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The Astrophysical Journal (ApJ)

Resumen/Descripción – provisto por la editorial en inglés
The Astrophysical Journal is an open access journal devoted to recent developments, discoveries, and theories in astronomy and astrophysics. Publications in ApJ constitute significant new research that is directly relevant to astrophysical applications, whether based on observational results or on theoretical insights or modeling.
Palabras clave – provistas por la editorial

astronomy; astrophysics

Disponibilidad
Institución detectada Período Navegá Descargá Solicitá
No detectada desde jul. 1995 / hasta dic. 2023 IOPScience

Información

Tipo de recurso:

revistas

ISSN impreso

0004-637X

ISSN electrónico

1538-4357

Editor responsable

American Astronomical Society (AAS)

Idiomas de la publicación

  • inglés

País de edición

Reino Unido

Información sobre licencias CC

https://creativecommons.org/licenses/by/4.0/

Cobertura temática

Tabla de contenidos

New Variable Hot Subdwarf Stars Identified from Anomalous Gaia Flux Errors, Observed by TESS, and Classified via Fourier Diagnostics

Brad N. BarlowORCID; Kyle A. CorcoranORCID; Isabelle M. ParkerORCID; Thomas KupferORCID; Péter NémethORCID; J. J. HermesORCID; Isaac D. LopezORCID; Will J. FrondorfORCID; David VestalORCID; Jazzmyn HoldenORCID

<jats:title>Abstract</jats:title> <jats:p>Hot subdwarf stars are mostly stripped red giants that can exhibit photometric variations due to stellar pulsations, eclipses, the reflection effect, ellipsoidal modulation, and Doppler beaming. Detailed studies of their light curves help constrain stellar parameters through asteroseismological analyses or binary light-curve modeling and generally improve our capacity to draw a statistically meaningful picture of this enigmatic stage of stellar evolution. From an analysis of Gaia DR2 flux errors, we have identified around 1200 candidate hot subdwarfs with inflated flux errors for their magnitudes—a strong indicator of photometric variability. As a pilot study, we obtained 2 minute cadence TESS Cycle 2 observations of 187 candidate hot subdwarfs with anomalous Gaia flux errors. More than 90% of our targets show significant photometric variations in their TESS light curves. Many of the new systems found are cataclysmic variables, but we report the discovery of several new variable hot subdwarfs, including HW Vir binaries, reflection-effect systems, pulsating sdBV<jats:sub> <jats:italic>s</jats:italic> </jats:sub> stars, and ellipsoidally modulated systems. We determine atmospheric parameters for select systems using follow-up spectroscopy from the 3 m Shane telescope. Finally, we present a Fourier diagnostic plot for classifying binary light curves using the relative amplitudes and phases of their fundamental and harmonic signals in their periodograms. This plot makes it possible to identify certain types of variables efficiently, without directly investigating their light curves, and may assist in the rapid classification of systems observed in large photometric surveys.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 20

The Variation of the Gas Content of Galaxy Groups and Pairs Compared to Isolated Galaxies

Sambit RoychowdhuryORCID; Martin J. MeyerORCID; Jonghwan RheeORCID; Martin A. ZwaanORCID; Garima ChauhanORCID; Luke J. M. DaviesORCID; Sabine BellstedtORCID; Simon P. DriverORCID; Claudia del P. LagosORCID; Aaron S. G. RobothamORCID; Joss Bland-HawthornORCID; Richard DodsonORCID; Benne W. HolwerdaORCID; Andrew M. HopkinsORCID; Maritza A. Lara-LópezORCID; Ángel R. López-SánchezORCID; Danail ObreschkowORCID; Kristof RozgonyiORCID; Matthew T. WhitingORCID; Angus H. WrightORCID

