provided by RWS, the reconstructed signal is point-like and the spectrum is best described by a power law. The overall flux and spectral index in VHE {\gamma} rays agree within statistical and systematic errors before and after periastron. The {\gamma}-ray spectrum extends up to at least ~400 GeV. This implies a maximum magnetic field in a leptonic scenario in the emission region of 0.5 Gauss. No indication for phase-locked flux variations is detected in the H.E.S.S. data.
- [43] arXiv:2002.02341 [pdf, other]
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Title: S62 on a 9.9 yr Orbit around SgrA*Comments: 18 pages, accepted and published by ApJJournal-ref: Volume 889, Number 1, Published 2020 January 24Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
We observe the S-cluster star S62 on its Keplerian orbit around the supermassive black hole in the center of our galaxy, SgrA*. The orbital time period of S62 around SgrA* is 9.9 years. We derive its mass to be around 2 M_solar which is consistent with other members of the S-cluster. From the Lucy-Richardson deconvolved images, we determine a K-band magnitude of 16.1 mag. We observe almost two complete orbits of the star with two different and independent telescopes and three different instruments. The close distance of S62 to SgrA* at its periapse of around 2 mas results in a gravitational periapse shift of almost 10%/orbit.
- [44] arXiv:2002.02401 [pdf, other]
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Title: The loss of the intra-cluster medium in globular clustersComments: 11 pages, 5 figures, accepted for publication in MNRASSubjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)
Stars in globular clusters (GCs) lose a non negligible amount of mass during their post-main sequence evolution. This material is then expected to build up a substantial intra-cluster medium (ICM) within the GC. However, the observed gas content in GCs is a couple of orders of magnitude below these expectations. Here we follow the evolution of this stellar wind material through hydrodynamical simulations to attempt to reconcile theoretical predictions with observations. We test different mechanisms proposed in the literature to clear out the gas such as ram-pressure stripping by the motion of the GC in the Galactic halo medium and ionisation by UV sources. We use the code ramses to run 3D hydrodynamical simulations to study for the first time the ICM evolution within discretised multi-mass GC models including stellar winds and full radiative transfer. We find that the inclusion of both ram-pressure and ionisation is mandatory to explain why only a very low amount of ionised gas is observed in the core of GCs. The same mechanisms operating in ancient GCs that clear the gas could also be efficient at younger ages, meaning that young GCs would not be able to retain gas and form multiple generations of stars as assumed in many models to explain "multiple populations". However, this rapid clearing of gas is consistent with observations of young massive clusters.
- [45] arXiv:2002.02420 [pdf, other]
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Title: Initial conditions for plateau inflationComments: 14 pages, 6 figuresSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
We study initial conditions for inflation in scenarios where the inflaton potential has a plateau shape. Such models are those most favored by Planck data and can be obtained in a large number of model classes. As a representative example, we consider Higgs inflation with and without an $R^2$ term in the context of Palatini gravity. We show that inflation with a large number of e-folds generically occurs in a large part of the parameter space without any fine-tuning of parameters even when the scale of inflation and the inflaton field value during inflation are much smaller than the Planck scale. We discuss consequences for detection of primordial gravitational waves and spectral tilt of curvature perturbations, as well as the recently proposed "Trans-Planckian Censorship" conjecture.
