adsabs/SciX_UAT_keywords huggingface dataset:
Molecular Gas Distribution Perpendicular to the Galactic Plane

We use the ∼370 deg2 data from the MWISP CO survey to study the vertical distribution of the molecular clouds (MCs) toward the tangent points in the region of l = [+16°, +52°] and ∣b∣ < 5°1. We find that the molecular disk consists of two components with a layer thickness (FWHM) of ∼85 pc and ∼280 pc, respectively. In the inner Galaxy, the molecular mass in the thin disk is dominant, while the molecular mass traced by the discrete MCs with weak CO emission in the thick disk is probably ≲10% of the whole molecular disk. For the CO gas in the thick disk, we identified 1055 high-z MCs that are ≳100 pc from the Galactic plane. However, only a few samples (i.e., 32 MCs or 3%) are located in the ∣z∣ ≳ 360 pc region. Typically, the discrete MCs of the thick-disk population have a median peak temperature of 2.1 K, a median velocity dispersion of 0.8 km s-1, and a median effective radius of 2.5 pc. Assuming a constant value of XCO = 2 × 1020 cm-2(K km s-1)-1, the median surface density of these MCs is 6.8 M⊙ pc-2, indicating very faint CO emission for the high-z gas. The cloud-cloud velocity dispersion is 4.9 ± 1.3 km s-1 and a linear variation with a slope of ∼-0.4 km s-1 kpc-1 is obtained in the region of RGC = 2.2-6.4 kpc. Assuming that these clouds are supported by their turbulent motions against the gravitational pull of the disk, a model of ρ0(R) = 1.28 M⊙ pc-3 ${e}^{-\displaystyle \frac{R}{3.2\mathrm{kpc}}}$ <!-- --> can be used to describe the distribution of the total mass density in the Galactic midplane.

Keywords: interstellar medium; molecular clouds; surveys; milky way disk; interstellar dynamics; stellar-interstellar interactions
On the Single-event-based Identification of Primordial Black Hole Mergers at Cosmological Distances

The existence of primordial black holes (PBHs), which may form from the collapse of matter overdensities shortly after the Big Bang, is still under debate. Among the potential signatures of PBHs are gravitational waves (GWs) emitted from binary black hole (BBH) mergers at redshifts z ≳ 30, where the formation of astrophysical black holes is unlikely. Future ground-based GW detectors, the Cosmic Explorer and Einstein Telescope, will be able to observe equal-mass BBH mergers with total mass of ${ \mathcal O }(10\mbox{--}100)\,{M}_{\odot }$ at such distances. In this work, we investigate whether the redshift measurement of a single BBH source can be precise enough to establish its primordial origin. We simulate BBHs of different masses, mass ratios and orbital orientations. We show that for BBHs with total masses between 20 M ⊙ and 40 M ⊙ merging at z ≥ 40, one can infer z > 30 at up to 97% credibility, with a network of one Einstein Telescope, one 40 km Cosmic Explorer in the US, and one 20 km Cosmic Explorer in Australia. This number reduces to 94% with a smaller network made of one Einstein Telescope and one 40 km Cosmic Explorer in the US. We also analyze how the measurement depends on the Bayesian priors used in the analysis and verify that priors that strongly favor the wrong model yield smaller Bayesian evidences.

Keywords: gravitational waves; primordial black holes; astrophysical black holes; stellar mass black holes
Effect of Dust Rotational Disruption by Radiative Torques and Implications for the F-corona Decrease Revealed by the Parker Solar Probe

The first-year results from the Parker Solar Probe (PSP) reveal a gradual decrease of F-coronal dust from distances of D = 0.166-0.336 au (or the inner elongations of ~9.22-18.69 R⊙) to the Sun. Such an F-corona decrease cannot be explained by the dust sublimation scenario of the popular silicate composition that implies a dust-free boundary zone at heliocentric radius R ≲ 4-5 R⊙, but it may be explained by appealing to various dust compositions with different sublimation fronts. In this paper, we present an additional explanation for the F-corona decrease using our newly introduced mechanism of dust destruction, the so-called Radiative Torque Disruption (RATD) mechanism. We demonstrate that the RATD rapidly breaks large grains into nanoparticles so that they can be efficiently destroyed by nonthermal sputtering induced by the bombardment of energetic protons from slow solar winds, which extends the dust-free zone established by thermal sublimation to Rdfz ~ 8 R⊙. Beyond this extended dust-free zone, we find that the dust mass decreases gradually from R ~ 42 R⊙ toward the Sun due to partial removal of nanodust by nonthermal sputtering. The joint effect of the RATD and nonthermal sputtering can successfully reproduce the gradual decrease of the F-corona between 19 and 9 R⊙ observed by the PSP. Finally, the RATD mechanism can efficiently produce nanoparticles usually observed in the inner solar system.

