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|---|---|---|---|---|
2022ApJS..260...28P
|
New Fe I Level Energies and Line Identifications from Stellar Spectra. III. Initial Results from UV, Optical, and Infrared Spectra
|
The spectrum of neutral iron is critical to astrophysics, yet furnace laboratory experiments cannot reach high-lying Fe I levels. Instead, Peterson & Kurucz and Peterson et al. adopted ultraviolet (UV) and optical spectra of warm stars to identify and assign energies for 124 Fe I levels with 1900 detectable Fe I lines, and to derive astrophysical gf values for over 1000 of these. An energy value was assumed for each unknown Fe I level, and confirmed if the wavelengths predicted in updated Kurucz Fe I calculations matched the wavelengths of four or more unidentified lines in the observed spectra. Nearly all these identifications were for LS levels, those characterized by spin-orbit coupling, whose lines fall primarily at UV and optical wavelengths. This work contributes nearly 100 new Fe I level identifications. Thirty-nine LS levels are identified largely by incorporating published positions of unidentified laboratory Fe I lines with wavelengths <2000 Å. Adding infrared (IR) spectra provided 60 Fe I jK levels, where a single outer electron orbits a compact core. Their weak IR lines are searchable, because their mutual energies obey tight relationships. For each new Fe I level, this work again makes publicly available its identification, its energy, and a list of its potentially detectable lines with theoretical gf values, totalling >16,000 lines. For over 2000 of these, this work provides astrophysical gf values adjusted semiempirically to fit the stellar spectra. The potential impact of this work on modeling UV and IR stellar spectra is noted.
|
[
2064,
2073,
2074,
2078,
2085,
1577,
1581,
1590
] |
[
"atomic data benchmarking",
"spectral line identification",
"transition probabilities",
"experimental techniques",
"line positions",
"stellar abundances",
"stellar ages",
"stellar colors"
] |
2020ApJ...894..110P
|
Thermal Formation of Ammonium Carbamate on the Surface of Laboratory Analogs of Carbonaceous Grains in Protostellar Envelopes and Planet-forming Disks
|
The catalytic role of dust grain surfaces in the thermal reaction CO<SUB>2</SUB> + 2NH<SUB>3</SUB> → NH<SUB>4</SUB><SUP>+</SUP>NH<SUB>2</SUB>COO<SUP>-</SUP> was recently demonstrated by our group. The rate coefficients for the reaction at 80 K on the surface of nanometer-sized carbon and silicate grains were measured to be up to three times higher compared to the reaction rate coefficients measured on KBr. In this study, the reaction was performed on carbon grains and on KBr in the extended temperature range of 50-80 K and with the addition of water ice. The reaction activation energy was found to be about three times lower on grains compared to the corresponding ice layer on KBr. Thus, the catalytic role of the dust grain surface in the studied reaction can be related to a reduction of the reaction barrier. Addition of water to NH<SUB>3</SUB>:CO<SUB>2</SUB> ice on grains slowed the reaction down. At the H<SUB>2</SUB>O:CO<SUB>2</SUB> ratio of 5:1, the reaction was not detected on the experimental timescale. This result calls into question the thermal formation of ammonium carbamate in dense molecular clouds and outer regions of protostellar and protoplanetary environments with dominating water ice mantle chemistry. However, it can still happen in inner regions of protostellar and protoplanetary environments in crystalline ices.
|
[
836,
201,
75,
2080,
2081,
2004,
2090
] |
[
"interstellar dust",
"carbonaceous grains",
"astrochemistry",
"reaction catalysts",
"reaction rates",
"laboratory astrophysics",
"solid matter physics"
] |
2022ApJS..262....6F
|
The Velocity Map Asymmetry of Ionized Gas in MaNGA. I. The Catalog and General Properties
|
The SDSS-IV MaNGA survey has measured two-dimensional maps of emission-line velocities for a statistically powerful sample of nearby galaxies. The asymmetric features of these kinematics maps reflect the nonrotational component of a galaxy's internal motion of ionized gas. In this study, we present a catalog of kinematic asymmetry measurements of the Hα velocity map of a sample of 5353 MaNGA galaxies. Based on this catalog, we find that "special" galaxies (e.g., merging galaxies, barred galaxies, and active galactic nucleus host galaxies) contain more galaxies with highly asymmetric velocity maps. However, we notice that more than half of galaxies with high kinematic asymmetry in our sample are quite "regular." For those "regular" galaxies, kinematic asymmetry shows a significant anticorrelation with stellar mass at $\mathrm{log}{M}_{\star }\lt 9.7$ , while such a trend becomes very weak at $\mathrm{log}{M}_{\star }\gt 9.7$ . Moreover, at a given stellar mass, the kinematic asymmetry shows weak correlations with photometric morphology, star formation rate, and environment, while it is independent of H I gas content. We also have quantified the observational effects in the kinematic asymmetry measurement. We find that both the signal-to-noise ratio of Hα flux and disk inclination angle contribute to the measures of kinematic asymmetry, while the physical spatial resolution is an irrelevant factor inside the MaNGA redshift coverage.
|
[
573,
602,
595,
622
] |
[
"galaxies",
"galaxy kinematics",
"galaxy formation",
"galaxy structure"
] |
2021ApJ...921L..34M
|
CI Tau: A Controlled Experiment in Disk-Planet Interaction
|
CI Tau is a young (~2 Myr) T Tauri system with a substantial near-infrared (NIR) excess in its spectral energy distribution (SED), indicating that the protoplanetary disk extends very close to its star. This is seemingly at odds with the radial-velocity discovery of CI Tau b, a ~12 M<SUB>J</SUB> planet at ~0.1 au, which would be expected to carve a wide, deep cavity in the innermost disk. To investigate this apparent contradiction, we run 2D hydrodynamics simulations to study the effect of the planet on the disk, then post-process the results with radiative transfer to obtain an SED. We find that at ~0.1 au, even such a massive companion has little impact on the NIR excess, a result that holds regardless of planetary eccentricity and dust size distribution. Conversely, the observed full-disk signature in CI Tau's SED is consistent with the existence of the hot super-Jupiter CI Tau b. As our simulations uncover, clear transition-disk signatures in SEDs are more likely to be signposts of nascent "warm" Jupiters, located at around 1 au in the future habitable zones of their host stars.
|
[
1300,
489,
1335,
1963
] |
[
"protoplanetary disks",
"exoplanet detection methods",
"radiative transfer",
"hydrodynamics"
] |
2020ApJ...904..187W
|
Lifting the Veil on Quark Matter in Compact Stars with Core g-mode Oscillations
|
Compact stars containing quark matter may masquerade as neutron stars in the range of measured mass and radius, making it difficult to draw firm conclusions on the phase of matter inside the star. The sensitivity of core g-mode oscillations to the presence of a mixed phase may alleviate this difficulty. In hybrid stars that admit quark matter in a mixed phase, the g-mode frequency rises sharply due to a marked decrease in the equilibrium sound speed. Resonant excitation of g-modes can leave an imprint in the waveform of coalescing binary compact stars. We present analytic and numeric results to assess the sensitivity displayed by g-mode oscillations to quark matter in a homogeneous or mixed phase and also compute relevant damping times in quark matter due to viscosity.
|
[
1108,
678,
1617
] |
[
"neutron stars",
"gravitational waves",
"stellar oscillations"
] |
2021ApJ...922...14P
|
Nuclear Physics Multimessenger Astrophysics Constraints on the Neutron Star Equation of State: Adding NICER's PSR J0740+6620 Measurement
|
In the past few years, new observations of neutron stars (NSs) and NS mergers have provided a wealth of data that allow one to constrain the equation of state (EOS) of nuclear matter at densities above nuclear saturation density. However, most observations were based on NSs with masses of about 1.4 M<SUB>⊙</SUB>, probing densities up to ~three to four times the nuclear saturation density. Even higher densities are probed inside massive NSs such as PSR J0740+6620. Very recently, new radio observations provided an update to the mass estimate for PSR J0740+6620, and X-ray observations by the NICER and XMM telescopes constrained its radius. Based on these new measurements, we revisit our previous nuclear physics multimessenger astrophysics constraints and derive updated constraints on the EOS describing the NS interior. By combining astrophysical observations of two radio pulsars, two NICER measurements, the two gravitational-wave detections GW170817 and GW190425, detailed modeling of the kilonova AT 2017gfo, and the gamma-ray burst GRB 170817A, we are able to estimate the radius of a typical 1.4 M<SUB>⊙</SUB> NS to be ${11.94}_{-0.87}^{+0.76}\,\mathrm{km}$ at 90% confidence. Our analysis allows us to revisit the upper bound on the maximum mass of NSs and disfavors the presence of a strong first-order phase transition from nuclear matter to exotic forms of matter, such as quark matter, inside NSs.
|
[
2077,
1108,
1107,
678
] |
[
"nuclear physics",
"neutron stars",
"neutron star cores",
"gravitational waves"
] |
2023ApJ...957L..19S
|
VERTICO and IllustrisTNG: The Spatially Resolved Effects of Environment on Galactic Gas
|
It has been shown in previous publications that the TNG100 simulation quantitatively reproduces the observed reduction in each of the total atomic and total molecular hydrogen gas for galaxies within massive halos, i.e., dense environments. In this Letter, we study how well TNG50 reproduces the resolved effects of a Virgo-like cluster environment on the gas surface densities of satellite galaxies with m <SUB>*</SUB> > 10<SUP>9</SUP> M <SUB>⊙</SUB> and star formation rate > 0.05 M <SUB>⊙</SUB> yr<SUP>-1</SUP>. We select galaxies in the simulation that are analogous to those in the HERACLES and VERTICO surveys and mock-observe them to the common specifications of the data. Although TNG50 does not quantitatively match the observed gas surface densities in the centers of galaxies, the simulation does qualitatively reproduce the trends of gas truncation and central density suppression seen in VERTICO in both H I and H<SUB>2</SUB>. This result promises that modern cosmological hydrodynamic simulations can be used to reliably model the post-infall histories of cluster satellite galaxies.
|
[
2029,
594,
833,
849
] |
[
"galaxy environments",
"galaxy evolution",
"interstellar atomic gas",
"interstellar molecules"
] |
2022AJ....164..259Y
|
Tentative Evidence for Transit-timing Variations of WASP-161b
|
We report on the detection of transit-timing variations (TTV) of WASP-161b by using the combination of Transiting Exoplanet Survey Satellite (TESS) data and archival data. The midpoint of the transits in TESS data are offset by ~67 minutes in 2019 January, and ~203 minutes in 2021 January, based on the ephemeris published in previous work. We are able to reproduce the transit timings from the archival light curve (SSO-Europa; 2018 January) and find that the timing is consistent with the published ephemeris under a constant period assumption. Conversely, we find that the transit midpoint of the SSO-Europa light curve indicates a 6.97 minutes variation at 4.63σ compared to the prediction obtained from TESS timings, and a constant orbit period assumption. The TTVs could be modeled with a quadratic function, yielding a constant period change. The period derivative $\dot{P}$ is -1.16 × 10<SUP>-7</SUP> ± 2.25 × 10<SUP>-8</SUP> days per day (or -3.65 s yr<SUP>-1</SUP>), using timings obtained from SSO-Europa and TESS light curves. Different scenarios, including a decaying period and apsidal precession, can potentially explain these TTVs but they both introduce certain inconsistencies.
|
[
484,
486,
1710,
1709
] |
[
"exoplanet systems",
"exoplanet astronomy",
"transit timing variation method",
"transit photometry"
] |
2024PASP..136f4503Z
|
Identification of Radio Frequency Interference Using Multi-scale TransUNet
|
Radio observation is a method for conducting astronomical observations using radio waves. A common challenge in radio observations is Radio Frequency Interference (RFI), which refers to the unintentional or intentional interference of radio signals from other wireless sources within the radio frequency band. Such interference contaminates the astronomical signals received by radio telescopes, significantly affecting time–frequency domain astronomical observations and research. Consequently, identifying RFI is crucial. In this paper, we employ a deep learning approach to detect RFI present in observation data and propose an improved network structure based on TransUNet. This network leverages the principles of a multi-scale convolutional attention mechanism. It introduces an auxiliary branch to extract high-dimensional image information and an enhanced coordinate attention mechanism for feature map extraction, enabling more comprehensive and accurate identification of RFI in time–frequency images. We introduce a novel architecture named the Multi-Scale TransUNet Network, abbreviated as MS-TransUNet. We utilized observation data from the 40 m radio telescope at the Yunnan Observatory as a data set for training, validating, and testing the network. Compared with previous deep learning networks (U-Net, RFI-Net, R-Net, DSC, EMSCA-UNet), the recall rate and f2 score have been significantly improved. Specifically, the recall rate is improved by at least 2.99%, and the f2 score is improved by at least 2.46%. Experiments demonstrate that this network is exceptional in identifying RFI more comprehensively while ensuring high precision.
|
[
1338,
1938,
1968
] |
[
"radio astronomy",
"convolutional neural networks",
"astronomy data visualization"
] |
2022ApJ...933L...9G
|
Black Hole to Photosphere: 3D GRMHD Simulations of Collapsars Reveal Wobbling and Hybrid Composition Jets
|
Long-duration γ-ray bursts (GRBs) accompany the collapse of massive stars and carry information about the central engine. However, no 3D models have been able to follow these jets from their birth via black hole (BH) to the photosphere. We present the first such 3D general-relativity magnetohydrodynamic simulations, which span over six orders of magnitude in space and time. The collapsing stellar envelope forms an accretion disk, which drags inwardly the magnetic flux that accumulates around the BH, becomes dynamically important, and launches bipolar jets. The jets reach the photosphere at ~10<SUP>12</SUP> cm with an opening angle θ <SUB> j </SUB> ~ 6° and a Lorentz factor Γ<SUB> j </SUB> ≲ 30, unbinding ≳90% of the star. We find that (i) the disk-jet system spontaneously develops misalignment relative to the BH rotational axis. As a result, the jet wobbles with an angle θ <SUB> t </SUB> ~ 12°, which can naturally explain quiescent times in GRB lightcurves. The effective opening angle for detection θ <SUB> j </SUB> + θ <SUB> t </SUB> suggests that the intrinsic GRB rate is lower by an order of magnitude than standard estimates. This suggests that successful GRBs are rarer than currently thought and emerge in only ~0.1% of supernovae Ib/c, implying that jets are either not launched or choked inside most supernova Ib/c progenitors. (ii) The magnetic energy in the jet decreases due to mixing with the star, resulting in jets with a hybrid composition of magnetic and thermal components at the photosphere, where ~10% of the gas maintains magnetization σ ≳ 0.1. This indicates that both a photospheric component and reconnection may play a role in the prompt emission.