<jats:title>Abstract</jats:title> <jats:p>We measure how the atomic gas (H <jats:sc>i</jats:sc>) fraction <jats:inline-formula> <jats:tex-math> <?CDATA $\left({f}_{{\rm{H}}\,{\rm\small{I}}}=\tfrac{{M}_{{\rm{H}}\,{\rm\small{I}}}}{{M}_{* }}\right)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mspace width="0.25em" /> <mml:mi mathsize="small" mathvariant="normal">I</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mstyle displaystyle="false"> <mml:mfrac> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mspace width="0.25em" /> <mml:mi mathsize="small" mathvariant="normal">I</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> </mml:mrow> </mml:mfrac> </mml:mstyle> </mml:mrow> </mml:mfenced> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac49eaieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of groups and pairs taken as single units vary with average stellar mass (〈<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>〉) and average star formation rate (〈SFR〉), compared to isolated galaxies. The H <jats:sc>i</jats:sc> 21 cm emission observation are from (i) archival ALFALFA survey data covering three fields from the GAMA survey (provides environmental and galaxy properties), and (ii) DINGO pilot survey data of one of those fields. The mean <jats:italic>f</jats:italic> <jats:sub>H <jats:sc>i</jats:sc> </jats:sub> for different units (groups/pairs/isolated galaxies) are measured in regions of the log(〈<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>〉)–log(〈SFR〉) plane, relative to the <jats:italic>z</jats:italic> ∼ 0 star-forming main sequence (SFMS) of individual galaxies, by stacking <jats:italic>f</jats:italic> <jats:sub>H <jats:sc>i</jats:sc> </jats:sub> spectra of individual units. For ALFALFA, <jats:italic>f</jats:italic> <jats:sub>H <jats:sc>i</jats:sc> </jats:sub> spectra of units are measured by extracting H <jats:sc>i</jats:sc> spectra over the full groups/pair areas and dividing by the total stellar mass of member galaxies. For DINGO, <jats:italic>f</jats:italic> <jats:sub>H <jats:sc>i</jats:sc> </jats:sub> spectra of units are measured by co-adding H <jats:sc>i</jats:sc> spectra of individual member galaxies, followed by division by their total stellar mass. For all units, the mean <jats:italic>f</jats:italic> <jats:sub>H <jats:sc>i</jats:sc> </jats:sub> decreases as we move to higher 〈<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>〉 along the SFMS and as we move from above the SFMS to below it at any 〈<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>〉. From the DINGO-based study, mean <jats:italic>f</jats:italic> <jats:sub>H <jats:sc>i</jats:sc> </jats:sub> in groups appears to be lower compared to isolated galaxies for all 〈<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>〉 along the SFMS. From the ALFALFA-based study, we find substantially higher mean <jats:italic>f</jats:italic> <jats:sub>H <jats:sc>i</jats:sc> </jats:sub> in groups compared to isolated galaxies (values for pairs being intermediate) for 〈<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>〉 ≲ 10<jats:sup>9.5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, indicating the presence of substantial amounts of H <jats:sc>i</jats:sc> not associated with cataloged member galaxies in low mass groups.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 20

Prospects for Measuring Off-axis Spins of Binary Black Holes with Plus-era Gravitational-wave Detectors

Alan M. KneeORCID; Jess McIverORCID; Miriam CaberoORCID

<jats:title>Abstract</jats:title> <jats:p>The mass and spin properties of binary black holes (BBHs) inferred from their gravitational-wave signatures reveal important clues about how these systems form. BBHs originating from isolated binary evolution are expected to have spins preferentially aligned with their orbital angular momentum, whereas there is no such preference in binaries formed via dynamical assembly. The fidelity with which near-future gravitational-wave detectors can measure off-axis spins will have implications for the study of BBH formation channels. In this work, we examine the degree to which the Advanced LIGO Plus (A+) and Advanced Virgo Plus (AdV+) interferometric detectors can measure both aligned and misaligned spins. We compare spin resolution between the LIGO-Virgo network operating at either A+/AdV+ (“Plus”) sensitivity or Advanced-era design (“Design”) sensitivity using simulated BBH gravitational-wave signals injected into synthetic detector noise. The signals are distributed over the mass-spin parameter space of likely BBH systems, accounting for the effects of precession and higher-order modes. We find that the Plus upgrades yield significant improvements in spin estimation for systems with unequal masses and moderate or large spins. Using simulated signals modeled after different types of hierarchical BBH mergers, we also conclude that the Plus detector network will yield substantially improved spin estimates for 1G+2G binaries compared to the Design network.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 21