- [46] arXiv:2002.02449 [pdf, other]
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Title: The OTELO survey. II. The faint-end of the H$α$ luminosity function at z $\sim$ 0.40Authors: Marina Ramón-Pérez, Ángel Bongiovanni, Ana María Pérez García, Jordi Cepa, Maritza A. Lara-López, José Antonio de Diego, Emilio J. Alfaro Navarro, Héctor O. Castañeda, Miguel Cerviño, Mirian Fernández-Lorenzo, Jesús Gallego, J. Jesús González, J. Ignacio González-Serrano, Jakub Nadolny, Iván Oteo Gómez, Ricardo Pérez Martínez, I. Pintos-Castro, Mirjana Pović, Miguel Sánchez-PortalComments: 8 pages, 5 figures. Published in Astronomy \& AstrophysicsJournal-ref: A&A, 631A (2019), 10RSubjects: Astrophysics of Galaxies (astro-ph.GA)
We take advantage of the capability of the OTELO survey to obtain the H$\alpha$ luminosity function (LF) at ${\rm z}\sim0.40$. Because of the deepest coverage of OTELO, we are able to determine the faint end of the LF, and thus better constrain the star formation rate and the number of galaxies at low luminosities. The AGN contribution to this LF is estimated as well. We make use of the multi-wavelength catalogue of objects in the field compiled by the OTELO survey, which is unique in terms of minimum flux and equivalent width. We also take advantage of the pseudo-spectra built for each source, which allow the identification of emission lines and the discrimination of different types of objects. The H$\alpha$ luminosity function at $z\sim0.40$ is obtained, which extends the current faint end by almost 1 dex, reaching minimal luminosities of $\log_{10}L_{\rm lim}=38.5$ erg s$^{-1}$ (or $\sim0.002\, \text{M}_\odot\text{ yr}^{-1})$. The AGN contribution to the total H$\alpha$ luminosity is estimated. We find that no AGN should be expected below a luminosity of $\log_{10}L=38.6$ erg s$^{-1}$. From the sample of non-AGN (presumably, pure SFG) at $z\sim0.40$ we estimated a star formation rate density of $\rho_{\rm SFR}=0.012\pm0.005\ {\rm \text{M}_{\odot}\ yr^{-1}\ Mpc^{-3}}$.
Cross-lists for Fri, 7 Feb 20
- [47] arXiv:2001.10584 (cross-list from hep-ph) [pdf]
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Title: Two-Component Axionic Dark Matter HalosAuthors: Gennady P. Berman, Vyacheslav N. Gorshkov, Vladimir I. Tsifrinovich, Marco Merkli, Vladimir V. TereshchukSubjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics of Galaxies (astro-ph.GA); Other Condensed Matter (cond-mat.other); General Relativity and Quantum Cosmology (gr-qc)
We consider a two-component dark matter halo (DMH) of a galaxy containing ultra-light axions (ULA) of different mass. The DMH is described as a Bose-Einstein condensate (BEC) in its ground state. In the mean-field (MF) limit we have derived the integro-differential equations for the spherically symmetrical wave functions of the two DMH components. We studied numerically the radial distribution of the mass density of ULA and constructed the parameters which could be used to distinguish between the two- and one-component DMH. We also discuss an interesting connection between the BEC MF ground state of a one-component DMH and Hawking temperature and entropy of a corresponding Black Hole, and Unruh temperature.
- [48] arXiv:2002.00977 (cross-list from hep-ph) [pdf, other]
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Title: Signature of neutrino mass hierarchy in gravitational lensingComments: 20 pages, 5 figuresSubjects: High Energy Physics - Phenomenology (hep-ph); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)
In flat spacetime, the vacuum neutrino flavour oscillations are known to be sensitive only to the difference between the squared masses, and not to the individual masses, of neutrinos. In this work, we show that the lensing of neutrinos induced by a gravitational source substantially modifies this standard picture and it gives rise to a novel contribution through which the oscillation probabilities also depend on the individual neutrino masses. A gravitating mass located between a source and a detector deflects the neutrinos in their journey, and at a detection point, neutrinos arriving through different paths can lead to the phenomenon of interference. The flavour transition probabilities computed in the presence of such interference depend on the individual masses of neutrinos whenever there is a non-zero path difference between the interfering neutrinos. We demonstrate this explicitly by considering an example of weak lensing induced by a Schwarzschild mass. Through the simplest two flavour case, we show that the oscillation probability in the presence of lensing is sensitive to the sign of $\Delta m^2 = m_2^2 -m_1^2$, for non-maximal mixing between two neutrinos, unlike in the case of standard vacuum oscillation in flat spacetime. Further, the probability itself oscillates with respect to the path difference and the frequency of such oscillations depends on the absolute mass scale $m_1$ or $m_2$. We also give results for realistic three flavour case and discuss various implications of gravitationally modified neutrino oscillations and means of observing them.