|
[
629,
304,
1390,
1607,
1274,
1263,
1730,
1729,
1966
] |
[
"gamma-ray bursts",
"core-collapse supernovae",
"relativistic jets",
"stellar jets",
"polar jets",
"plasma jets",
"type ic supernovae",
"type ib supernovae",
"magnetohydrodynamical simulations"
] |
2020AJ....159...43H
|
Spectroscopically Identified Cataclysmic Variables from the LAMOST Survey. I. The Sample
|
A sample of cataclysmic variables (CVs) is presented including spectroscopically identified 380 spectra of 245 objects, of which 58 CV candidates are new discoveries. The BaggingTopPush and the Random Forest algorithms are applied to the Fifth Data Release (DR5) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) to retrieve CVs with strong emission lines and with broad absorption lines respectively. Based on spectroscopic classification, 134 dwarf novae, 41 nova-like variables, and 19 magnetic CVs are identified from the sample. In addition, 89 high-inclination systems and 33 CVs showing companion stars are recognized and discussed for their distinct spectral characteristics. Comparisons between CVs from LAMOST and from published catalogs are made in spatial and magnitude distribution, and the difference of their locus in the Gaia color-absolute magnitude diagram (CaMD) are also investigated. More interestingly, for two dwarf novae observed through LAMOST and SDSS in different epochs, their spectra both in quiescence phase and during outburst are exhibited.
|
[
203,
418,
1126,
205,
1858
] |
[
"cataclysmic variable stars",
"dwarf novae",
"nova-like variable stars",
"catalogs",
"astronomy data analysis"
] |
2023PSJ.....4....3G
|
CO and CO<SUB>2</SUB> Productions Rates of Comets Observed by NEOWISE within Year 1 of the Reactivated Mission
|
We report on the observed fluxes of the comets detected by NEOWISE during the first year of operations after the spacecraft's reactivation. The sample included 57 comets. Of the comets detected, 30 were short-period comets (27 Jupiter-family comets, 1 Centaur, 2 Halley-type comets), and 27 were long-period comets. From the measured fluxes in the two NEOWISE bands, proxies for the gas production and coma dust are derived. We find a relationship between heliocentric distance, perihelion distance, and the gas-to-dust proxy fractions.
|
[
280,
1452,
933,
786
] |
[
"comets",
"short period comets",
"long period comets",
"infrared astronomy"
] |
2023ApJ...951..106B
|
Precession-induced Variability in AGN Jets and OJ 287
|
The combined study of the flaring of active galactic nuclei (AGNs) at radio wavelengths and parsec-scale jet kinematics with Very Long Baseline Interferometry has led to the view that (i) the observed flares are associated with ejections of synchrotron blobs from the core, and (ii) most of the flaring follows a one-to-one correlation with the ejection of the component. Recent results have added to the mounting evidence showing that the quasi-regular component injections into the relativistic jet may not be the only cause of the flux variability. We propose that AGN flux variability and changes in jet morphology can both be of deterministic nature, i.e., having a geometric/kinetic origin linked to the time-variable Doppler beaming of the jet emission as its direction changes due to precession (and nutation). The physics of the underlying jet leads to shocks, instabilities, or ejections of plasmoids. The appearance (morphology, flux, etc.) of the jet can, however, be strongly affected and modulated by precession. We demonstrate this modulating power of precession for OJ 287. For the first time, we show that the spectral state of the spectral energy distribution (SED) can be directly related to the jet's precession phase. We model the SED evolution and reproduce the precession parameters. Further, we apply our precession model to 11 prominent AGNs. We show that for OJ 287 precession seems to dominate the long-term variability (≳1 yr) of the AGN flux, SED spectral state, and jet morphology, while stochastic processes affect the variability on short timescales (≲0.2 yr).
|
[
16,
164,
1390,
608,
1346,
678
] |
[
"active galactic nuclei",
"blazars",
"relativistic jets",
"galaxy mergers",
"radio interferometry",
"gravitational waves"
] |
2020ApJ...890L..11S
|
Hyperbolic Meteoroids Impacting the Moon
|
Since the discovery of the Moon's asymmetric ejecta cloud, the origin of its sunward-canted density enhancement has not been well understood. We propose impact ejecta from meteoroids on hyperbolic trajectories (β-meteoroids) that hit the Moon's sunward side could explain this unresolved asymmetry. β-meteoroids are submicron in size, comparable to or smaller than the regolith particles they hit, and can impact the Moon at very high speeds ∼100 km s<SUP>-1</SUP>. Therefore, their impact regime may differ from the significantly larger and slower sporadic meteoroids responsible for generating the bulk of the lunar impact ejecta cloud. We compare lunar impact ejecta production to β-meteoroid fluxes observed by multiple spacecraft. If β-meteoroids are able to liberate similar sized submicron particles, orbital dust detector measurements from the Lunar Dust Experiment on board the Lunar Atmosphere and Dust Environment Explorer spacecraft only need to detect one ejecta grain out of every 10<SUP>6</SUP> β-meteoroid impacts to the lunar surface to explain the sunward asymmetry with this additional population. This finding suggests β-meteoroids may also contribute to the evolution of other airless surfaces in the inner solar system, and by extension, at exozodiacal systems.
|
[
236,
821,
1039,
1845,
958,
779,
453
] |
[
"circumstellar dust",
"interplanetary dust",
"meteoroid dust clouds",
"zodiacal cloud",
"lunar impacts",
"impact phenomena",
"ejecta"
] |
2020ApJ...902L..37G
|
Special Supernova Signature from BH-NS/BH Progenitor Systems
|
The gravitational-wave detection by the LIGO-Virgo scientific collaboration shows that black hole and neutron star (BH-NS) or BH-BH systems with a BH mass of tens of solar masses widely exist in the universe. Two main types of scenarios have been invoked for the formation of BH-NS/BH systems, including isolated binary evolution in galactic fields and dynamical interactions in dense environments. Here we propose that if the BH-NS/BH systems are formed from isolated binary evolution, the supernova (SN) signal associated with the second core collapse would show some identifiable features, due to the accretion feedback from the companion BH. Depending on the binary properties, we show that the SN lightcurve could present a sharp peak around ∼10 days, with luminosity even at the level of the super luminous SNe (e.g., $\sim {10}^{44}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ ) or present a plateau feature lasting for several tens of days with regular luminosity of core collapse SNe. Comparing the event rate density of these special SN signals with the event rate density of LIGO-Virgo detected BH-NS/BH systems could help to distinguish the BH-NS/BH formation channel.
|
[
1668,
678,
162,
1108
] |
[
"supernovae",
"gravitational waves",
"black holes",
"neutron stars"
] |
2021ApJ...921..103M
|
Lyα Line Properties at z = 3.78 and Their Environmental Dependence: A Case Study around a Massive Protocluster
|
Lyα-emitting galaxies (LAEs) are easily detectable in the high-redshift universe and are potentially efficient tracers of large-scale structure at early epochs, as long as their observed properties do not depend strongly on environment. We investigate the luminosity and equivalent width functions of LAEs in the overdense field of a protocluster at redshift z ≃ 3.78. Using a large sample of LAEs (many spectroscopically confirmed), we find that the Lyα luminosity distribution is well represented by a Schechter function with $\mathrm{log}({L}^{* }/\mathrm{erg}\ {{\rm{s}}}^{-1})={43.26}_{-0.22}^{+0.20}$ and $\mathrm{log}({\phi }^{* }/{\mathrm{Mpc}}^{-3})=-{3.40}_{-0.04}^{+0.03}$ with α = -1.5. Fitting the equivalent width distribution as an exponential, we find a scale factor of $\omega ={79}_{-15}^{+15}$ Å. We also measured the Lyα luminosity and equivalent width functions using the subset of LAEs lying within the densest cores of the protocluster, finding similar values for L* and ω. Hence, despite having a mean overdensity more than 2× that of the general field, the shapes of the Lyα luminosity function and equivalent width distributions in the protocluster region are comparable to those measured in the field LAE population by other studies at similar redshift. While the observed Lyα luminosities and equivalent widths show correlations with the UV continuum luminosity in this LAE sample, we find that these are likely due to selection biases and are consistent with no intrinsic correlations within the sample. This protocluster sample supports the strong evolutionary trend observed in the Lyα escape fraction and suggests that LAEs at lower redshift can be on average significantly more dusty that their counterparts at higher redshift.
|
[
734,
1297,
942,
1088,
2007
] |
[
"high-redshift galaxies",
"protoclusters",
"luminosity function",
"narrow band photometry",
"high-redshift galaxy clusters"
] |
2020ApJ...891..137Z
|
A Systematic Study of the Dust of Galactic Supernova Remnants. I. The Distance and the Extinction
|
By combining the photometric, spectroscopic, and astrometric information of the stars in the sightline of supernova remnants (SNRs), the distances to and the extinctions of 32 Galactic SNRs are investigated. The stellar atmospheric parameters are from the Sloan Digital Sky Survey-DR14/Apache Point Observatory Galaxy Evolution Experiment and Large sky Area Multi-Object fiber Spectroscopic Telescope-DR5/LEGUE spectroscopic surveys. The multiband photometry, from optical to infrared, are collected from the Gaia, APASS, Pan-STARRS1, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer surveys. With the calibrated Gaia distances of individual stars, the distances to 15 of 32 SNRs are well determined from their produced extinction and association with molecular clouds. The upper limits of distance are derived for three SNRs. The color excess ratios E({g}<SUB>P</SUB>1-λ)/E({g}<SUB>P1</SUB>-{r}<SUB>P1</SUB>) of 32 SNRs are calculated, and their variation with wavebands is fitted by a simple dust model. The inferred dust grain size distribution bifurcates: while the graphite grains have comparable size to the average interstellar medium dust, the silicate grains are generally larger. Along the way, the average extinction law from optical to near-infrared of the Milky Way is derived from the 1.3-million-star sample and found to agree with the CCM89 law with R<SUB>V</SUB>=3.15.
|
[
505,
1667,
836
] |
[
"extinction",
"supernova remnants",
"interstellar dust"
] |
2023ApJ...954..131B
|
The Galaxy-Halo Connection of DESI Luminous Red Galaxies with Subhalo Abundance Matching
|
We use subhalo abundance and age distribution matching to create magnitude-limited mock galaxy catalogs at z ~ 0.43, 0.52, and 0.63 with z-band and 3.4 μm W1-band absolute magnitudes and r - z and r - W1 colors. From these magnitude-limited mocks, we select mock luminous red galaxy (LRG) samples according to the (r - z)-based (optical) and (r - W1)-based (infrared) selection criteria for the LRG sample of the Dark Energy Spectroscopic Instrument (DESI) survey. Our models reproduce the number densities, luminosity functions, color distributions, and projected clustering of the DESI Legacy Surveys that are the basis for DESI LRG target selection. We predict the halo occupation statistics of both optical and IR DESI LRGs at fixed cosmology and assess the differences between the two LRG samples. We find that IR-based SHAM modeling represents the differences between the optical and IR LRG populations better than using the z band and that age distribution matching overpredicts the clustering of LRGs, implying that galaxy color is uncorrelated with halo age in the LRG regime. Both the optical and IR DESI LRG target selections exclude some of the most luminous galaxies that would appear to be LRGs based on their position on the red sequence in optical color-magnitude space. Both selections also yield populations with a nontrivial LRG-halo connection that does not reach unity for the most massive halos. We find that the IR selection achieves greater completeness (≳90%) than the optical selection across all redshift bins studied.
|
[
902,
573
] |
[
"large-scale structure of the universe",
"galaxies"
] |
2020ApJ...897...46F
|
Gravitational-wave Captures by Intermediate-mass Black Holes in Galactic Nuclei
|
Intermediate-mass black holes (IMBHs) have not been detected beyond any reasonable doubt, despite their potential role as massive seeds for quasars and sources of tidal disruption events, ultraluminous X-ray sources, dwarf galaxy feedback, and hypervelocity stars. Gravitational wave (GW) observations can help to find and confirm the existence of IMBHs. Current and upcoming detectors, such as LIGO, Virgo, KAGRA, LISA, ET, and DECIGO promise to identify the full range from stellar-mass to supermassive black holes. In this paper, we address the question of whether IMBHs can produce GWs in galactic nuclei. We consider the possibility that stellar black holes (SBHs) form bound systems and later coalesce with an IMBH through gravitational captures in the dense nucleus. We show that this mechanism is efficient for IMBH masses in the range $\sim 3\times {10}^{3}\,{M}_{\odot }$ - $2\times {10}^{4}\,{M}_{\odot }$ . We find that the typical distributions of peak frequencies and merger timescales depend mainly on the IMBH mass. In particular, the typical peak frequency is about 0.2 Hz, 0.1 Hz, 0.09 Hz, and 0.05 Hz for ${M}_{\mathrm{IMBH}}=5\times {10}^{3}\,{M}_{\odot }$ , $8\times {10}^{3}\,{M}_{\odot }$ , $1\times {10}^{4}\,{M}_{\odot }$ , and $2\times {10}^{4}\,{M}_{\odot }$ , respectively. Our results show that, at design sensitivity, both DECIGO and ET should be able to detect these IMBH-SBH mergers. Furthermore, most of the mergers will appear eccentric (e ≳ 0.1), providing an indication of their dynamical origin.