Keywords: solar f corona; interstellar dust; interplanetary dust; circumstellar dust
Multicolor Variability of Young Stars in the Lagoon Nebula: Driving Causes and Intrinsic Timescales

Space observatories have provided unprecedented depictions of the many variability behaviors typical of low-mass, young stars. However, those studies have so far largely omitted more massive objects (~2 M⊙ to 4-5 M⊙) and were limited by the absence of simultaneous, multiwavelength information. We present a new study of young star variability in the ~1-2 Myr old, massive Lagoon Nebula region. Our sample encompasses 278 young, late B to K-type stars, monitored with Kepler/K2. Auxiliary u, g, r, i, Hα time-series photometry, simultaneous with K2, was acquired at the Paranal Observatory. We employed this comprehensive data set and archival infrared photometry to determine individual stellar parameters, assess the presence of circumstellar disks, and tie the variability behaviors to inner disk dynamics. We found significant mass-dependent trends in variability properties, with B/A stars displaying substantially reduced levels of variability compared to G/K stars for any light-curve morphology. These properties suggest different magnetic field structures at the surface of early-type and later-type stars. We also detected a dearth of some disk-driven variability behaviors, particularly dippers, among stars earlier than G. This indicates that their higher surface temperatures and more chaotic magnetic fields prevent the formation and survival of inner disk dust structures corotating with the star. Finally, we examined the characteristic variability timescales within each light curve and determined that the day-to-week timescales are predominant over the K2 time series. These reflect distinct processes and locations in the inner disk environment, from intense accretion triggered by instabilities in the innermost disk regions to variable accretion efficiency in the outer magnetosphere.

Keywords: young stellar objects; circumstellar disks; variable stars; young star clusters; multi-color photometry; time series analysis
Sensitivity of the Atmospheric Water Cycle within the Habitable Zone of a Tidally Locked, Earth-like Exoplanet

Synchronously orbiting, tidally locked exoplanets with a dayside facing their star and a permanently dark nightside orbiting dim stars are prime candidates for habitability. Simulations of these planets often show the potential to maintain an Earth-like climate with a complete hydrological cycle. Here we examine the sensitivity of the atmospheric water cycle to changes in stellar flux and describe the main underlying mechanisms. In a slowly rotating, tidally locked Earth-like atmospheric model, the response to a small (about 10%) increase in stellar irradiance from a habitable zone control simulation is examined. The water cycle is enhanced in response to the increased stellar irradiance. While the evaporation increase behaves similarly to the stellar radiation increase, the day-to-night energy transport by the mean circulation is critical to the planet's precipitation changes. Increased efficiency of the energy transport in a warmer climate shapes the substellar precipitation increase. On the nightside, precipitation changes are weak as a result of the large cancellation between the increased energy transport and the increased longwave emission. The day-to-night energy transport efficiency is sensitive to the variation of the atmosphere's vertical stratification. Due to weak temperature gradients in the upper troposphere and a moist adiabat maintained in the substellar region, variations in the substellar surface temperature and specific humidity govern the increase of the planet's stratification with warming. This suggests a scaling of the nightside's precipitation based on the substellar surface thermodynamic changes, a sensitivity that holds over a wider range of stellar irradiance changes.