- [49] arXiv:2002.01948 (cross-list from gr-qc) [pdf, ps, other]
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Title: Spontaneous scalarization of charged Reissner-Nordström black holes: Analytic treatment along the existence lineAuthors: Shahar HodComments: 7 pagesJournal-ref: Physics Letters B 798, 135025 (2019)Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
It has recently been demonstrated that charged black holes can support spatially regular matter configurations made of massless scalar fields which are non-minimally coupled to the electromagnetic field of the charged spacetime. Intriguingly, using numerical techniques, it has been revealed that the resonant spectra of the composed charged-black-hole-nonminimally-coupled-scalar-field configurations are characterized by charge-dependent discrete scalarization bands $\alpha\in\{[\alpha^{-}_{n}({\bar Q}),\alpha^{+}_{n}({\bar Q}]\}_{n=0}^{n=\infty}$, where $\alpha$ is the dimensionless coupling constant of the theory and ${\bar Q}\equiv Q/M$ is the dimensionless charge-to-mass ratio of the central supporting black hole. In the present paper we use {\it analytical} techniques in order to study the physical and mathematical properties of the spatially regular non-minimally coupled scalar field configurations (linearized scalar clouds) which are supported by the central charged Reissner-Nordstr\"om black holes. In particular, we derive a remarkably compact formula for the discrete resonant spectrum $\{\alpha^-_n({\bar Q})\}_{n=0}^{n=\infty}$ which characterizes the composed black-hole-linearized-field configurations along the {\it existence-line} of the system, the critical line which separates bare Reissner-Nordstr\"om black holes from hairy scalarized black-hole configurations. The analytical results are confirmed by direct numerical computations.
- [50] arXiv:2002.02030 (cross-list from gr-qc) [pdf, other]
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Title: Improved binary pulsar constraints on the parameterized post-Einsteinian frameworkComments: 17 pages, 9 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
The parameterized post-Einsteinian formalism was developed to search for generic deviations from general relativity with gravitational waves. We here present constraints on this framework using Bayesian analysis of a set of binary pulsar observations. In particular, we use measurements of the Keplerian and post-Keplerian parameters of six different binary pulsar systems, and Markov-Chain Monte-Carlo exploration to calculate posteriors on the parameterized post-Einsteinian parameters and derive robust constraints. We find improvements of 1-2 orders of magnitude in the strength of constraints when combining all six observations, relative to what one can achieve when using only the double binary pulsar. We also find that the constraints are robust to covariances with the binary's component masses. The bounds on the parameterized post-Einsteinian framework derived here could be used as a prior in future Bayesian tests of general relativity with gravitational wave observations.
- [51] arXiv:2002.02439 (cross-list from physics.ed-ph) [pdf, other]
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Title: Exploring Hubble Constant Data in an Introductory CourseAuthors: Jeffrey M. HydeComments: Accepted & to appear in The Physics TeacherSubjects: Physics Education (physics.ed-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Popular accounts of exciting discoveries often draw students to physics and astronomy, but at the introductory level it is challenging to connect with these in a meaningful way. The use of real astronomical data in the classroom can help bridge this gap and build valuable quantitative and scientific reasoning skills. This paper presents a strategy for studying Hubble's Law and the accelerating expansion of the universe using actual data. Along with understanding the physical concepts, an explicit goal is to develop skills for analyzing data in terms of a model.
Replacements for Fri, 7 Feb 20
- [52] arXiv:1812.06979 (replaced) [pdf, other]
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Title: Stellar ages, masses and radii from asteroseismic modeling are robust to systematic errors in spectroscopyComments: Accepted for publication in A&AJournal-ref: A&A 622, A130 (2019)Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [53] arXiv:1902.10485 (replaced) [pdf, other]
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Title: seestar: Selection functions for spectroscopic surveys of the Milky WayComments: MNRAS, revised version contains significant improvements to the model and more rigorous statistical testsSubjects: Astrophysics of Galaxies (astro-ph.GA)
- [54] arXiv:1903.03909 (replaced) [pdf, other]