|
[
676,
678,
602,
565,
816,
98,
159,
591,
677,
1596,
609,
675
] |
[
"gravitational wave detectors",
"gravitational waves",
"galaxy kinematics",
"galactic center",
"intermediate-mass black holes",
"astrophysical black holes",
"black hole physics",
"galaxy dynamics",
"gravitational wave sources",
"stellar dynamics",
"galaxy nuclei",
"gravitational wave astronomy"
] |
2022ApJ...931...75H
|
The SDSS-HET Survey of Kepler Eclipsing Binaries. A Sample of Four Benchmark Binaries
|
The purpose of this work is to extend a sample of accurately modeled, benchmark-grade eclipsing binaries (EBs) with accurately determined masses and radii. We select four "well-behaved" Kepler binaries, KIC 2306740, KIC 4076952, KIC 5193386 and KIC 5288543, each with at least eight double-lined spectra from the Apache Point Observatory Galactic Evolution Experiment instrument that is part of the Sloan Digital Sky Surveys III and IV, and from the Hobby-Eberly High Resolution Spectrograph. We obtain masses and radii with uncertainties of 2.5% or less for all four systems. Three of these systems have orbital periods longer than 9 days, and thus populate an undersampled region of the parameter space for extremely well-characterized detached EBs. We compare the derived masses and radii against MESA MIST isochrones to determine the ages of the systems. All systems were found to be coeval, showing that the results are consistent across MESA MIST and PHOEBE.
|
[
154,
254,
375,
444,
1557,
555
] |
[
"binary stars",
"close binary stars",
"detached binary stars",
"eclipsing binary stars",
"spectroscopic binary stars",
"fundamental parameters of stars"
] |
2021ApJ...908...31Z
|
Chemical Abundances in Sgr A East: Evidence for a Type Iax Supernova Remnant
|
Recent observations have shown a remarkable diversity of observational behaviors and explosion mechanisms in thermonuclear supernovae (SNe). An emerging class of peculiar thermonuclear SNe, called Type Iax, show photometric and spectroscopic behaviors distinct from normal Type Ia. Their origin remains highly controversial, but pure turbulent deflagration of white dwarfs (WDs) has been regarded as the leading formation theory. The large population of Type Iax indicates the existence of unidentified Galactic Type Iax supernova remnants (SNRs). We report evidence that SNR Sgr A East in the Galactic center resulted from a pure turbulent deflagration of a Chandrasekhar-mass carbon-oxygen WD, an explosion mechanism used for Type Iax SNe. Our X-ray spectroscopic study of Sgr A East using 3 Ms of Chandra data shows a low ratio of intermediate-mass elements to Fe and large Mn/Fe and Ni/Fe ratios. This abundance pattern does not accord with the core-collapse or normal Type Ia models. Sgr A East is thus the first Galactic SNR for which a likely Type Iax origin has been proposed and is the nearest target for studying this peculiar class. We compared Sgr A East with the Fe-rich SNRs 3C 397 and W49B, which also have high Mn and Cr abundances and were claimed to result from deflagration-to-detonation explosions of Chandrasekhar-mass WDs (although with disputes). Our study shows that they have distinct abundance patterns. The X-ray spectroscopic studies of thermonuclear SNRs provide observational evidence for the theories that there are diverse explosion channels and various metal outputs for Chandrasekhar-mass WDs.
|
[
1667,
1728,
503,
1799,
565
] |
[
"supernova remnants",
"type ia supernovae",
"explosive nucleosynthesis",
"white dwarf stars",
"galactic center"
] |
2023RNAAS...7...87N
|
Modeling the Transmission and Emission Spectra of K2-18b: Determining the Surfaces of Exoplanets with Hydrogen Dominated Atmospheres
|
Exoplanets between the sizes of Earth and Neptune are abundant in the universe yet absent in our solar system. We do not know if these "sub-Neptune" planets have a surface or how deep their surfaces may be. Recent studies have shown atmospheric chemistry may reflect the surface depth of these planets. In this work, we aim to determine if future observations-at wavelengths and resolutions applicable to JWST-can determine the surface pressure of sub-Neptunes. We present model transmission and emission spectra of the canonical sub-Neptune K2-18b assuming four different surface pressures. The transmission spectra indicate the shallow surface (1 bar) is the most distinguishable from the deeper surfaces, with differences at 2, 4-5, and 10 μm. The emission spectra also show the shallow surface as most distinguishable, noticeably around 3-4 μm.
|
[
2118,
1063,
487,
2172,
498
] |
[
"exoplanet surfaces",
"mini neptunes",
"exoplanet atmospheres",
"extrasolar gaseous planets",
"exoplanets"
] |
2020AJ....160...28G
|
Simulated JWST Data Sets for Multispectral and Hyperspectral Image Fusion
|
The James Webb Space Telescope (JWST) will provide multispectral and hyperspectral infrared images of a large number of astrophysical scenes. Multispectral images will have the highest angular resolution, while hyperspectral images (e.g., with integral field unit spectrometers) will provide the best spectral resolution. This paper aims at providing a comprehensive framework to generate an astrophysical scene and to simulate realistic hyperspectral and multispectral data acquired by two JWST instruments, namely, NIRCam Imager and NIRSpec IFU. We want to show that this simulation framework can be resorted to assess the benefits of fusing these images to recover an image of high spatial and spectral resolutions. To do so, we make a synthetic scene associated with a canonical infrared source, the Orion Bar. We develop forward models including corresponding noises for the two JWST instruments based on their physical features. JWST observations are then simulated by applying the forward models to the aforementioned synthetic scene. We test a dedicated fusion algorithm we developed on these simulated observations. We show that the fusion process reconstructs the high spatio-spectral resolution scene with a good accuracy on most areas, and we identify some limitations of the method to be tackled in future works. The synthetic scene and observations presented in the paper can be used, for instance, to evaluate instrument models, pipelines, or more sophisticated algorithms dedicated to JWST data analysis. Besides, fusion methods such as the one presented in this paper are shown to be promising tools to fully exploit the unprecedented capabilities of the JWST.
|
[
786,
1223,
1858,
387,
1859,
1558
] |
[
"infrared astronomy",
"photodissociation regions",
"astronomy data analysis",
"direct imaging",
"astronomy data modeling",
"spectroscopy"
] |
2021ApJ...910...28W
|
Cosmology with Galaxy Cluster Weak Lensing: Statistical Limits and Experimental Design
|
We forecast constraints on the amplitude of matter clustering σ<SUB>8</SUB>(z) achievable with the combination of cluster weak lensing and number counts, in current and next-generation weak lensing surveys. We advocate for an approach, analogous to galaxy-galaxy lensing, in which the observables in each redshift bin are the mean number counts and the mean weak lensing profile of clusters above a mass proxy threshold. The primary astrophysical nuisance parameter is the logarithmic scatter ${\sigma }_{\mathrm{ln}M}$ between the mass proxy and true mass near the threshold. For surveys similar to the Dark Energy Survey (DES), the Roman Space Telescope High Latitude Survey (HLS), and the Rubin Observatory Legacy Survey of Space and Time (LSST), we forecast aggregate precision on σ<SUB>8</SUB> of 0.26%, 0.24%, and 0.10%, respectively, if the mass-observable scatter is known externally to ${\rm{\Delta }}{\sigma }_{\mathrm{ln}M}\leqslant 0.01$ . These constraints would be degraded by about 20% for ${\rm{\Delta }}{\sigma }_{\mathrm{ln}M}=0.05$ in the case of DES or HLS and for ${\rm{\Delta }}{\sigma }_{\mathrm{ln}M}=0.016$ for LSST. A 1 month observing program with Roman Space Telescope targeting ∼2500 massive clusters could achieve a ∼ 0.5% constraint on σ<SUB>8</SUB>(z = 0.7) on its own, or a ∼ 0.33% constraint in combination with the HLS. Realizing the constraining power of clusters Requires accurate knowledge of the mass-observable relation and stringent control of systematics. We provide analytic approximations to our numerical results that allow for easy scaling to other survey assumptions or other methods of cluster mass estimation.
|
[
584,
343,
1797,
339,
1455
] |
[
"galaxy clusters",
"cosmology",
"weak gravitational lensing",
"cosmological parameters",
"sigma8"
] |
2022ApJ...938L..19G
|
Do High-spin High-mass X-Ray Binaries Contribute to the Population of Merging Binary Black Holes?
|
Gravitational-wave observations of binary black hole (BBH) systems point to black hole spin magnitudes being relatively low. These measurements appear in tension with high spin measurements for high-mass X-ray binaries (HMXBs). We use grids of MESA simulations combined with the rapid population-synthesis code COSMIC to examine the origin of these two binary populations. It has been suggested that Case-A mass transfer while both stars are on the main sequence can form high-spin BHs in HMXBs. Assuming this formation channel, we show that depending on the critical mass ratios for the stability of mass transfer, 48%-100% of these Case-A HMXBs merge during the common-envelope phase and up to 42% result in binaries too wide to merge within a Hubble time. Both MESA and COSMIC show that high-spin HMXBs formed through Case-A mass transfer can only form merging BBHs within a small parameter space where mass transfer can lead to enough orbital shrinkage to merge within a Hubble time. We find that only up to 11% of these Case-A HMXBs result in BBH mergers, and at most 20% of BBH mergers came from Case-A HMXBs. Therefore, it is not surprising that these two spin distributions are observed to be different.
|
[
678,
1611,
1599,
733,
2155
] |
[
"gravitational waves",
"stellar mass black holes",
"stellar evolution",
"high mass x-ray binary stars",
"roche lobe overflow"
] |
2024AJ....168...62W
|
Gaia22dkvLb: A Microlensing Planet Potentially Accessible to Radial-velocity Characterization
|
We report discovering an exoplanet from following up a microlensing event alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the traditional bulge microlensing fields. Our primary analysis yields a Jovian planet with at a projected orbital separation au, and the host is a ∼1.1 M <SUB>⊙</SUB> turnoff star at ∼1.3 kpc. At , the host is far brighter than any previously discovered microlensing planet host, opening up the opportunity to test the microlensing model with radial velocity (RV) observations. RV data can be used to measure the planet's orbital period and eccentricity, and they also enable searching for inner planets of the microlensing cold Jupiter, as expected from the "inner–outer correlation" inferred from Kepler and RV discoveries. Furthermore, we show that Gaia astrometric microlensing will not only allow precise measurements of its angular Einstein radius θ <SUB>E</SUB> but also directly measure the microlens parallax vector and unambiguously break a geometric light-curve degeneracy, leading to the definitive characterization of the lens system.
|
[
2147
] |
[
"gravitational microlensing exoplanet detection"
] |
2022RNAAS...6...90O
|
The Study of Quasar Clustering at Low Redshifts
|
We use a nearest neighbor algorithm combined with the machine learning clustering function Density-Based Spatial Clustering of Applications with Noise to analyze a subset of quasars from the Sloan Digital Sky Survey. Our analysis shows evidence of clustering up to z ~ 2, with evidence of an increase in clustering at lower redshifts (z < 0.5). Our findings may suggest that, over time, the gravitational interaction between quasars has led to more clustering at low redshifts.
|
[
1319,
1908
] |
[
"quasars",
"clustering"
] |
2020ApJ...896...39A
|
Blasts from the Past: Supernova Shock Breakouts among X-Ray Transients in the XMM-Newton Archive
|
The first electromagnetic signal from a supernova (SN) is released when the shock crosses the progenitor surface. This shock breakout (SBO) emission provides constraints on progenitor and explosion properties. Observationally, SBOs appear as minute- to hour-long extragalactic X-ray transients. They are challenging to detect and only one SBO has been observed to date. Here, we search the XMM-Newton archive and find 12 new SN SBO candidates. We identify host galaxies to nine of these at estimated redshifts of 0.1-1. The SBO candidates have energies of ∼10<SUP>46</SUP> erg, timescales of 30-3000 s, and temperatures of 0.1-1 keV. They are all consistent with being SN SBOs, but some may be misidentified Galactic foreground sources or other extragalactic objects. SBOs from blue supergiants agree well with most of the candidates. However, a few could be SBOs from Wolf-Rayet stars surrounded by dense circumstellar media, whereas two are more naturally explained as SBOs from red supergiants. The observations tentatively support non-spherical SBOs and are in agreement with asymmetries predicted by recent three-dimensional SN explosion simulations. eROSITA may detect ∼2 SBOs per year, which could be detected in live analyses and promptly followed up.
|
[
304,
1852,
732,
2086
] |
[
"core-collapse supernovae",
"x-ray transient sources",
"massive stars",
"shocks"
] |
2023ApJ...942...59J
|
(Nearly) Model-independent Constraints on the Neutral Hydrogen Fraction in the Intergalactic Medium at z 5-7 Using Dark Pixel Fractions in Lyα and Lyβ Forests
|
Cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (IGM). Current observations show that the IGM is significantly neutral at z > 7 and largely ionized by z ~ 5.5. However, most methods to measure the IGM neutral fraction are highly model dependent and are limited to when the volume-averaged neutral fraction of the IGM is either relatively low ( ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}\lesssim {10}^{-3}$ ) or close to unity ( ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}\sim 1$ ). In particular, the neutral fraction evolution of the IGM at the critical redshift range of z = 6-7 is poorly constrained. We present new constraints on ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}$ at z ~ 5.1-6.8 by analyzing deep optical spectra of 53 quasars at 5.73 < z < 7.09. We derive model-independent upper limits on the neutral hydrogen fraction based on the fraction of "dark" pixels identified in the Lyα and Lyβ forests, without any assumptions on the IGM model or the intrinsic shape of the quasar continuum. They are the first model-independent constraints on the IGM neutral hydrogen fraction at z ~ 6.2-6.8 using quasar absorption measurements. Our results give upper limits of ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.3)\lt 0.79\pm 0.04$ (1σ), ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.5)\lt 0.87\pm 0.03$ (1σ), and ${\overline{x}}_{{\rm{H}}\,{\rm\small{I}}}(z=6.7)\lt {0.94}_{-0.09}^{+0.06}$ (1σ). The dark pixel fractions at z > 6.1 are consistent with the redshift evolution of the neutral fraction of the IGM derived from Planck 2018.