Keywords: exoplanet atmospheres; astrobiology; extrasolar rocky planets
A Study of the Overall Evolution Behaviors of Pulses and Flares within Gamma-Ray Bursts

Many studies have shown that the X-ray flares in gamma-ray bursts (GRBs) have similar properties to the prompt emission pulses that occur in GRBs, suggesting that they may come from the same origin. We attempt to extend the evolution behavior that exists among GRBs to within individual GRBs. By selecting 12 GRBs with both multipulses and multiflares, we systematically study the overall evolution behaviors of the pulses and flares that occur within GRBs, including the width (w), peak time (t peak), rise time (t rise), decay time (t decay), and spectral lag. We find that correlated relationships exist within the GRBs, even if the overall evolution slopes of the pulses and flares in different GRBs are different. We also study the relations between the full pulse width (ω), the ratio of the rising width to the decay width (r/d), and the energy (E) of multipulses and multiflares within GRBs. It is found that there is a power-law anticorrelation between ω and E and a power-law correlation between r/d and E, with the mean values of the two power-law indexes being -0.42 and 0.07, respectively, which are very close to the values that are obtained for the prompt emission pulses. In addition, we find that the percentages of the positive lags for pulses and flares are 83% and 92%, respectively, with the lags of the flares being much larger than those of the pulses. Our results indicate that the overall evolution behaviors of the pulses and flares within individual GRBs are similar to the evolution behavior among GRBs, and that flares are low-energy extensions of pulses, providing further evidence that both come from the same origin.

Keywords: gamma-ray bursts
Characterizing Pulsars Detected in the Rapid ASKAP Continuum Survey

We present the detection of 661 known pulsars observed with the Australian SKA Pathfinder (ASKAP) telescope at 888 MHz as part of the Rapid ASKAP Continuum Survey (RACS). Detections were made through astrometric coincidence and we estimate the false alarm rate of our sample to be ~0.5%. Using archival data at 400 and 1400 MHz, we estimate the power-law spectral indices for the pulsars in our sample and find that the mean spectral index is -1.78 ± 0.6. However, we also find that a single power law is inadequate for modeling all the observed spectra. With the addition of flux densities between 150 MHz and 3 GHz from various imaging surveys, we find that up to 40% of our sample show deviations from a simple power-law model. Using Stokes V measurements from the RACS data, we measured the circular polarization fraction for 9% of our sample and find that the mean polarization fraction is ~10% (consistent between detections and upper limits). Using the dispersion-measure-derived distance, we estimate the pseudo-luminosity of the pulsars and do not find any strong evidence for a correlation with the pulsars' intrinsic properties.

Keywords: pulsars; radio pulsars; neutron stars; radio interferometry
A New Iron Emission Template for Active Galactic Nuclei. I. Optical Template for the Hβ Region

We present a new empirical template for iron emission in active galactic nuclei (AGNs) covering the 4000-5600 Å range. The new template is based on a spectrum of the narrow-line Seyfert 1 galaxy Mrk 493 obtained with the Hubble Space Telescope. In comparison with the canonical iron template object I Zw 1, Mrk 493 has narrower broad-line widths, lower reddening, and a less extreme Eddington ratio, making it a superior choice for template construction. We carried out a multicomponent spectral decomposition to produce a template incorporating all the permitted and forbidden lines of Fe II identified in the Mrk 493 spectrum over this wavelength range, as well as lines from Ti II, Ni II, and Cr II. We tested the template by fitting it to AGN spectra spanning a broad range of iron emission properties, and we present a detailed comparison with fits using other widely used monolithic and multicomponent iron emission templates. The new template generally provides the best fit (lowest χ 2) compared to other widely used monolithic empirical templates. In addition, the new template yields more accurate spectral measurements including a significantly better match of the derived Balmer line profiles (Hβ, Hγ, Hδ), in contrast with results obtained using the other templates. Our comparison tests show that the choice of iron template can introduce a systematic bias in measurements of the Hβ line width, which consequently impacts single-epoch black hole mass estimates by ~0.1 dex on average and possibly up to ~0.3-0.5 dex individually. * Based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-14744.