ALMA 200 pc Imaging of a z ∼ 7 Quasar Reveals a Compact, Disk-like Host Galaxy

Fabian WalterORCID; Marcel NeelemanORCID; Roberto DecarliORCID; Bram VenemansORCID; Romain MeyerORCID; Axel WeissORCID; Eduardo BañadosORCID; Sarah E. I. BosmanORCID; Chris CarilliORCID; Xiaohui FanORCID; Dominik RiechersORCID; Hans–Walter RixORCID; Todd A. ThompsonORCID

<jats:title>Abstract</jats:title> <jats:p>We present 0.″035 resolution (∼200 pc) imaging of the 158 <jats:italic>μ</jats:italic>m [C <jats:sc>ii</jats:sc>] line and the underlying dust continuum of the <jats:italic>z</jats:italic> = 6.9 quasar J234833.34–305410.0. The 18 hour Atacama Large Millimeter/submillimeter Array observations reveal extremely compact emission (diameter ∼1 kpc) that is consistent with a simple, almost face-on, rotation–supported disk with a significant velocity dispersion of ∼160 km s<jats:sup>−1</jats:sup>. The gas mass in just the central 200 pc is ∼4 × 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, about a factor of two higher than that of the central supermassive black hole. Consequently we do not resolve the black hole’s sphere of influence, and find no kinematic signature of the central supermassive black hole. Kinematic modeling of the [C <jats:sc>ii</jats:sc>] line shows that the dynamical mass at large radii is consistent with the gas mass, leaving little room for a significant mass contribution by stars and/or dark matter. The Toomre–Q parameter is less than unity throughout the disk, and thus is conducive to star formation, consistent with the high-infrared luminosity of the system. The dust in the central region is optically thick, at a temperature &gt;132 K. Using standard scaling relations of dust heating by star formation, this implies an unprecedented high star formation rate density of &gt;10<jats:sup>4</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup> kpc<jats:sup>−2</jats:sup>. Such a high number can still be explained with the Eddington limit for star formation under certain assumptions, but could also imply that the central supermassive black hole contributes to the heating of the dust in the central 200 pc.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 21

Cosmic-Ray Transport near the Sun

R. D. StraussORCID; J. P. van den BergORCID; J. S RankinORCID

<jats:title>Abstract</jats:title> <jats:p>The strongly diverging magnetic field lines in the very inner heliosphere, through the associated magnetic focusing/mirroring forces, can, potentially, lead to highly anisotropic galactic cosmic-ray distributions close to the Sun. Using a simplified analytical approach, validated by numerical simulations, we study the behavior of the galactic cosmic-ray distribution in this newly explored region of the heliosphere and find that significant anisotropies can be expected inside 0.2 au.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 22

Tidal Erasure of Stellar Obliquities Constrains the Timing of Hot Jupiter Formation

Christopher SpaldingORCID; Joshua N. WinnORCID

<jats:title>Abstract</jats:title> <jats:p>Stars with hot Jupiters sometimes have high obliquities, which are possible relics of hot Jupiter formation. Based on the characteristics of systems with and without high obliquities, it is suspected that obliquities are tidally damped when the star has a thick convective envelope, as is the case for main-sequence stars cooler than ∼6100 K, and the orbit is within ∼8 stellar radii. A promising theory for tidal obliquity damping is the dissipation of inertial waves within the star’s convective envelope. Here, we consider the implications of this theory for the timing of hot Jupiter formation. Specifically, hot stars that currently lack a convective envelope possess one during their pre-main sequence. We find that hot Jupiters orbiting within a critical distance of ∼0.02 au from a misaligned main-sequence star lacking a thick convective envelope must have acquired their tight orbits after a few tens of millions of years in order to have retained their obliquities throughout the pre-main sequence. There are four known systems for which this argument applies–XO-3b, Corot-3b, WASP-14b, and WASP-121b–subject to uncertainties surrounding inertial wave dissipation. Moreover, we conclude that a recently identified overabundance of near-polar hot Jupiters is unlikely sculpted by tides, instead reflecting their primordial configuration. Finally, hot Jupiters arriving around cool stars after a few hundreds of millions of years likely find the host star rotating too slowly for efficient obliquity damping. We predict that the critical effective temperature separating aligned and misaligned stars should vary with metallicity, from 6300 to 6000 K as [Fe/H] varies from −0.3 to +0.3.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 22