|
[
1383,
813,
343
] |
[
"reionization",
"intergalactic medium",
"cosmology"
] |
2023ApJ...948..107F
|
Gas Accretion Can Drive Turbulence in Galaxies
|
The driving of turbulence in galaxies is deeply connected with the physics of feedback, star formation, outflows, accretion, and radial transport in disks. The velocity dispersion of gas in galaxies therefore offers a promising observational window into these processes. However, the relative importance of each of these mechanisms remains controversial. In this work we revisit the possibility that turbulence on galactic scales is driven by the direct impact of accreting gaseous material on the disk. We measure this effect in a disk-like star-forming galaxy in IllustrisTNG, using the high-resolution cosmological magnetohydrodynamical simulation TNG50. We employ Lagrangian tracer particles with a high time cadence of only a few million years to identify accretion and other events. The energies of particles are measured by stacking the events in bins of time around the event. The average effect of each event is measured by fitting explicit models for the kinetic and turbulent energies as a function of time. These measurements are corroborated by cross-correlating the turbulent energy with other time series and searching for signals of causality, i.e., asymmetries across zero time lag. We find that accretion contributes to the large-scale turbulent kinetic energy even if it does not dominate in this ~5 × 10<SUP>9</SUP> M <SUB>⊙</SUB> stellar mass galaxy. Extrapolating this finding to a range of galaxy masses, we find that there are regimes where energy from direct accretion may dominate the turbulent energy budget, particularly in disk outskirts, galaxies less massive than the Milky Way, and at redshift ~2.
|
[
612,
614,
591,
595,
734,
391,
1569
] |
[
"galaxy physics",
"galaxy processes",
"galaxy dynamics",
"galaxy formation",
"high-redshift galaxies",
"disk galaxies",
"star formation"
] |
2020ApJ...900..103J
|
A Diffuse Metal-poor Component of the Sagittarius Stream Revealed by the H3 Survey
|
The tidal disruption of the Sagittarius dwarf galaxy has generated a spectacular stream of stars wrapping around the entire Galaxy. We use data from Gaia and the H3 Stellar Spectroscopic Survey to identify $823$ high-quality Sagittarius members based on their angular momenta. The H3 Survey is largely unbiased in metallicity, and so our sample of Sagittarius members is similarly unbiased. Stream stars span a wide range in [Fe/H] from -0.2 to ≈-3.0, with a mean overall metallicity of $\langle [\mathrm{Fe}/{\rm{H}}]\rangle =-0.99$ . We identify a strong metallicity dependence to the kinematics of the stream members. At [Fe/H] > -0.8 nearly all members belong to the well-known cold ( ${\sigma }_{v}\lt 20\,\mathrm{km}\,{{\rm{s}}}^{-1}$ ) leading and trailing arms. At intermediate metallicities (-1.9 < [Fe/H] < -0.8) a significant population (24%) emerges of stars that are kinematically offset from the cold arms. These stars also appear to have hotter kinematics. At the lowest metallicities ([Fe/H] ≲ -2), the majority of stars (69%) belong to this kinematically offset diffuse population. Comparison to simulations suggests that the diffuse component was stripped from the Sagittarius progenitor at earlier epochs, and therefore resided at larger radius on average than the colder metal-rich component. We speculate that this kinematically diffuse, low-metallicity population is the stellar halo of the Sagittarius progenitor system.
|
[
1054,
416,
1696,
1423
] |
[
"milky way galaxy",
"dwarf galaxies",
"tidal disruption",
"sagittarius dwarf spheroidal galaxy"
] |
2024ApJ...969...70F
|
The Stability of Dense Cores near the Serpens South Protocluster
|
Most stars form in clusters and groups rather than in isolation. We present ≲5″ angular resolution (∼2000 au, or 0.01 pc) Very Large Array NH<SUB>3</SUB> (1,1), (2,2), and (3,3) and 1.3 cm continuum emission observations of the dense gas within the Serpens South protocluster and extended filaments to the north and south. We identify 94 dense cores using a dendrogram analysis of the NH<SUB>3</SUB> (1,1) integrated intensity. Gas temperatures T <SUB> K </SUB> and nonthermal line widths σ <SUB>NT</SUB> both increase toward the center of the young stellar cluster, in the dense gas generally and in the cores specifically. We find that most cores (54%) are supervirial, with gravitationally bound cores located primarily in the filaments. Cores in the protocluster have higher virial parameters by a factor of ∼1.7, driven primarily by the increased core σ <SUB>NT</SUB> values. These cores cannot collapse to form stars unless they accrete additional mass or their core internal motions are reduced. The southern filament shows a significant velocity gradient previously interpreted as mass flow toward the cluster. We find more complex kinematics in the northern filament. We find a strong correlation between σ <SUB>NT</SUB> and T <SUB> K </SUB>, and argue that the enhanced temperatures and nonthermal motions are due to mechanical heating and interaction between the protocluster-driven outflows and the dense gas. Filament-led accretion may also contribute to the increased σ <SUB>NT</SUB> values. Assuming a constant fraction of core mass ends up in the young stars, future star formation in the Serpens South protocluster will shift to higher masses by a factor of ∼2.
|
[
1569,
849,
1833,
1072,
847
] |
[
"star formation",
"interstellar molecules",
"young star clusters",
"molecular clouds",
"interstellar medium"
] |
2022ApJ...941...57P
|
Explaining the Moderate UV/X-Ray Correlation in AGN
|
The UV/optical and X-ray variability of active galactic nuclei (AGN) have long been expected to be well correlated as a result of the X-ray illumination of the accretion disk. Recent monitoring campaigns of nearby AGN, however, found that their X-ray and UV/optical emission are only moderately correlated, challenging the aforementioned paradigm. In this work, we aim to demonstrate that due to the definition of the cross-correlation function, a low UV/X-ray correlation is well expected in the case of an X-ray illuminated accretion disk, when the dynamic variability of the X-ray source is taken into account. In particular, we examine how the variability of the geometric or physical configuration of the X-ray source affects the expected correlation. Variations of the geometric configuration are found to produce a range of UV/X-ray cross correlations, which match well the observed values, while they result in a high correlation between the UV and optical variability, reconciling the observed results with theoretical predictions. We conclude that the detection of a low UV/X-ray correlation does not contradict the assumption of the UV/optical variability being driven by the X-ray illumination of the disk, and we discuss the implications of our results for correlation studies.
|
[
16,
1447
] |
[
"active galactic nuclei",
"seyfert galaxies"
] |
2023RNAAS...7..249D
|
Second-generation Fragments of a Comet Split in the Making: The Liller Family Comets
|
Kreutz sungrazers and Kracht, Marsden, and Meyer sunskirters are regarded as second- or third-generation fragments of split comets. First-generation fragments have been observed to form, for example, in the cases of comets 73P/Schwassmann-Wachmann 3, D/1993 F2 (Shoemaker-Levy 9), and 332P/Ikeya-Murakami. Here, we compare relevant orbital correlation properties (the distributions of mutual nodal distances, and the angular separation of perihelia and poles) of the Liller family comets-C/1988 A1 (Liller), C/1996 Q1 (Tabur), C/2015 F3 (SWAN), C/2019 Y1 (ATLAS), and C/2023 V5 (Leonard)-with those of fragments of 332P and some Kreutz sungrazers to show that they are first-generation cometary fragments in the process of producing the second-generation.
|
[
280
] |
[
"comets"
] |
2021ApJ...910...64K
|
Identifying Radio-active Galactic Nuclei among Radio-emitting Galaxies
|
Basing our analysis on ROGUE I, a catalog of over 32,000 radio sources associated with optical galaxies, we provide two diagnostics to select the galaxies where the radio emission is dominated by an active galactic nucleus (AGN), referred to in the paper as radio-AGNs. Each of these diagnostics can be applied independently. The first one, dubbed MIRAD, compares the flux F<SUB>W3</SUB> in the W3 mid-infrared band of the Wide-field Infrared Survey Explorer telescope, with the radio flux at 1.4 GHz, F<SUB>1.4</SUB>. MIRAD requires no optical spectra. The second diagnostic, dubbed DLM, compares the 4000 Å break strength, D<SUB>n</SUB>(4000), with the radio luminosity per unit stellar mass. The DLM diagram has already been used in the past, but not as stand-alone. For these two diagrams, we propose simple, empirical dividing lines that result in the same classification for the objects in common. These lines correctly classify as radio-AGN 99.5% of the extended radio sources in the ROGUE I catalog, and as star-forming galaxies 98%-99% of the galaxies identified as such by their emission-line ratios. Both diagrams clearly show that radio-AGNs are preferentially found among elliptical galaxies and among galaxies hosting the most massive black holes. Most of the radio sources classified as radio-AGNs in the MIRAD or DLM diagrams are either optically weak AGNs or retired galaxies.
|
[
1671,
1043,
205,
1343,
2134
] |
[
"surveys",
"astronomical methods",
"catalogs",
"radio galaxies",
"radio active galactic nuclei"
] |
2020ApJS..250....7J
|
Completing the 3CR Chandra Snapshot Survey: Extragalactic Radio Sources at High Redshift
|
We present the analysis of nine radio sources belonging to the Third Cambridge Revised catalog (3CR) observed with Chandra during Cycle 20 in the redshift range between 1.5 and 2.5. This study completes the 3CR Chandra Snapshot Survey thus guaranteeing the X-ray coverage of all 3CR sources identified to date. This sample lists two compact steep spectrum sources, four radio galaxies, and three quasars. We detected X-ray emission from all nuclei, with the only exception of 3C 326.1 and 3C 454.1 and from radio lobes in six out of nine sources at a level of confidence larger than ∼5σ. We measured X-ray fluxes and luminosities for all nuclei and lobes in the soft (0.5-1 keV), medium (1-2 keV), and hard (2-7 keV) X-ray bands. Since the discovered X-ray extended emission is spatially coincident with the radio structure in all cases, its origin could be due to inverse Compton (IC) scattering of the cosmic microwave background (CMB) occurring in radio lobes.
|
[
16,
17,
739,
2134,
2035,
1358
] |
[
"active galactic nuclei",
"active galaxies",
"high energy astrophysics",
"radio active galactic nuclei",
"x-ray active galactic nuclei",
"radio sources"
] |
2021ApJS..253...47K
|
Inferring Solar Differential Rotation through Normal-mode Coupling Using Bayesian Statistics
|
Normal-mode helioseismic data analysis uses observed solar oscillation spectra to infer perturbations in the solar interior due to global and local-scale flows and structural asphericity. Differential rotation, the dominant global-scale axisymmetric perturbation, has been tightly constrained primarily using measurements of frequency splittings via "a-coefficients." However, the frequency-splitting formalism invokes the approximation that multiplets are isolated. This assumption is inaccurate for modes at high angular degrees. Analyzing eigenfunction corrections, which respect cross-coupling of modes across multiplets, is a more accurate approach. However, applying standard inversion techniques using these cross-spectral measurements yields a-coefficients with a significantly wider spread than the well-constrained results from frequency splittings. In this study, we apply Bayesian statistics to infer a-coefficients due to differential rotation from cross-spectra for both f-modes and p-modes. We demonstrate that this technique works reasonably well for modes with angular degrees ℓ = 50-291. The inferred a<SUB>3</SUB>-coefficients are found to be within 1 nHz of the frequency-splitting values for ℓ > 200. We also show that the technique fails at ℓ < 50 owing to the insensitivity of the measurement to the perturbation. These results serve to further establish mode-coupling as an important helioseismic technique with which to infer internal structure and dynamics, both axisymmetric (e.g., meridional circulation) and non-axisymmetric perturbations.
|
[
709,
1515,
1996,
1889
] |
[
"helioseismology",
"solar oscillations",
"solar differential rotation",
"markov chain monte carlo"
] |
2022ApJ...940..133G
|
The Correlation between WISE 12 μm Emission and Molecular Gas Tracers on Subkiloparsec Scales in Nearby Star-forming Galaxies
|
We complement the MALATANG sample of dense gas in nearby galaxies with archival observations of <SUP>12</SUP>CO and its isotopologues to determine scaling relations between Wide-field Infrared Survey Explorer (WISE) 12 μm emission and molecular gas tracers at subkiloparsec scales. We find that 12 μm luminosity is more tightly correlated with <SUP>12</SUP>CO than it is with <SUP>13</SUP>CO or dense gas tracers. Residuals between predicted and observed <SUP>12</SUP>CO are only weakly correlated with molecular gas mass surface density (Σ<SUB>mol</SUB>) in regions where Σ<SUB>mol</SUB> is very low (~10 M <SUB>⊙</SUB> pc<SUP>-2</SUP>). Above this limit, the <SUP>12</SUP>CO residuals show no correlations with physical conditions of molecular gas, while <SUP>13</SUP>CO residuals depend on the gas optical depth and temperature. By analyzing differences from galaxy to galaxy, we confirm that the <SUP>12</SUP>CO-12 μm relation is strong and statistically robust with respect to star-forming galaxies and active galactic nucleus hosts. These results suggest that WISE 12 μm emission can be used to trace total molecular gas instead of dense molecular gas, likely because polycyclic aromatic hydrocarbons (PAHs, a major contributor to WISE 12 μm emission) may be well mixed with the gas that is traced by <SUP>12</SUP>CO. We propose that WISE 12 μm luminosity can be used to estimate molecular gas surface density for statistical analyses of the star formation process in galaxies.
|
[
1280,
262,
1073,
594
] |
[
"polycyclic aromatic hydrocarbons",
"co line emission",
"molecular gas",
"galaxy evolution"
] |
2022ApJ...927L..31R
|
Gaia 0007-1605: An Old Triple System with an Inner Brown Dwarf-White Dwarf Binary and an Outer White Dwarf Companion
|
We identify Gaia 0007-1605 A,C as the first inner brown dwarf-white dwarf binary of a hierarchical triple system in which the outer component is another white dwarf (Gaia 0007-1605 B). From optical/near-infrared spectroscopy obtained at the Very Large Telescope with the X-Shooter instrument and/or from Gaia photometry plus spectral energy distribution fitting, we determine the effective temperatures and masses of the two white dwarfs (12,018 ± 68 K and 0.54 ± 0.01 M <SUB>⊙</SUB> for Gaia 0007-1605 A and 4445 ± 116 K and 0.56 ± 0.05 M <SUB>⊙</SUB> for Gaia 0007-1605 B) and the effective temperature of the brown dwarf (1850 ± 50 K; corresponding to spectral type L3 ± 1). By analyzing the available TESS light curves of Gaia 0007-1605 A,C we detect a signal at 1.0446 ± 0.0015 days with an amplitude of 6.25 ppt, which we interpret as the orbital period modulated from irradiation effects of the white dwarf on the brown dwarf's surface. This drives us to speculate that the inner binary evolved through a common-envelope phase in the past. Using the outer white dwarf as a cosmochronometer and analyzing the kinematic properties of the system, we conclude that the triple system is about 10 Gyr old.