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Title: Equation-of-state insensitive relations after GW170817Comments: 18 pages, 9 figures; minor adjustments and citations added; citation added; fixed Eq. (11) typo; Fixed broken referencesJournal-ref: Phys. Rev. D 99, 083016 (2019)Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
- [55] arXiv:1904.13060 (replaced) [pdf, ps, other]
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Title: On the change of old neutron star masses with galactocentric distanceComments: 30pp 2figsSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
- [56] arXiv:1905.05221 (replaced) [pdf, other]
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Title: Confirmation of Enhanced Long Wavelength Dust Emission in OMC 2/3Authors: Brian Mason, Simon Dicker, Sarah Sadavoy, Sara Stanchfield, Tony Mroczkowski, Charles Romero, Rachel Friesen, Craig Sarazin, Jonathan Sievers, Thomas Stanke, Mark DevlinComments: 19 pages, 8 figures, ApJ (in press)Subjects: Astrophysics of Galaxies (astro-ph.GA)
- [57] arXiv:1906.07750 (replaced) [pdf, other]
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Title: The Breakthrough Listen Search for Intelligent Life: Observations of 1327 Nearby Stars over 1.10-3.45 GHzAuthors: Danny C. Price, J. Emilio Enriquez, Bryan Brzycki, Steve Croft, Daniel Czech, David DeBoer, Julia DeMarines, Griffin Foster, Vishal Gajjar, Nectaria Gizani, Greg Hellbourg, Howard Isaacson, Brian Lacki, Matt Lebofsky, David H. E. MacMahon, Imke de Pater, Andrew P. V. Siemion, Dan Werthimer, James A. Green, Jane F. Kaczmarek, Ronald J. Maddalena, Stacy Mader, Jamie Drew, S. Pete WordenComments: Published 2020-02-05 (AJ)Journal-ref: The Astronomical Journal 159,3 (2020) 86Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
- [58] arXiv:1906.10218 (replaced) [pdf, other]
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Title: Cosmological constraints on post-Newtonian parameters in effectively massless scalar-tensor theories of gravityComments: 17 pages, 24 figures, 2 tables; small changes, updated references, matching published version in Phys. Rev. DJournal-ref: Phys. Rev. D 100, 103524 (2019)Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [59] arXiv:1908.04235 (replaced) [pdf, ps, other]
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Title: Effect of superfluid matter of neutron star on tidal deformabilitySubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
- [60] arXiv:1908.05890 (replaced) [pdf, ps, other]
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Title: Properties of solar Rossby waves from normal mode coupling and characterizing its systematicsComments: Added references, appendix A and errorbar in Figure 4. Accepted for publication in ApJSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [61] arXiv:1909.00815 (replaced) [pdf, ps, other]
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Title: Entropy Driven Winds: Outflows and Fountains Lifted Gently by BuoyancyComments: Replaced with final accepted MNRAS versionSubjects: Astrophysics of Galaxies (astro-ph.GA)
- [62] arXiv:1909.05804 (replaced) [pdf, other]
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Title: Black holes in the low mass gap: Implications for gravitational wave observationsComments: 7 pages, 4 figures, 1 table. v2: added a discussion on primary of GW190425 being a second generation BH in the low mass-gapSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
- [63] arXiv:1909.07984 (replaced) [pdf, other]
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Title: TOI-503: The first known brown dwarf-Am star binary from the TESS missionAuthors: Ján Šubjak (1) (2), Rishikesh Sharma (3), Theron W. Carmichael (4) (5), Marshall C. Johnson (6), Erica J. Gonzales (7), Elisabeth Matthews (8), Henri M. J. Boffin (9), Rafael Brahm (10) (41), Priyanka Chaturvedi (11), Abhijit Chakraborty (3), David R. Ciardi (12), Karen A. Collins (5), Massimiliano Esposito (11), Malcolm Fridlund (13) (14), Tianjun Gan (15), Davide Gandolfi (16), Rafael A. García (17) (42), Eike Guenther (11), Artie Hatzes (11), David W. Latham (5), Carina M. Persson (13), Howard M. Relles (5), Joshua E. Schlieder (18), Thomas Barclay (18), Courtney Dressing (19), Ian Crossfield (8), Andrew W. Howard (20), Florian Rodler (21), George Zhou (5), Samuel N. Quinn (5), Gilbert A. Esquerdo (5), Michael L. Calkins (5), Perry Berlind (5), Keivan G. Stassun (22) (43), et al. (45 additional authors not shown)Comments: 26 pages, 14 figures, 6 tables. Accepted to AJSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP)
- [64] arXiv:1909.09730 (replaced) [pdf, other]
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Title: A New Gravitational Wave Signature of Low-$T/|W|$ Instability in Rapidly Rotating Stellar Core CollapseComments: 6 pages, 5 figures, accepted for publication in MNRAS LettersSubjects: High Energy Astrophysical Phenomena (astro-ph.HE)