Stellar Abundance Maps of the Milky Way Disk

Anna-Christina EilersORCID; David W. HoggORCID; Hans-Walter RixORCID; Melissa K. NessORCID; Adrian M. Price-WhelanORCID; Szabolcs MészárosORCID; Christian NitschelmORCID

<jats:title>Abstract</jats:title> <jats:p>To understand the formation of the Milky Way’s prominent bar it is important to know whether stars in the bar differ in the chemical element composition of their birth material as compared to disk stars. This requires stellar abundance measurements for large samples across the Milky Way’s body. Such samples, e.g., luminous red giant stars observed by the Sloan Digital Sky Survey’s APOGEE survey, will inevitably span a range of stellar parameters; as a consequence, both modeling imperfections and stellar evolution may preclude consistent and precise estimates of their chemical composition at a level of purported bar signatures, which has left current analyses of a chemically distinct bar inconclusive. Here, we develop a new self-calibration approach to eliminate both modeling and astrophysical abundance systematics among red giant branch (RGB) stars of different luminosities (and hence surface gravity <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}g$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac54adieqn1.gif" xlink:type="simple" /> </jats:inline-formula>). We apply our method to 48,853 luminous APOGEE Data Release 16 RGB stars to construct spatial abundance maps of 20 chemical elements near the Milky Way’s mid-plane, covering galactocentric radii of 0 kpc &lt; <jats:italic>R</jats:italic> <jats:sub>GC</jats:sub> &lt; 20 kpc. Our results indicate that there are no abundance variations whose geometry matches that of the bar, and that the mean abundance gradients vary smoothly and monotonically with galactocentric radius. We confirm that the high-<jats:italic>α</jats:italic> disk is chemically homogeneous, without spatial gradients. Furthermore, we present the most precise [Fe/H] versus <jats:italic>R</jats:italic> <jats:sub>GC</jats:sub> gradient to date with a slope of − 0.057 ±0.001 dex kpc<jats:sup>−1</jats:sup> out to approximately 15 kpc.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 23

Toward a More Complete Optical Census of Active Galactic Nuclei via Spatially Resolved Spectroscopy

Julia M. Comerford; James NegusORCID; R. Scott BarrowsORCID; Dominika WylezalekORCID; Jenny E. GreeneORCID; Francisco Müller-Sánchez; Rebecca Nevin

<jats:title>Abstract</jats:title> <jats:p>While emission line flux ratio diagnostics are the most common technique for identifying active galactic nuclei (AGNs) in optical spectra, applying this approach to single-fiber spectra of galaxies can omit entire subpopulations of AGNs. Here, we use spatially resolved spectroscopy from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to construct a sample of 10 galaxies where Baldwin–Philips–Terlevich line flux ratio diagnostics classify each galaxy’s central 3″ spectrum as LINER or star-forming, while &gt;10% of the spaxels in the galaxy’s MaNGA footprint are classified as Seyfert. We obtain Chandra observations of these 10 galaxies with off-nuclear Seyfert regions to determine whether AGNs are actually present in them. Our main result is that 7–10 (depending on strictness of criteria) of the galaxies host one or more X-ray AGNs, even though none of them were classified as AGNs based on their single-fiber optical spectra. We find that these AGNs were not identified in the single-fiber spectra because they are AGNs in the nuclei of companion galaxies, low-luminosity AGNs, dust-obscured AGNs, and/or flickering AGNs. In summary, we find that off-nuclear AGN signatures may increase the number of known AGNs by a factor of two over what conventional single nuclear fiber spectra identify. Our results show that spatially resolved spectroscopy can be leveraged to reveal a more complete census of AGNs that are traditionally missed by single-fiber spectra.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 23