|
[
1799,
1714,
185
] |
[
"white dwarf stars",
"trinary stars",
"brown dwarfs"
] |
2023ApJ...958L..30R
|
XUE: Molecular Inventory in the Inner Region of an Extremely Irradiated Protoplanetary Disk
|
We present the first results of the eXtreme UV Environments (XUE) James Webb Space Telescope (JWST) program, which focuses on the characterization of planet-forming disks in massive star-forming regions. These regions are likely representative of the environment in which most planetary systems formed. Understanding the impact of environment on planet formation is critical in order to gain insights into the diversity of the observed exoplanet populations. XUE targets 15 disks in three areas of NGC 6357, which hosts numerous massive OB stars, including some of the most massive stars in our Galaxy. Thanks to JWST, we can, for the first time, study the effect of external irradiation on the inner (<10 au), terrestrial-planet-forming regions of protoplanetary disks. In this study, we report on the detection of abundant water, CO, <SUP>12</SUP>CO<SUB>2</SUB>, HCN, and C<SUB>2</SUB>H<SUB>2</SUB> in the inner few au of XUE 1, a highly irradiated disk in NGC 6357. In addition, small, partially crystalline silicate dust is present at the disk surface. The derived column densities, the oxygen-dominated gas-phase chemistry, and the presence of silicate dust are surprisingly similar to those found in inner disks located in nearby, relatively isolated low-mass star-forming regions. Our findings imply that the inner regions of highly irradiated disks can retain similar physical and chemical conditions to disks in low-mass star-forming regions, thus broadening the range of environments with similar conditions for inner disk rocky planet formation to the most extreme star-forming regions in our Galaxy.
|
[
1300,
1290,
1241
] |
[
"protoplanetary disks",
"pre-main sequence stars",
"planet formation"
] |
2024ApJ...968..119X
|
Investigating the Unique Drift Behavior of PSR B2110+27 with FAST
|
Careful scrutiny of the single pulse emissions from PSR B2110+27 has been conducted through highly sensitive observations using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at a central frequency of 1250 MHz. Our investigation revealed significant subpulse drift behavior and nulling in this pulsar. Moreover, we observed that the nulling events tend to be of short duration, with an estimated overall nulling fraction of approximately 27% ± 3%. It is noteworthy that the drift direction of the subpulses exhibits abrupt changes, occasionally transitioning into a steady state or displaying a low drift rate. Analysis using longitude resolved fluctuation spectra indicates the presence of two distinct repetition periods for the pulsar: P <SUB>3</SUB> = (10.8 ± 2.5)P and P <SUB>3</SUB> = (31.6 ± 4.2)P, where P denotes the pulsar period. Our investigation revealed that the subpulse separation remains consistent across different drift patterns, with P <SUB>2</SUB> = 2.°3 ± 0.°2. A more comprehensive analysis indicates that the unique drift behavior observed can be explained by a carousel model of the dipole field. Minor changes in P <SUB>2</SUB> and drift rate caused significant variations in the apparent P <SUB>3</SUB> and abrupt shifts in the drift direction, while the true repetition period (assuming first-order aliasing) changed by only ∼10%. We observe a drift band memory and apparent phase memory across the null state in this pulsar, as well as variations in the drift rate and drift direction across the null state, though we have not detected significant periodicity of the nulling itself. This suggests that these phenomena may arise from random null pulses intersecting with the frequently aliased drift bands.
|
[
1353
] |
[
"radio pulsars"
] |
2023ApJ...951...74Z
|
High-energy Neutrino Production from AGN Disk Transients Impacted by the Circum-disk Medium
|
Various supernovae, compact object coalescences, and tidal disruption events are widely believed to occur embedded in active galactic nucleus (AGN) accretion disks and generate detectable electromagnetic signals. We collectively refer to them as AGN disk transients. The inelastic hadronuclear (pp) interactions between shock-accelerated cosmic rays and AGN disk materials shortly after the ejecta shock breaks out of the disk can produce high-energy neutrinos. However, the expected efficiency of neutrino production would decay rapidly by adopting a pure Gaussian density atmosphere profile applicable for stable gas-dominated disks. On the other hand, AGN outflows and disk winds are commonly found around AGN accretion disks. In this paper, we show that the circum-disk medium would further consume the shock kinetic energy to more efficiently produce high-energy neutrinos, especially for ~ TeV-PeV neutrinos that IceCube detects. Thanks to the existence of the circum-disk medium, we find that the neutrino production will be enhanced significantly and make a much higher contribution to the diffuse neutrino background. Optimistically, ~20% of the diffuse neutrino background can be contributed by AGN disk transients.
|
[
338,
1668,
16,
1799,
1108,
162,
678
] |
[
"cosmological neutrinos",
"supernovae",
"active galactic nuclei",
"white dwarf stars",
"neutron stars",
"black holes",
"gravitational waves"
] |
2020ApJ...893..165C
|
The Role of Quasar Radiative Feedback on Galaxy Formation during Cosmic Reionization
|
Recent observations have found that many z ∼ 6 quasar fields lack galaxies. This unexpected lack of galaxies may potentially be explained by quasar radiation feedback. In this paper, I present a suite of 3D radiative transfer cosmological simulations of quasar fields. I find that quasar radiation suppresses star formation in low-mass galaxies, mainly by photodissociating their molecular hydrogen. Photo-heating also plays a role, but only after ∼100 Myr. However, galaxies that already have stellar mass above 10<SUP>5</SUP>M<SUB>⊙</SUB> when the quasar turns on will not be suppressed significantly. Quasar radiative feedback suppresses the faint end of the galaxy luminosity function (LF) within 1 pMpc, but to a far lesser degree than the field-to-field variation of the LF. My study also suggests that by using the number of bright galaxies ( ${M}_{1500}$ < -16) around quasars, we can potentially recover the underlying mass overdensity, which allows us to put reliable constraints on quasar environments.
|
[
1383,
1319,
573,
595,
734
] |
[
"reionization",
"quasars",
"galaxies",
"galaxy formation",
"high-redshift galaxies"
] |
2023ApJ...943...74S
|
Filtration of Interstellar Neutral Helium by Elastic and Charge Exchange Collisions in Heliospheric Boundaries
|
Interstellar neutral (ISN) helium atoms penetrating the heliosphere are used to find the flow velocity and temperature of the very local interstellar medium near the heliosphere. Recently, it was found that, in addition to charge exchange collisions, elastic collisions contribute to the filtration of these atoms outside the heliopause. Momentum exchange between colliding particles related to their angular scattering modifies the properties of the primary and secondary ISN helium populations before the atoms enter the heliosphere. Here, we calculate the transport of ISN helium atoms using plasma and neutral flows from a global three-dimensional heliosphere model. We confirm earlier results based on one-dimensional calculations that the primary population is slowed down and heated by the momentum exchange. Moreover, accounting for momentum exchange in charge exchange collisions results in a faster and warmer secondary population. The paper presents how the velocity and density of these populations vary over the entrance position to the heliosphere. We point out that Maxwell distributions cannot correctly describe these populations. Finally, we calculate the expected Interstellar Boundary Explorer (IBEX) count rates and show that the filtration processes change them significantly. Consequently, future studies of IBEX or Interstellar Mapping and Acceleration Probe (IMAP) observations of ISN atoms should account for these processes.
|
[
833,
847,
711,
848,
2065,
2218,
2263,
710
] |
[
"interstellar atomic gas",
"interstellar medium",
"heliosphere",
"interstellar medium wind",
"collision physics",
"charge transfer",
"ion-neutral reactions",
"heliosheath"
] |
2022ApJ...938L..11A
|
Searching for High-energy Neutrino Emission from Galaxy Clusters with IceCube
|
Galaxy clusters have the potential to accelerate cosmic rays (CRs) to ultrahigh energies via accretion shocks or embedded CR acceleration sites. The CRs with energies below the Hillas condition will be confined within the cluster and eventually interact with the intracluster medium gas to produce secondary neutrinos and gamma rays. Using 9.5 yr of muon neutrino track events from the IceCube Neutrino Observatory, we report the results of a stacking analysis of 1094 galaxy clusters with masses ≳10<SUP>14</SUP> M <SUB>⊙</SUB> and redshifts between 0.01 and ~1 detected by the Planck mission via the Sunyaev-Zel'dovich effect. We find no evidence for significant neutrino emission and report upper limits on the cumulative unresolved neutrino flux from massive galaxy clusters after accounting for the completeness of the catalog up to a redshift of 2, assuming three different weighting scenarios for the stacking and three different power-law spectra. Weighting the sources according to mass and distance, we set upper limits at a 90% confidence level that constrain the flux of neutrinos from massive galaxy clusters (≳10<SUP>14</SUP> M <SUB>⊙</SUB>) to be no more than 4.6% of the diffuse IceCube observations at 100 TeV, assuming an unbroken E <SUP>-2.5</SUP> power-law spectrum.
|
[
1100,
2007
] |
[
"neutrino astronomy",
"high-redshift galaxy clusters"
] |
2020ApJ...891..128M
|
A Transition of Dynamo Modes in M Dwarfs: Narrowing Down the Spectral Range Where the Transition Occurs
|
Houdebine et al. combined Ca II data with projected rotational velocities (V sin I) to construct rotation-activity correlations (RAC) in K-M dwarfs. The RAC slopes were used to argue that a transition between dynamo modes occurs at a spectral type between M2 and M3. H17 suggested that the dynamo transition corresponds to a transition to complete convection (TTCC). An independent study of GAIA data led Jao et al. to suggest that the TTCC sets in "near M3.0V," close to the H17 result. However, the changes in a star that cause TTCC signatures in GAIA data might not lead to changes in Ca II emission at an identical spectral type: the latter are also affected by magnetic effects, which depend on certain properties of convection in the core. Here, we use Ca II emission fluxes in a sample of ∼600 M dwarfs, and attempt to narrow down the transition from one dynamo mode to another: rather than relying on RAC slopes, we quantify how the Ca II emission flux varies with spectral type to identify "steps" where the flux decreases significantly across a narrow range of spectral types. We suggest that the dynamo mode transition may be narrowed down to between M2.1 and M2.3. This is close to, but earlier than, the TTCC location identified by Jao et al. We suggest that the transition in dynamo mode may be related to the existence of a small convective core, which occurs for a finite time interval in certain low-mass stars.
|
[
104,
230
] |
[
"astrophysical processes",
"stellar chromospheres"
] |
2021AJ....161...20P
|
Double Image Polarimeter—Ultra Fast: Simultaneous Three-color (BV R) Polarimeter with Electron-multiplying Charge-coupled Devices
|
We describe a new instrument capable of high-precision (10<SUP>-5</SUP>) polarimetric observations simultaneously in three passbands (BVR). The instrument utilizes electron-multiplying charge-coupled device (EM CCD) cameras for high efficiency and fast image readout. The key features of the Double Image Polarimeter—Ultra Fast (DIPol-UF) are: (i) the optical design with high throughput and inherent stability; (ii) great versatility, which makes the instrument optimally suitable for observations of bright and faint targets; and (iii) a control system, which allows the use of the polarimeter remotely. Examples are given of the first results obtained from high signal-to-noise observations of bright nearby stars and of fainter sources such as X-ray binaries in their quiescent states.
|
[
1145,
1277,
2030,
1278,
739,
162,
154
] |
[
"observational astronomy",
"polarimeters",
"photometer",
"polarimetry",
"high energy astrophysics",
"black holes",
"binary stars"
] |
2022ApJ...933..164G
|
Shock Breakout in Three-dimensional Red Supergiant Envelopes
|
Using Athena++, we perform 3D radiation-hydrodynamic calculations of the radiative breakout of the shock wave in the outer envelope of a red supergiant (RSG) that has suffered core collapse and will become a Type IIP supernova. The intrinsically 3D structure of the fully convective RSG envelope yields key differences in the brightness and duration of the shock breakout (SBO) from that predicted in a 1D stellar model. First, the lower-density "halo" of material outside of the traditional photosphere in 3D models leads to a shock breakout at lower densities than 1D models. This would prolong the duration of the shock breakout flash at any given location on the surface to ≈1-2 hr. However, we find that the even larger impact is the intrinsically 3D effect associated with large-scale fluctuations in density that cause the shock to break out at different radii at different times. This substantially prolongs the SBO duration to ≈3-6 hr and implies a diversity of radiative temperatures, as different patches across the stellar surface are at different stages of their radiative breakout and cooling at any given time. These predicted durations are in better agreement with existing observations of SBO. The longer durations lower the predicted luminosities by a factor of 3-10 (L <SUB>bol</SUB> ~ 10<SUP>44</SUP> erg s<SUP>-1</SUP>), and we derive the new scalings of brightness and duration with explosion energies and stellar properties. These intrinsically 3D properties eliminate the possibility of using observed rise times to measure the stellar radius via light-travel time effects.
|
[
1668,
1731,
767,
732,
1335
] |
[
"supernovae",
"type ii supernovae",
"hydrodynamical simulations",
"massive stars",
"radiative transfer"
] |
2020ApJ...893L..21R
|
Constraining the Dense Matter Equation of State with Joint Analysis of NICER and LIGO/Virgo Measurements
|
The Neutron Star Interior Composition Explorer collaboration recently published a joint estimate of the mass and the radius of PSR J0030+0451, derived via X-ray pulse-profile modeling. Raaijmakers et al. explored the implications of this measurement for the dense matter equation of state (EOS) using two parameterizations of the high-density EOS: a piecewise-polytropic model, and a model based on the speed of sound in neutron stars (NSs). In this work we obtain further constraints on the EOS following this approach, but we also include information about the tidal deformability of NSs from the gravitational wave signal of the compact binary merger GW170817. We compare the constraints on the EOS to those set by the recent measurement of a 2.14 M<SUB>⊙</SUB> pulsar, included as a likelihood function approximated by a Gaussian, and find a small increase in information gain. To show the flexibility of our method, we also explore the possibility that GW170817 was a NS-black hole merger, which yields weaker constraints on the EOS.