- [65] arXiv:1910.03898 (replaced) [pdf, other]
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Title: Observational constraints on the origin of the elements II. 3D non-LTE formation of Ba ii lines in the solar atmosphereAuthors: A. J. Gallagher, M. Bergemann, R. Collet, B. Plez, J. Leenaarts, M. Carlsson, S. A. Yakovleva, A. K BelyaevComments: Accepted for publication in A&A. 12 pages, 5 figures, 3 tables, 1 Appendix containing 4 tables. Updated to correct columns 9 & 10 in Table3, which were swapped with each otherSubjects: Solar and Stellar Astrophysics (astro-ph.SR)
- [66] arXiv:1910.09554 (replaced) [pdf, other]
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Title: Simple Yet Powerful: Hot Galactic Outflows Driven by SupernovaeComments: 9 pages, 4 figures, accepted by ApJL. Compilation of loading factors of supernovae-driven outflows is at this https URLSubjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)
- [67] arXiv:1910.09860 (replaced) [pdf, other]
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Title: Horizontal shear instabilities in rotating stellar radiation zones: I. Inflectional and inertial instabilities and the effects of thermal diffusionComments: Accepted in A&ASubjects: Solar and Stellar Astrophysics (astro-ph.SR); Atmospheric and Oceanic Physics (physics.ao-ph); Fluid Dynamics (physics.flu-dyn)
- [68] arXiv:1911.04579 (replaced) [pdf, other]
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Title: The Normalization and Slope of the Dark Matter (Sub-)Halo Mass Function on Sub-Galactic ScalesAuthors: Andrew J. Benson (1) ((1) Carnegie Institution for Science)Comments: 9 pages, MNRAS acceptedSubjects: Astrophysics of Galaxies (astro-ph.GA); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [69] arXiv:1912.01900 (replaced) [pdf, other]
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Title: A network of precision gravimeters as a detector of matter with feeble nongravitational couplingAuthors: Wenxiang Hu, Matthew Lawson, Dmitry Budker, Nataniel L. Figueroa, Derek F. Jackson Kimball, Allen P. Mills Jr., Christian VoigtSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
- [70] arXiv:1912.06703 (replaced) [pdf, other]
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Title: Constraining domain wall dark matter with a network of superconducting gravimeters and LIGOSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)
- [71] arXiv:2001.01716 (replaced) [pdf, other]
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Title: Manganese Indicates a Transition from Sub- to Near-Chandrasekhar Type Ia Supernovae in Dwarf GalaxiesAuthors: Mithi A. C. de los Reyes (1), Evan N. Kirby (1), Ivo R. Seitenzahl (2), Ken J. Shen (3) ((1) Caltech, (2) UNSW-ADFA, (3) UC Berkeley)Comments: 24 pages, 8 figures. Accepted to ApJSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
- [72] arXiv:2001.08595 (replaced) [pdf, ps, other]
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Title: Onset of turbulent fast magnetic reconnection observed in the solar atmosphereComments: Published in The Astrophysical Journal LettersJournal-ref: ApJL 890 L2 (2020)Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Plasma Physics (physics.plasm-ph); Space Physics (physics.space-ph)
- [73] arXiv:2001.09083 (replaced) [pdf, ps, other]
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Title: Orbital Dynamics of 2020 AV2: the First Vatira AsteroidAuthors: Sarah GreenstreetComments: Accepted at MNRASSubjects: Earth and Planetary Astrophysics (astro-ph.EP)
- [74] arXiv:2001.11964 (replaced) [pdf, ps, other]
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Title: Cosmographic analysis of redshift driftAuthors: Francisco S. N. Lobo (Universidade de Lisboa), Jose Pedro Mimoso (Universidade de Lisboa), Matt Visser (Victoria University of Wellington)Comments: V1: 24 pages. V2: 25 pages, 2 references added, no physics changesSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
- [75] arXiv:2002.00954 (replaced) [pdf, other]
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Title: Polarization Imaging of M87 Jets by General Relativistic Radiative Transfer Calculation based on GRMHD SimulationsComments: Final version. 18 pages, 14 figures, 1 table. Accepted by PASJSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)
- [76] arXiv:2002.01494 (replaced) [pdf]
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Title: Magnitude to luminance conversions and visual brightness of the night skyComments: Version accepted for publication in Monthly Notices of the Royal Astronomical Society (2020). 5 figures, 1 table, 17 pages. Some misprints corrected in the web abstractSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)
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