Numerical Solutions of the External Field Effect on the Radial Acceleration in Disk Galaxies

Kyu-Hyun ChaeORCID; Mordehai Milgrom

<jats:title>Abstract</jats:title> <jats:p>In modified Newtonian dynamics (MOND)-based theories, the strong equivalence principle is generically broken in an idiosyncratic manner, manifested in the action of an “external field effect” (EFE). The internal dynamics in a self-gravitating system is affected even by a constant external field. In disk galaxies, the EFE can induce warps and modify the rotational speeds. Due to the nonlinearity of MOND, it is difficult to derive analytic expressions of this important effect in a disk. Here we study numerically the EFE in two nonrelativistic Lagrangian theories of MOND: the “Aquadratic–Lagrangian” theory (AQUAL) and “Quasilinear MOND” (QUMOND). For AQUAL, we consider only the axisymmetric field configurations with the external field along the disk axis, or a spherical galaxy with test-particle orbits inclined to the external field. For the more manageable QUMOND, we also calculate the three-dimensional field configurations, with the external field inclined to the disk axis. We investigate in particular to what degree an external field modifies the quasi-flat part of rotation curves. While our QUMOND results agree well with published numerical results in QUMOND, we find that AQUAL predicts weaker EFE than published AQUAL results. However, AQUAL still predicts stronger EFE than QUMOND, which demonstrates current theoretical uncertainties. We also illustrate how the MOND prediction on the rising part of the rotation curve, in the inner parts, depends largely on disk thickness but only weakly on a plausible external field for a fixed galaxy model. Finally, we summarize our results for the outer parts as an improved, approximate analytic expression.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 24

New Tests of Milli-lensing in the Blazar PKS 1413 + 135

A. L. PeirsonORCID; I. Liodakis; A. C. S ReadheadORCID; M. L. ListerORCID; E. S. PerlmanORCID; M. F. AllerORCID; R. D. BlandfordORCID; K. J. B. GraingeORCID; D. A. GreenORCID; M. A. GurwellORCID; M. W. Hodges; T. HovattaORCID; S. KiehlmannORCID; A. LähteenmäkiORCID; W. Max-MoerbeckORCID; T. McalooneORCID; S. O’Neill; V. Pavlidou; T. J. PearsonORCID; V. RaviORCID; R. A. Reeves; P. F. ScottORCID; G. B. TaylorORCID; D. J. TitteringtonORCID; M. TornikoskiORCID; H. K. VedanthamORCID; P. N. Wilkinson; D. T. Williams; J. A. ZensusORCID

<jats:title>Abstract</jats:title> <jats:p>Symmetric achromatic variability (SAV) is a rare form of radio variability in blazars that has been attributed to gravitational milli-lensing by a ∼10<jats:sup>2</jats:sup>–10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> mass condensate. Four SAVs have been identified between 1980 and 2020 in the long-term radio monitoring data of the blazar PKS 1413 + 135. We show that all four can be fitted with the same, unchanging, gravitational lens model. If SAV is due to gravitational milli-lensing, PKS 1413 + 135 provides a unique system for studying active galactic nuclei with unprecedented microarcsecond resolution, as well as for studying the nature of the milli-lens itself. We discuss two possible candidates for the putative milli-lens: a giant molecular cloud hosted in the intervening edge-on spiral galaxy, and an undetected dwarf galaxy with a massive black hole. We find a significant dependence of SAV crossing time on frequency, which could indicate a fast shock moving in a slower underlying flow. We also find tentative evidence for a 989 day periodicity in the SAVs, which, if real, makes possible the prediction of future SAVs: the next three windows for possible SAVs begin in 2022 August, 2025 May, and 2028 February.</jats:p>

Palabras clave: Space and Planetary Science; Astronomy and Astrophysics.

Pp. 24