|
[
1107,
678,
1062,
1408,
1900,
2077,
1129,
1810
] |
[
"neutron star cores",
"gravitational waves",
"millisecond pulsars",
"rotation powered pulsars",
"bayesian statistics",
"nuclear physics",
"nuclear astrophysics",
"x-ray astronomy"
] |
2022RNAAS...6..197P
|
Breakthrough Listen Search for the WOW! Signal
|
Caballero identified the star 2MASS 19281982-2640123 as a potential Sun-like star from which the WOW! signal could have originated. We conducted a search for artificial narrowband (2.79 Hz/1.91 Hz), drifting (±4 Hz s<SUP>-1</SUP>) technosignatures from this source using the TURBOSETI pipeline, from 1-2 GHz, using simultaneous multi-telescope observations with both the Robert C. Byrd Green Bank Telescope and the newly refurbished Allen Telescope Array on 2022 May 21. Both telescope observations had an overlap of 580 s. While blind searches using radio telescopes have been conducted in the general field of view in which the WOW! signal was first detected, this is the first time a targeted search has been done. No technosignature candidates were detected. *Dedicated to the memory of Bart S. Wlodarczyk-Sroka.
|
[
2128,
2127,
1338,
2018
] |
[
"technosignatures",
"search for extraterrestrial intelligence",
"radio astronomy",
"biosignatures"
] |
2024ApJ...961...39S
|
Nature versus Nurture: Revisiting the Environmental Impact on Star Formation Activities of Galaxies
|
We present a systematic study of the environmental impact on star formation activities of galaxies using a mass-complete sample of ~170k galaxies at z < 4 from the latest COSMOS2020 catalog. At z < 1, we find that the mean star formation rate (SFR) of all galaxies decreases with increasing density of the environment. However, when we only consider star-forming galaxies, the mean SFR becomes independent of the environment at z < 1. At z > 2, we observe a clear positive correlation between the SFR and the density of the environment for all the galaxies. On the other hand, the stellar mass of the galaxies increases significantly with the environment at all redshifts except for star-forming galaxies at z < 1. The fraction of quiescent galaxies increases with increasing density of the environment at z < 2, and the morphology-density relation is confirmed to be present up to z ~ 1. We also find that environmental quenching is negligible at z > 1, whereas mass quenching is the dominant quenching mechanism for massive galaxies at all redshifts. Based on these results, we argue that stellar mass-regulated physical processes might be the major driving force for star formation activities of galaxies. At low redshift (z < 1) massive galaxies are quenched primarily due to their high mass, resulting in a normal SFR-density relation. At high redshift (z > 2) most of the galaxies are star-forming ones tightly following the star-forming main sequence, and the difference in their stellar mass in different environments naturally leads to a reversal of the SFR-density relation.
|
[
2029
] |
[
"galaxy environments"
] |
2023ApJ...958..157C
|
TREX: Kinematic Characterization of a High-dispersion Intermediate-age Stellar Component in M33
|
The dwarf galaxy Triangulum (M33) presents an interesting testbed for studying stellar halo formation: it is sufficiently massive so as to have likely accreted smaller satellites, but also lies within the regime where feedback and other "in situ" formation mechanisms are expected to play a role. In this work, we analyze the line-of-sight kinematics of stars across M33 from the TREX survey, with a view to understanding the origin of its halo. We split our sample into two broad populations of varying age, comprising 2032 "old" red giant branch stars and 671 "intermediate-age" asymptotic giant branch and carbon stars. We find decisive evidence for two distinct kinematic components in both the old and intermediate-age populations: a low-dispersion (~22 km s<SUP>-1</SUP>) disk-like component corotating with M33's H I gas and a significantly higher-dispersion component (~50-60 km s<SUP>-1</SUP>) that does not rotate in the same plane as the gas and is thus interpreted as M33's stellar halo. While kinematically similar, the fraction of stars associated with the halo component differs significantly between the two populations: this is consistently ~10% for the intermediate-age population, but decreases from ~34% to ~10% as a function of radius for the old population. We additionally find evidence that the intermediate-age halo population is systematically offset from the systemic velocity of M33 by ~25 km s<SUP>-1</SUP>, with a preferred central LOS velocity of ~ - 155 km s<SUP>-1</SUP>. This is the first detection and characterization of an intermediate-age halo in M33, and suggests in situ formation mechanisms, as well as potentially tidal interactions, have helped shaped it.
|
[
1712,
598,
602
] |
[
"triangulum galaxy",
"galaxy stellar halos",
"galaxy kinematics"
] |
2022ApJ...935...76Z
|
Catching the Butterfly and the Homunculus of η Carinae with ALMA
|
The nature and origin of the molecular gas component located in the circumstellar vicinity of η Carinae are still far from being completely understood. Here, we present Atacama Large Millimeter/submillimeter Array CO(3-2) observations with a high angular resolution (~0.″15) and a great sensitivity that are employed to reveal the origin of this component in η Carinae. These observations reveal much higher velocity (-300 to +270 km s<SUP>-1</SUP>) blue- and redshifted molecular thermal emission than previously reported, which we associate with the lobes of the Homunculus Nebula, and which delineates very well the innermost contours of the red- and blueshifted lobes likely due to limb brightening. The inner contour of the redshifted emission was proposed to be a disrupted torus, but here we reveal that it is at least part of the molecular emission originating from the lobes and/or the expanding equatorial skirt. On the other hand, closer to systemic velocities (±100 km s<SUP>-1</SUP>), the CO molecular gas traces an inner butterfly-shaped structure that is also revealed at near-IR and mid-IR wavelengths as the region in which the shielded dust resides. The location and kinematics of the molecular component indicate that this material has formed after the different eruptions of η Carinae.
|
[
481
] |
[
"evolved stars"
] |
2024ApJ...968..128R
|
Role of Polycyclic Aromatic Hydrocarbons with Edge Defects in Explaining Astronomical Infrared Emission Observations
|
A systematic study was performed on the spectral properties of polycyclic aromatic hydrocarbons (PAHs) with edge defects using harmonic density functional theory calculations. Their potential astronomical relevance was assessed through direct comparison with NIRSpec and MIRI-MRS spectra of the atomic photodissociation region of the Orion Bar from the JWST Early Release Science PDRs4All program. It is found that the astronomical 6.2 μm PAH emission band, including its blue side, is well reproduced by PAHs with edge defects, when taking into account the effects of polarization in the computations, and without a need for PAHs that contain nitrogen. Small neutral PAHs with edge defects explain the blue wing of the 3.3 μm band. A low number of edge defects is required to reproduce the 8.6 and 11.2 μm band profiles, while the 11.0 + 11.2/12.7 μm band intensity ratio is a measure for the number of edge defects. A blind database fit to the Orion Bar spectrum reproduces the 6–15 μm region with an error of 9.9% and shows a clear delineation of charge, with the 6–10 μm PAH bands being carried by PAH cations and the 10–15 μm region by predominantly neutral PAHs. The contribution of anions is negligible. Armchair PAHs fit the 12.7 μm band, simultaneously producing a very weak broad emission feature centered at 3.225 μm. Zigzag PAHs fit the 11.2 μm band. It is concluded that PAHs with a low number of edge defects, in addition to armchair and zigzag PAHs, all contribute to the observed interstellar infrared emission.
|
[
786,
2095
] |
[
"infrared astronomy",
"molecular spectroscopy"
] |
2024ApJ...970L..21A
|
Very-high-energy γ-Ray Emission from Young Massive Star Clusters in the Large Magellanic Cloud
|
The Tarantula Nebula in the Large Magellanic Cloud is known for its high star formation activity. At its center lies the young massive star cluster R136, providing a significant amount of the energy that makes the nebula shine so brightly at many wavelengths. Recently, young massive star clusters have been suggested to also efficiently produce very high-energy cosmic rays, potentially beyond PeV energies. Here, we report the detection of very-high-energy γ-ray emission from the direction of R136 with the High Energy Stereoscopic System, achieved through a multicomponent, likelihood-based modeling of the data. This supports the hypothesis that R136 is indeed a very powerful cosmic-ray accelerator. Moreover, from the same analysis, we provide an updated measurement of the γ-ray emission from 30 Dor C, the only superbubble detected at TeV energies presently. The γ-ray luminosity above 0.5 TeV of both sources is (2–3) × 10<SUP>35</SUP> erg s<SUP>‑1</SUP>. This exceeds by more than a factor of 2 the luminosity of HESS J1646‑458, which is associated with the most massive young star cluster in the Milky Way, Westerlund 1. Furthermore, the γ-ray emission from each source is extended with a significance of >3σ and a Gaussian width of about 30 pc. For 30 Dor C, a connection between the γ-ray emission and the nonthermal X-ray emission appears likely. Different interpretations of the γ-ray signal from R136 are discussed.
|
[
1833,
732,
903,
628
] |
[
"young star clusters",
"massive stars",
"large magellanic cloud",
"gamma-ray astronomy"
] |
2023ApJ...953...93S
|
Observational Properties of a Bright Type lax SN 2018cni and a Faint Type Iax SN 2020kyg
|
We present the optical photometric and spectroscopic analysis of two Type Iax supernovae (SNe), 2018cni and 2020kyg. SN 2018cni is a bright Type Iax SN (M <SUB> V,peak</SUB> = -17.81 ± 0.21 mag), whereas SN 2020kyg (M <SUB> V,peak</SUB> = -14.52 ± 0.21 mag) is a faint one. We derive <SUP>56</SUP>Ni mass of 0.07 and 0.002 M <SUB>⊙ </SUB>and ejecta mass of 0.48 and 0.14 M <SUB>⊙</SUB> for SNe 2018cni and 2020kyg, respectively. A combined study of the bright and faint Type Iax SNe in R/r-band reveals that the brighter objects tend to have a longer rise time. However, the correlation between the peak luminosity and decline rate shows that bright and faint Type Iax SNe exhibit distinct behavior. Comparison with standard deflagration models suggests that SN 2018cni is consistent with the deflagration of a CO white dwarf, whereas the properties of SN 2020kyg can be better explained by the deflagration of a hybrid CONe white dwarf. The spectral features of both the SNe point to the presence of similar chemical species but with different mass fractions. Our spectral modeling indicates stratification at the outer layers and mixed inner ejecta for both of the SNe.
|
[
1668
] |
[
"supernovae"
] |
2022ApJ...930...15D
|
SpeX Near-infrared Spectroscopic Extinction Curves in the Milky Way
|
Interstellar dust extinction curves provide valuable information about dust properties, including the composition and size of the dust grains, and are essential to correct observations for the effects of interstellar dust. In this work, we measure a representative sample of near-infrared (NIR; 0.8-5.5 μm) spectroscopic extinction curves for the first time, enabling us to investigate the extinction at wavelengths where it is usually only measured in broad photometric bands. We use IRTF/SpeX spectra of a sample of reddened and comparison stars to measure 15 extinction curves with the pair method. Our sample spans A(V) values from 0.78 to 5.65 and R(V) values from 2.43 to 5.33. We confirm that the NIR extinction curves are well fit by a power law, with indices and amplitudes differing from sight line to sight line. Our average diffuse NIR extinction curve can be represented by a single power law with index α = 1.7, but because of the sight line-to-sight line variations, the shape of any average curve will depend on the parental sample. We find that most of the variation in our sample can be linked to the ratio of total-to-selective extinction R(V), a rough measurement of the average dust grain size. Two sight lines in our sample clearly show the ice extinction feature at 3 μm, which can be fitted by a modified Drude profile. We find tentative ice detections with slightly over 3σ significance in two other sight lines. In our average diffuse extinction curve, we measure a 3σ upper limit of A(ice)/A(V) = 0.0021 for this ice feature.
|
[
836,
837,
505,
1376,
841,
853,
847,
1093,
1377,
1054
] |
[
"interstellar dust",
"interstellar dust extinction",
"extinction",
"reddened stars",
"interstellar extinction",
"interstellar reddening",
"interstellar medium",
"near infrared astronomy",
"reddening law",
"milky way galaxy"
] |
2021RNAAS...5...76J
|
Identification of a Low-mass Companion to the White Dwarf SDSS J131730.84+483332.7
|
We present the discovery of 2MASS J13173072+4833343, a low-mass stellar companion to the ∼5.5 Gyr old white dwarf SDSS J131730.85+483332.8. This companion was discovered through the Backyard Worlds: Planet 9 citizen science collaboration. We obtained a near-infrared spectrum of the companion and determined a spectral type of M8.5. Using the cooling age of the white dwarf, we determined that the stellar companion has a mass of ${0.077}_{-0.017}^{+0.005}$ M<SUB>⊙</SUB>, or ${80.2}_{-1.8}^{+0.5}$ M<SUB>Jup</SUB>, near the substellar boundary.
|
[
1648,
154
] |
[
"substellar companion stars",
"binary stars"
] |
2020ApJ...888..109J
|
HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z = 3.794
|
We report on the Hubble Space Telescope (HST) detection of the Lyman-continuum (LyC) radiation emitted by a galaxy at redshift z = 3.794 dubbed Ion1. The LyC from Ion1 is detected at 820-890 Å with HST WFC3/UVIS in the F410M band (m<SUB>410</SUB> = 27.60 ± 0.36 m<SUB>AB</SUB>, peak signal-to-noise ratio (S/N) = 4.17 in an r = 0"12 aperture) and 700-830 Å with the Very Large Telescope (VLT)/VIMOS in the U band (m<SUB>U</SUB> = 27.84 ± 0.19 m<SUB>AB</SUB>, peak S/N = 6.7 with an r = 0"6 aperture). A 20 hr VLT/VIMOS spectrum shows low- and high-ionization interstellar metal absorption lines and the P Cygni profile of C IV and Lyα in absorption. The latter spectral feature differs from what observed in known LyC emitters, which show strong Lyα emission. An HST far-UV color map reveals that the LyC emission escapes from a region of the galaxy that is bluer than the rest. The F410M image shows that the centroid of the LyC emission is offset from the centroid of the nonionizing UV emission by 0"12 ± 0"03, corresponding to 0.85 ± 0.21 kpc, and that its morphology is likely moderately resolved. These morphological characteristics favor a scenario where the LyC photons produced by massive stars escape from low H I column density "cavities" in the interstellar medium. We also collect the VIMOS U-band images of 107 Lyman-break galaxies at 3.40 < z<SUB>spec</SUB> < 3.95, I.e., sampling the LyC, and stack them with inverse-variance weights. No LyC emission is detected in the stacked image, resulting in a 32.5 m<SUB>AB</SUB> flux limit (1σ) and an upper limit of absolute LyC escape fraction f<SUB>esc</SUB><SUP>abs</SUP> ≤ 0.63%.