Keywords: supermassive black holes; seyfert galaxies; quasars; active galaxies; active galactic nuclei
A Mass Model for the Lensing Cluster SDSS J1004+4112: Constraints from the Third Time Delay

We have built a new model for the lens system SDSS J1004+4112 including the recently measured time delay of the fourth quasar image. This time delay has a strong influence on the inner mass distribution of the lensing cluster (ρ ∝ r -α ) allowing us to determine $\alpha ={1.18}_{-0.03(-0.18)}^{+0.02(+0.11)}$ at the 68% (95%) confidence level in agreement with hydrodynamical simulations of massive galaxy clusters. We find an offset between the brightest cluster galaxy and the dark matter halo of ${3.8}_{-0.7(-1.3)}^{+0.6(+1.4)}$ kpc at 68% (95%) confidence which is compatible with other galaxy cluster measurements. As an observational challenge, the estimated time delay between the leading image C and the faint (I = 24.7) fifth image E is roughly 8 yr.

Keywords: gravitational lensing; strong gravitational lensing; galaxy clusters; dark matter distribution; quasars
Searching for Extragalactic Star Formation in the M101 Group

We present deep, narrowband imaging of the nearby spiral galaxy M101 to search for star-forming dwarf galaxies and isolated H II regions in the group environment. Isolated star-forming regions, unassociated with spiral arms, probe star formation (SF) at the lowest masses and environmental densities. Such objects may be isolated star-forming events or ongoing evidence of tidal interactions. Using the Burrell Schmidt telescope, we target the brightest emission lines of star-forming regions, Hα, Hβ, and [O III], to detect potential isolated regions. Great care was taken to remove potential source contaminants, such as high-redshift objects and Galactic M stars, from our source list. For each detected source, we compare the emission line fluxes and equivalent widths, along with structural and photometric properties, to samples of Local Group dwarfs and star-forming galaxies in the SINGG/11HUGS samples. We discuss our findings in the context of SF in low-density environments and evolution of the M101 Group.

Keywords: star formation; narrow band photometry; galaxy evolution
A Statistical View of the Stable and Unstable Roche Lobe Overflow of a Tertiary Star onto the Inner Binary in Triple Systems

In compact stellar triple systems, an evolved tertiary star can overflow its Roche lobe around the inner binary. Subsequently, the tertiary star can transfer mass to the inner binary in a stable manner, or Roche lobe overflow (RLOF) can be unstable and lead to common-envelope (CE) evolution. In the latter case, the inner binary enters the extended envelope of the tertiary star and spirals in toward the donor's core, potentially leading to mergers or ejections. Although studied in detail for individual systems, a comprehensive statistical view on the various outcomes of triple RLOF is lacking. Here, we carry out 105 population synthesis simulations of tight triples, self-consistently taking into account stellar evolution, binary interactions, and gravitational dynamics. Also included are prescriptions for the long-term evolution of stable triple mass transfer, and triple CE evolution. Although simple and ignoring hydrodynamic effects, these prescriptions allow for a qualitative statistical study. We find that triple RLOF occurs in ~0.06% of all triple systems. Of these 0.06%, ~64% of cases lead to stable mass transfer, and ~36% to triple CE evolution. Triple CE is most often (~76%) followed by one or multiple mergers in short succession, most likely an inner binary merger of two main-sequence stars. Other outcomes of triple CE are a binary+single system (~23%, most of which do not involve exchange interactions), and a stable triple (~1%). We also estimate the rate of type Ia supernovae involving white dwarf mergers following triple RLOF, but find only a negligible contribution.

Keywords: stellar dynamics; stellar evolution; multiple star evolution; roche lobe overflow; common envelope evolution
Neutrinos from the Brightest Gamma-Ray Burst?

We discuss implications that can be obtained by searches for neutrinos from the brightest gamma-ray burst (GRB), GRB 221009A. We derive constraints on GRB model parameters such as the cosmic-ray loading factor and dissipation radius, taking into account both neutrino spectra and effective areas. The results are strong enough to constrain proton acceleration near the photosphere, and we find that the single burst limits are comparable to those from stacking analysis. Quasi-thermal neutrinos from subphotospheres and ultra-high-energy neutrinos from external shocks are not yet constrained. We show that GeV-TeV neutrinos originating from neutron collisions are detectable, and urge dedicated analysis on these neutrinos with DeepCore and IceCube as well as ORCA and KM3NeT.