|
[
1383,
734,
506
] |
[
"reionization",
"high-redshift galaxies",
"extragalactic astronomy"
] |
2022ApJ...929..103T
|
SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation
|
We report on the presence of numerous tiny bright dots in and around an emerging flux region (an X-ray/coronal bright point) observed with SolO's EUI/HRI<SUB>EUV</SUB> in 174 Å. These dots are roundish and have a diameter of 675 ± 300 km, a lifetime of 50 ± 35 s, and an intensity enhancement of 30% ± 10% above their immediate surroundings. About half of the dots remain isolated during their evolution and move randomly and slowly (<10 km s<SUP>-1</SUP>). The other half show extensions, appearing as a small loop or surge/jet, with intensity propagations below 30 km s<SUP>-1</SUP>. Many of the bigger and brighter HRI<SUB>EUV</SUB> dots are discernible in the SDO/AIA 171 Å channel, have significant emissivity in the temperature range of 1-2 MK, and are often located at polarity inversion lines observed in SDO/HMI LOS magnetograms. Although not as pervasive as in observations, a Bifrost MHD simulation of an emerging flux region does show dots in synthetic Fe IX/X images. These dots in the simulation show distinct Doppler signatures-blueshifts and redshifts coexist, or a redshift of the order of 10 km s<SUP>-1</SUP> is followed by a blueshift of similar or higher magnitude. The synthetic images of O V/VI and Si IV lines, which represent transition region radiation, also show the dots that are observed in Fe IX/X images, often expanded in size, or extended as a loop, and always with stronger Doppler velocities (up to 100 km s<SUP>-1</SUP>) than that in Fe IX/X lines. Our observation and simulation results, together with the field geometry of dots in the simulation, suggest that most dots in emerging flux regions form in the lower solar atmosphere (at ≈ 1 Mm) by magnetic reconnection between emerging and preexisting/emerged magnetic field. Some dots might be manifestations of magnetoacoustic shocks through the line formation region of Fe IX/X emission.
|
[
1483,
2000,
1504,
1493,
1532,
312,
1812
] |
[
"solar corona",
"solar magnetic flux emergence",
"solar magnetic reconnection",
"solar extreme ultraviolet emission",
"solar transition region",
"solar coronal transients",
"x-ray bright point"
] |
2023ApJ...949...90L
|
Revisiting the Chandra Observation on the Region of PSR J1809-193: Indication of the Existence of an X-Ray Halo and Implication for the Origin of HESS J1809-193
|
HESS J1809-193 is an extended TeV γ-ray source and the origin of its γ-ray emission remains ambiguous. The pulsar wind nebula (PWN) of PSR J1J1809-193 lying inside the extended γ-ray emission is a possible candidate. Powered by the central pulsar, ultrarelativistic electrons in the PWN can produce radio to X-ray emission through synchrotron and γ-ray emission by inverse Compton (IC) scattering. To check whether this PWN is the counterpart of HESS J1809-193, we analyzed the Chandra X-ray radial intensity profile and spectral index profile of this PWN. We then adopted a one-zone isotropic diffusion model to fit the keV and TeV data. We found diffuse nonthermal X-ray emission extending beyond the PWN, which is likely an X-ray halo radiated by escaping electron/positron pairs from the PWN. A relatively strong magnetic field of ~20 μG is required to explain the spatial evolution of the X-ray spectrum (i.e., the significant softening of the spectrum with increasing distance from the pulsar), which, however, would suppress the IC radiation of pairs. Our result implies that a hadronic component may be needed to explain HESS J1809-193.
|
[
739,
2215,
1810,
633,
1119
] |
[
"high energy astrophysics",
"pulsar wind nebulae",
"x-ray astronomy",
"gamma-ray sources",
"non-thermal radiation sources"
] |
2020ApJ...904....2G
|
The Clustering of Submillimeter Galaxies Detected with ALMA
|
Previous studies measuring the clustering of submillimeter galaxies (SMGs) have based their measurements on single-dish-detected sources, finding evidence for strong clustering. However, ALMA has revealed that, due to the coarse angular resolution of these instruments, single-dish sources can be composed of multiple sources. This implies that the clustering inferred from single-dish surveys may be overestimated. Here, we measure the clustering of SMGs based on the ALESS survey, an ALMA follow-up of sources previously identified in the LABOCA ECDFS Submillimeter Survey (LESS). We present a method to measure the clustering of ALMA sources that have been previously identified using single-dish telescopes, based on forward modeling both the single-dish and the ALMA observations. We constrain upper limits for the median mass of halos hosting SMGs at 1 < z < 3, finding ${M}_{\mathrm{halo}}\leqslant 2.4\times {10}^{12}\,{M}_{\odot }$ for SMGs with flux densities ${S}_{870}\geqslant 4.0\,$ mJy, which is at least ${3.8}_{-2.6}^{+3.8}$ times lower than the mass inferred based on the clustering of the LESS sources alone. This suggests that the strength of SMG clustering based on single-dish observations was overestimated, and therefore SMGs might be hosted by dark matter halos less massive than has previously been estimated. By extrapolating our models down to flux densities of ${S}_{870}\geqslant 1.2\,\,$ mJy, we find that such SMGs inhabit halos with median mass ${M}_{\mathrm{halo}}\leqslant 3.2\times {10}^{11}\,{M}_{\odot }$ . We conclude that only the brightest ( ${S}_{870}\gtrsim 5-6\,\,$ mJy) SMGs would trace massive structures at z ∼ 2 and only SMGs with ${S}_{870}\gtrsim 6\,\,$ mJy may be connected to massive local elliptical galaxies, quasars at intermediate redshifts, and high-redshift star-forming galaxies, whereas fainter SMGs are unlikely linked to these populations.
|
[
594,
734,
1570,
1647,
902,
1908,
1859
] |
[
"galaxy evolution",
"high-redshift galaxies",
"starburst galaxies",
"submillimeter astronomy",
"large-scale structure of the universe",
"clustering",
"astronomy data modeling"
] |
2020ApJS..249...12B
|
Identification of Single Spectral Lines through Supervised Machine Learning in a Large HST Survey (WISP): A Pilot Study for Euclid and WFIRST
|
Future surveys focusing on understanding the nature of dark energy (e.g., Euclid and WFIRST) will cover large fractions of the extragalactic sky in near-IR slitless spectroscopy. These surveys will detect a large number of galaxies that will have only one emission line in the covered spectral range. In order to maximize the scientific return of these missions, it is imperative that single emission lines are correctly identified. Using a supervised machine-learning approach, we classified a sample of single emission lines extracted from the WFC3 IR Spectroscopic Parallel survey, one of the closest existing analogs to future slitless surveys. Our automatic software integrates a spectral energy distribution (SED)-fitting strategy with additional independent sources of information. We calibrated it and tested it on a "gold" sample of securely identified objects with multiple lines detected. The algorithm correctly classifies real emission lines with an accuracy of 82.6%, whereas the accuracy of the SED-fitting technique alone is low (∼50%) due to the limited amount of photometric data available (≤6 bands). While not specifically designed for the Euclid and WFIRST surveys, the algorithm represents an important precursor of similar algorithms to be used in these future missions.
|
[
1558,
1883,
1901,
2073,
1378
] |
[
"spectroscopy",
"algorithms",
"maximum likelihood estimation",
"spectral line identification",
"redshift surveys"
] |
2023ApJ...954..115K
|
The Baryonic Content of Galaxies Mapped by MaNGA and the Gas Around Them
|
We analyze the cool gas in and around 14 nearby galaxies (at z < 0.1) mapped with the Sloan Digital Sky Survey IV MaNGA survey by measuring absorption lines produced by gas in spectra of background quasars/active galactic nuclei at impact parameters of 0-25 effective radii from the galactic centers. Using Hubble Space Telescope/Cosmic Origins Spectrograph, we detect absorption at the galactic redshift and measure or constrain column densities of neutral (H I, N I, O I, and Ar I), low-ionization (Si II, S II, C II, N II, and Fe II), and high-ionization (Si III, Fe III, N V, and O VI) species for 11 galaxies. We derive the ionization parameter and ionization-corrected metallicity using CLOUDY photoionization models. The H I column density ranges from ~10<SUP>13</SUP> to ~10<SUP>20</SUP> cm<SUP>-2</SUP> and decreases with impact parameter for r ≳ R <SUB> e </SUB>. Galaxies with higher stellar mass have weaker H I absorption. Comparing absorption velocities with MaNGA radial velocity maps of ionized gas line emissions in galactic disks, we find that the neutral gas seen in absorption corotates with the disk out to ~10 R <SUB> e </SUB>. Sight lines with lower elevation angles show lower metallicities, consistent with the metallicity gradient in the disk derived from MaNGA maps. Higher-elevation angle sight lines show higher ionization, lower H I column density, supersolar metallicity, and velocities consistent with the direction of galactic outflow. Our data offer the first detailed comparisons of circumgalactic medium (CGM) properties (kinematics and metallicity) with extrapolations of detailed galaxy maps from integral field spectroscopy; similar studies for larger samples are needed to more fully understand how galaxies interact with their CGM.
|
[
594,
1569,
1317,
847,
1146
] |
[
"galaxy evolution",
"star formation",
"quasar absorption line spectroscopy",
"interstellar medium",
"observational cosmology"
] |
2024AJ....167..138V
|
Orbital and Absolute Magnitude Distribution of Jupiter Trojans
|
Jupiter Trojans (JTs) librate about the Lagrangian stationary centers L4 and L5 associated with this planet on typically small-eccentricity and moderate-inclination heliocentric orbits. The physical and orbital properties of JTs provide important clues about the dynamical evolution of the giant planets in the early solar system, as well as populations of planetesimals in their source regions. Here we use decade-long observations from the Catalina Sky Survey (station G96) to determine the bias-corrected orbital and magnitude distributions of JTs. We distinguish the background JT population, filling smoothly the long-term stable orbital zone about L4 and L5 points and collisional families. We find that the cumulative magnitude distribution of JTs (the background population in our case) has a steep slope for H ≤ 9, followed by a moderately shallow slope until H ≃ 14.5, beyond which the distribution becomes even shallower. At H = 15 we find a local power-law exponent 0.38 ± 0.01. We confirm the asymmetry between the magnitude-limited background populations in L4 and L5 clouds characterized by a ratio 1.45 ± 0.05 for H < 15. Our analysis suggests an asymmetry in the inclination distribution of JTs, with the L4 population being tighter and the L5 population being broader. We also provide a new catalog of the synthetic proper elements for JTs with an updated identification of statistically robust families (9 at L4, and 4 at L5). The previously known Ennomos family is found to consist of two overlapping Deiphobus and Ennomos families.
|
[
1529,
1469
] |
[
"solar system astronomy",
"small solar system bodies"
] |
2020ApJS..249...33K
|
Molecular Cloud Cores with a High Deuterium Fraction: Nobeyama Single-pointing Survey
|
We present the results of a single-pointing survey of 207 dense cores embedded in Planck Galactic Cold Clumps distributed in five different environments (λ Orionis, Orion A, Orion B, the Galactic plane, and high latitudes) to identify dense cores on the verge of star formation for the study of the initial conditions of star formation. We observed these cores in eight molecular lines at 76-94 GHz using the Nobeyama 45 m telescope. We find that early-type molecules (e.g., CCS) have low detection rates and that late-type molecules (e.g., N<SUB>2</SUB>H<SUP>+</SUP> and c-C<SUB>3</SUB>H<SUB>2</SUB>) and deuterated molecules (e.g., N<SUB>2</SUB>D<SUP>+</SUP> and DNC) have high detection rates, suggesting that most of the cores are chemically evolved. The deuterium fraction (D/H) is found to decrease with increasing distance, indicating that it suffers from differential beam dilution between the D/H pair of lines for distant cores (>1 kpc). For λ Orionis, Orion A, and Orion B located at similar distances, D/H is not significantly different, suggesting that there is no systematic difference in the observed chemical properties among these three regions. We identify at least eight high-D/H cores in the Orion region and two at high latitudes, which are most likely to be close to the onset of star formation. There is no clear evidence of the evolutionary change in turbulence during the starless phase, suggesting that the dissipation of turbulence is not a major mechanism for the beginning of star formation as judged from observations with a beam size of 0.04 pc.
|
[
258,
849,
75,
1569
] |
[
"earth's clouds",
"interstellar molecules",
"astrochemistry",
"star formation"
] |
2020ApJ...899...64A
|
Environmental Impact on Star-forming Galaxies in a z ∼ 0.9 Cluster during the Course of Galaxy Accretion
|
Galaxies change their properties as they assemble into clusters. In order to understand the physics behind that, we need to go back in time and observe directly what is occurring in galaxies as they fall into a cluster. We have conducted a narrowband and J-band imaging survey on a cluster CL1604-D at z = 0.923 using a new infrared instrument SWIMS installed at the Subaru Telescope. The narrowband filter, NB1261, matches to Hα emission from the cluster at z = 0.923. Combined with a wide range of existing data from various surveys, we have investigated galaxy properties in and around this cluster in great detail. We have identified 27 Hα emitters associated with the cluster. They have significant overlap with MIPS $24\,\mu {\rm{m}}$ sources and are located exclusively in the star-forming regime on the rest-frame UVJ diagram. We have identified two groups of galaxies near the cluster in the 2D spatial distribution and the phase-space diagram, which are likely to be in-falling to the cluster main body. We have compared various physical properties of star-forming galaxies, such as specific star formation rates (burstiness) and morphologies (merger) as a function of environment, cluster center, older group, younger group, and the field. As a result, a global picture has emerged on how the galaxy properties are altered as they assemble into a denser region. This includes the occurrence of mergers, enhancement of star formation activity, excursion to the dusty starburst phase, and eventual quenching to a passive phase.
|
[
584,
563,
594
] |
[
"galaxy clusters",
"galactic and extragalactic astronomy",
"galaxy evolution"
] |
2023ApJ...945..106P
|
A Deep-learning Anomaly-detection Method to Identify Gamma-Ray Bursts in the Ratemeters of the AGILE Anticoincidence System
|
Astro-rivelatore Gamma a Immagini Leggero (AGILE) is a space mission launched in 2007 to study X-ray and gamma-ray astronomy. The AGILE team developed real-time analysis pipelines to detect transient phenomena such as gamma-ray bursts (GRBs) and react to external science alerts received by other facilities. The AGILE anticoincidence system (ACS) comprises five panels surrounding the AGILE detectors to reject background-charged particles. It can also detect hard X-ray photons in the energy range 50-200 keV. The ACS data acquisition produces a time series for each panel. The time series are merged into a single multivariate time series (MTS). We present a new deep-learning model for the detection of GRBs in the ACS data using an anomaly detection technique. The model is implemented with a convolutional neural network autoencoder architecture trained in an unsupervised manner, using a data set of MTSs randomly extracted from the AGILE ACS data. The reconstruction error of the autoencoder is used as the anomaly score to classify the MTS. We calculated the associated p-value distribution, using more than 10<SUP>7</SUP> background-only MTSs, to define the statistical significance of the detections. We evaluate the trained model with a list of GRBs reported by the GRBWeb catalog. The results confirm the model's capabilities to detect GRBs in the ACS data. We will implement this method in the AGILE real-time analysis pipeline.
|
[
1916,
629,
628,
630,
1938
] |
[
"time series analysis",
"gamma-ray bursts",
"gamma-ray astronomy",
"gamma-ray detectors",
"convolutional neural networks"
] |
2022ApJ...936...43H
|
Overview of the Remote Sensing Observations from PSP Solar Encounter 10 with Perihelion at 13.3 R <SUB>⊙</SUB>
|
The closest perihelion pass of Parker Solar Probe (PSP), so far, occurred between 2021 November 16 and 26 and reached ~13.29 R <SUB>☉</SUB> from Sun center. This pass resulted in very unique observations of the solar corona by the Wide-field Instrument for Solar PRobe (WISPR). WISPR observed at least 10 coronal mass ejections (CMEs), some of which were so close that the structures appear distorted. All of the CMEs appeared to have a magnetic flux rope (MFR) structure, and most were oriented such that the view was along the axis orientation, revealing very complex interiors. Two CMEs had a small MFR develop in the interior, with a bright circular boundary surrounding a very dark interior. Trailing the larger CMEs were substantial outflows of small blobs and flux-rope-like structures within striated ribbons, lasting for many hours. When the heliospheric plasma sheet was inclined, as it was during the days around perihelion on 2021 November 21, the outflow was over a very wide latitude range. One CME was overtaken by a faster one, with a resultant compression of the rear of the leading CME and an unusual expansion in the trailing CME. The small Thomson surface creates brightness variations of structures as they pass through the field of view. In addition to this dynamic activity, a brightness band from excess dust along the orbit of asteroid/comet 3200 Phaethon is also seen for several days.
|
[
310,
1534,
2042,
1486
] |
[
"solar coronal mass ejections",
"solar wind",
"solar k corona",
"solar coronal streamers"
] |
2021ApJ...907...16B
|
Alfvénic Perturbations in a Sunspot Chromosphere Linked to Fractionated Plasma in the Corona
|
In this study, we investigate the spatial distribution of highly varying plasma composition around one of the largest sunspots of solar cycle 24. Observations of the photosphere, chromosphere, and corona are brought together with magnetic field modeling of the sunspot in order to probe the conditions that regulate the degree of plasma fractionation within loop populations of differing connectivities. We find that, in the coronal magnetic field above the sunspot umbra, the plasma has photospheric composition. Coronal loops rooted in the penumbra contain fractionated plasma, with the highest levels observed in the loops that connect within the active region. Tracing field lines from regions of fractionated plasma in the corona to locations of Alfvénic fluctuations detected in the chromosphere shows that they are magnetically linked. These results indicate a connection between sunspot chromospheric activity and observable changes in coronal plasma composition.
|
[
1653,
994,
1975,
1479,
1483
] |
[
"sunspots",
"magnetic fields",
"solar active region magnetic fields",
"solar chromosphere",
"solar corona"
] |
2022ApJ...934..130Z
|
The Star-forming Main Sequence of the Host Galaxies of Low-redshift Quasars
|
We investigate the star-forming main sequence of the host galaxies of a large, well-defined sample of 453 redshift ~0.3 quasars with previously available star formation rates by deriving stellar masses from modeling their broadband (grizy) spectral energy distribution. We perform two-dimensional, simultaneous, multi-filter decomposition of Pan-STARRS1 3π Steradian Survey images to disentangle the active galactic nucleus (AGN) from its host galaxy, by explicitly considering, for the first time, the wavelength variation of galaxy structures. We quantify the Sérsic profiles and sizes of the host galaxies from mock AGNs generated from both real and idealized galaxies. Detailed morphological classifications of the calibration galaxy sample using Hubble Space Telescope images enable us to estimate crude morphological types of the quasars. Although the majority (~60%) of the quasars are hosted by bulge-dominated, early-type galaxies, a substantial fraction (~40%) reside in disk-dominated, late-type galaxies, suggesting that at least in these systems major mergers have not played a significant role in regulating their AGN activity, in agreement with recent simulations and observations of nearby quasars. The vast majority (~90%) of the quasars have star formation rates that place them on or above the galaxy star-forming main sequence, with more rapidly accreting AGNs displaced further above the main sequence. Quasar host galaxies generally follow the stellar mass-size relation defined by inactive galaxies, both for late-type and early-type systems, but roughly 1/3 of the population has smaller sizes at a given stellar mass, reminiscent of compact star-forming galaxies at higher redshift.
|
[
16,
594,
622,
1663,
2017,
1319
] |
[
"active galactic nuclei",
"galaxy evolution",
"galaxy structure",
"supermassive black holes",
"agn host galaxies",
"quasars"
] |
2022ApJ...933L..36J
|
MUSSES2020J: The Earliest Discovery of a Fast Blue Ultraluminous Transient at Redshift 1.063
|
In this Letter, we report the discovery of an ultraluminous fast-evolving transient in rest-frame UV wavelengths, MUSSES2020J, soon after its occurrence by using the Hyper Suprime-Cam (HSC) mounted on the 8.2 m Subaru telescope. The rise time of about 5 days with an extremely high UV peak luminosity shares similarities to a handful of fast blue optical transients whose peak luminosities are comparable with the most luminous supernovae while their timescales are significantly shorter (hereafter "fast blue ultraluminous transient," FBUT). In addition, MUSSES2020J is located near the center of a normal low-mass galaxy at a redshift of 1.063, suggesting a possible connection between the energy source of MUSSES2020J and the central part of the host galaxy. Possible physical mechanisms powering this extreme transient such as a wind-driven tidal disruption event and an interaction between supernova and circumstellar material are qualitatively discussed based on the first multiband early-phase light curve of FBUTs, although whether the scenarios can quantitatively explain the early photometric behavior of MUSSES2020J requires systematical theoretical investigations. Thanks to the ultrahigh luminosity in UV and blue optical wavelengths of these extreme transients, a promising number of FBUTs from the local to the high-z universe can be discovered through deep wide-field optical surveys in the near future.
|
[
1957,
1851,
1854,
2109,
288,
1800,
1169
] |
[
"transient detection",
"transient sources",
"ultraviolet transient sources",
"time domain astronomy",
"compact objects",
"wide-field telescopes",
"optical observation"
] |
2021ApJ...912...26C
|
X-Ray Spectroscopy in the Microcalorimeter Era. III. Line Formation under Case A, Case B, Case C, and Case D in H- and He-like Iron for a Photoionized Cloud
|
Future microcalorimeter X-ray observations will resolve spectral features in unmatched detail. Understanding of line formation processes in X-rays deserves much attention. The purpose of this paper is to discuss such processes in the presence of a photoionizing source. Line formation processes in one- and two-electron species are broadly categorized into four cases. Case A occurs when the Lyman line optical depths are very small and photoexcitation does not occur. Line photons escape the cloud without any scattering. Case B occurs when the Lyman line optical depths are large enough for photons to undergo multiple scatterings. Case C occurs when a broadband continuum source strikes an optically thin cloud. The Lyman lines are enhanced by induced radiative excitation of the atoms/ions by continuum photons, also known as continuum pumping. A fourth, less studied scenario, where the Case B spectrum is enhanced by continuum pumping, is called Case D. Here, we establish the mathematical foundation of Cases A, B, C, and D in an irradiated cloud with Cloudy. We also show the total X-ray emission spectrum for all four cases within the energy range 0.1-10 keV at the resolving power of XRISM around 6 keV. Additionally, we show that the combined effect of electron scattering and partial blockage of continuum pumping reduces the resonance line intensities. Such reduction increases with column density and can serve as an important tool to measure the column density/optical depth of the cloud.
|
[
1810,
2060
] |
[
"x-ray astronomy",
"photoionization"
] |
2020ApJ...903....6M
|
Fast Iterative Techniques for Polarized Radiative Transfer in Spherically Symmetric Moving Media
|
For a more precise modeling of polarized spectral lines formed in extended and expanding stellar atmospheres, the solution of the radiative transfer equation for the Stokes vectors must be obtained in a spherical geometry rather than in a planar geometry. In this paper, we present the modern iterative techniques based on operator perturbation to solve the spherically symmetric polarized radiative transfer equation with velocity fields. We consider scattering on a two-level atom and account for partial frequency redistribution. An accurate numerical solution to such problems requires the use of spatial grids with higher resolution. Consequently, Jacobi-based methods lead to slower convergence rate. The convergence rate can be improved by a factor of 2 or more when fast iterative schemes based on Gauss-Seidel (GS) and successive overrelaxation (SOR) methods are used over the Jacobi-based method. Here we present the Jacobi, GS, and SOR iterative techniques for solving the abovementioned problem, and discuss their convergence behavior.
|
[
1477,
1336,
1973,
1965,
1967
] |
[
"solar atmosphere",
"radiative transfer equation",
"spectropolarimetry",
"computational methods",
"radiative transfer simulations"
] |
2022ApJ...930...31B
|
Characterization of Supernovae Based on the Spectral-Temporal Energy Distribution: Two Possible SN Ib Subtypes
|
A quantitative data-driven comparison among supernovae (SNe) based on their spectral time series combined with multiband photometry is presented. We use an unsupervised random forest algorithm as a metric on a set of 82 well-documented SNe representing all the main spectroscopic types, in order to embed these in an abstract metric space reflecting shared correlations between the objects. We visualize the resulting metric space in 3D, revealing strong agreement with the current spectroscopic classification scheme. The embedding splits Type Ib supernovae into two groups, with one subgroup exhibiting broader, less prominent, higher-velocity lines than the other, possibly suggesting a new SN Ib subclass is required. The method could be to classify newly discovered SNe according to their distance from known event groups, or ultimately to devise a new, spectral-temporal classification scheme. Such an embedding could also depend on hidden parameters that may perhaps be physically interpretable.
|
[
1668,
1729,
1935,
1907
] |
[
"supernovae",
"type ib supernovae",
"random forests",
"classification"
] |
2021ApJ...921...46B
|
Evidence for Coronal Temperature Variation in Seyfert 2 ESO 103-035 Using NuSTAR Observations
|
We report flux-resolved spectroscopic analysis of the active galactic nucleus (AGN) ESO 103-035 using NuSTAR observations. Following an earlier work, we fit the spectra using a thermal Comptonization model with a relativistic reflection component to obtain estimates of the coronal temperature for two flux levels. The coronal temperature was found to increase from ${24.0}_{-3.4}^{+6.8}$ to ${55.3}_{-7.2}^{+54.6}\,\mathrm{keV}$ (errors at the 1σ confidence level) as the flux increased from 9.8 to 11.9 × 10<SUP>-11</SUP> erg cm<SUP>-2</SUP> s<SUP>-1</SUP> in the 3-78 keV band. A marginal variation in the high energy photon index allows for both a nonvarying optical depth and for the optical depth to have varied by a factor of ~2. This is in contrast to a previous work on NuSTAR flux-resolved spectroscopy of the AGN, Ark 564, where the temperature was found to decrease with flux along with a 10% variation in the optical depth. The results may be understood in a framework where AGN variability is either dominated by coronal heating variation leading to a correlated increase of temperature with flux or the opposite effect being seen when the variability is dominated by changes in the seed photon flux.
|
[
17,
159,
2035,
1447,
739
] |
[
"active galaxies",
"black hole physics",
"x-ray active galactic nuclei",
"seyfert galaxies",
"high energy astrophysics"
] |
2022ApJ...933...84F
|
LoVoCCS. I. Survey Introduction, Data Processing Pipeline, and Early Science Results
|
We present the Local Volume Complete Cluster Survey (LoVoCCS; we pronounce it as "low-vox" or "law-vox," with stress on the second syllable), an NSF's National Optical-Infrared Astronomy Research Laboratory survey program that uses the Dark Energy Camera to map the dark matter distribution and galaxy population in 107 nearby (0.03 < z < 0.12) X-ray luminous ([0.1-2.4 keV] L <SUB>X500</SUB> > 10<SUP>44</SUP> erg s<SUP>-1</SUP>) galaxy clusters that are not obscured by the Milky Way. The survey will reach Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) Year 1-2 depth (for galaxies r = 24.5, i = 24.0, signal-to-noise ratio (S/N) > 20; u = 24.7, g = 25.3, z = 23.8, S/N > 10) and conclude in ~2023 (coincident with the beginning of LSST science operations), and will serve as a zeroth-year template for LSST transient studies. We process the data using the LSST Science Pipelines that include state-of-the-art algorithms and analyze the results using our own pipelines, and therefore the catalogs and analysis tools will be compatible with the LSST. We demonstrate the use and performance of our pipeline using three X-ray luminous and observation-time complete LoVoCCS clusters: A3911, A3921, and A85. A3911 and A3921 have not been well studied previously by weak lensing, and we obtain similar lensing analysis results for A85 to previous studies. (We mainly use A3911 to show our pipeline and give more examples in the Appendix.)
|
[
1797,
1858,
1671,
584,
1146,
353
] |
[
"weak gravitational lensing",
"astronomy data analysis",
"surveys",
"galaxy clusters",
"observational cosmology",
"dark matter"
] |
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