Keywords: neutrino astronomy; high energy astrophysics; gamma-ray bursts; cosmic rays
Galaxy Light Profile Convolutional Neural Networks (GaLNets). I. Fast and Accurate Structural Parameters for Billion-galaxy Samples

Next-generation large sky surveys will observe up to billions of galaxies for which basic structural parameters are needed to study their evolution. This is a challenging task that, for ground-based observations, is complicated by seeing-limited point-spread functions (PSFs). To perform a fast and accurate analysis of galaxy surface brightness, we have developed a family of supervised convolutional neural networks (CNNs) to derive Sérsic profile parameters of galaxies. This work presents the first two Galaxy Light profile CNNs (GaLNets) of this family. The first one is trained using galaxy images only (GaLNet-1), and the second is trained with both galaxy images and the local PSF (GaLNet-2). We have compared the results from GaLNets with structural parameters (total magnitude, effective radius, Sérsic index, etc.) derived from a set of galaxies from the Kilo-Degree Survey by 2DPHOT as a representative of the "standard" PSF-convolved Sérsic fitting tools. The comparison shows that GaLNet-2 can reach an accuracy as high as that of 2DPHOT, while GaLNet-1 performs worse because it misses the information from the local PSF. Both GaLNets are three orders of magnitude faster than standard methods in terms of computational speed. This first application of CNNs to ground-based galaxy surface photometry shows that they are promising tools to perform parametric analyses of very large galaxy samples, like the ones expected from the Vera Rubin/LSST surveys. However, GaLNets can be easily modified for space observations from Euclid and the China Space Station Telescope.

Keywords: galaxy structure; galaxy formation; neural networks
A Spectroscopic Survey of Lyα Emitters and Lyα Luminosity Function at Redshifts 3.7 and 4.8

We present a spectroscopic survey of Lyα emitters (LAEs) at z ~ 3.7 and z ~ 4.8. The LAEs are selected using the narrowband technique based on the combination of deep narrowband and broadband imaging data in two deep fields, and then spectroscopically confirmed with the MMT multifiber spectrograph Hectospec. The sample consists of 71 LAEs at z ~ 3.7 and 69 LAEs at z ~ 4.8 over ~1.5 deg2, making it one of the largest spectroscopically confirmed samples of LAEs at the two redshifts. Their Lyα luminosities are measured using the secure redshifts and deep photometric data, and span a range of ~1042.5-1043.6 erg s-1, so these LAEs represent the most luminous galaxies at the redshifts in terms of Lyα luminosity. We estimate and correct sample incompletenesses and derive reliable Lyα luminosity function (LFs) at z ~ 3.7 and 4.8 based on the two spectroscopic samples. We find that our Lyα LFs are roughly consistent (within a factor of 2-3) with previous measurements at similar redshifts that were derived from either photometric samples or spectroscopic samples. By comparing with previous studies in different redshifts, we find that the Lyα LFs decrease mildly from z ~ 3.1 to z ~ 5.7, supporting the previous claim of the slow LF evolution between z ~ 2 and z ~ 6. At z > 5.7, the LF declines rapidly toward higher redshift, partly due to the effect of cosmic reionization.

Keywords: high-redshift galaxies; lyman-alpha galaxies; galaxy properties
Modeling Apsidal Motion in Eclipsing Binaries Using ELC

Apsidal motion is the precession of the line of apsides in the orbit of a binary star due to perturbations from General Relativity (GR), tides, or third-body interactions. The rate of precession due to tidal effects depends on the interior structures of the stars, and as a result, binaries in which this precession occurs are of great interest. Apsidal motion is observed through the analysis of eclipse times, which reveal small changes in the average interval between successive primary and secondary eclipses, taking all available observed times of eclipse and yielding an estimate of the apsidal rate. Given that this is a single observed quantity, various degeneracies are unavoidably present. Ideally, one would have a model that predicts eclipse times given the orbital and stellar parameters. These parameters for a given binary could then be computed using least squares, provided a suitably large number of eclipse times. Here we use the eclipsing light curve (ELC) program as such a model. The Newtonian equations of motion with additional force terms accounting for GR contributions and tidal distortions are integrated, yielding precise sky positions as a function of time. Times of mid-eclipse and instantaneous orbital elements are computed as a function of time. In this paper, we outline the method and compare numerically computed apsidal rates with standard formulae using a set of 15 binaries based on real systems. For our simulated systems, the derived apsidal rates agree with the standard formula.

Keywords: apsidal motion