adsabs/SciX_UAT_keywords huggingface dataset:
Stellar Initial Mass Function (IMF) Probed with Supernova Rates and Neutrino Background: Cosmic-average IMF Slope Is ≃2-3 Similar to the Salpeter IMF

The stellar initial mass function (IMF) is expressed by ϕ(m) ∝ m - α with the slope α, and known as a poorly constrained but very important function in studies of star and galaxy formation. There are no sensible observational constraints on the IMF slopes beyond the Milky Way and nearby galaxies. Here we combine two sets of observational results, (1) cosmic densities of core-collapse supernova (CCSN) explosion rates and (2) cosmic far-UV radiation (and infrared reradiation) densities, which are sensitive to massive (≃8-50 M ⊙) and moderately massive (≃2.5-7 M ⊙) stars, respectively, and constrain the IMF slope at m > 1 M ⊙ with a freedom of redshift evolution. Although no redshift evolution is identified beyond the uncertainties, we find that the cosmic-average IMF slope at z = 0 is α = 1.8-3.2 at the 95% confidence level that is comparable with the Salpeter IMF, α = 2.35, which marks the first constraint on the cosmic-average IMF. We show a forecast for the Nancy Grace Roman Space Telescope supernova survey that will provide significantly strong constraints on the IMF slope with δ α ≃ 0.5 over z = 0-2. Moreover, as for an independent IMF probe instead of (1), we suggest to use diffuse supernovae neutrino background (DSNB), relic neutrinos from CCSNe. We expect that the Hyper-Kamiokande neutrino observations over 20 yr will improve the constraints on the IMF slope and the redshift evolution significantly better than those obtained today, if the systematic uncertainties of DSNB production physics are reduced in the future numerical simulations.

Keywords: supernova neutrinos; core-collapse supernovae; optical observation; star formation; initial mass function
Enhanced Black Hole Mergers in Active Galactic Nucleus Disks due to Precession-induced Resonances

Recent studies have shown that active galactic nucleus (AGN) disks can host sources of gravitational waves. Compact binaries can form and merge in AGN disks through their interactions with the gas and other compact objects in the disk. It is also possible for the binaries to shorten the merging timescale due to eccentricity excitation caused by perturbations from the supermassive black hole (SMBH). In this paper, we focus on effects due to precession-induced (eviction-like) resonances, where the nodal and apsidal precession rates of the binary are commensurable with the mean motion of the binary around the SMBH. We focus on intermediate-mass black hole (IMBH)-stellar-mass black hole binaries and consider binary orbit inclined from the circum-IMBH disk, which leads to the orbital J 2 precession. We show that if a binary is captured in these resonances and is migrating toward the companion, it can undergo large eccentricity and inclination variations. We derive analytical expressions for the location of fixed points, libration timescale, and width for these resonances and identify two resonances in the near-coplanar regime (the evection and eviction resonances) as well as two resonances in the near-polar regime that can lead to mergers. We also derive analytical expressions for the maximum eccentricity that a migrating binary can achieve for given initial conditions. Specifically, the maximum eccentricity can reach 0.9 when captured in these resonances before orbital decay due to gravitational-wave emission dominates, and the capture is only possible for slow migration (~10 Myr) two to three orders of magnitude longer than the resonance libration timescale. We also show that capture into multiple resonances is possible and can further excite eccentricities.

Keywords: black holes; active galactic nuclei; three-body problem; perturbation methods
The Last Journey. II. SMACC—Subhalo Mass-loss Analysis Using Core Catalogs

This paper introduces Subhalo Mass-loss Analysis using Core Catalogs (SMACC). SMACC adds a mass model to substructure merger trees based on halo "core tracking." Our approach avoids the need for running expensive subhalo finding algorithms and instead uses subhalo mass-loss modeling to assign masses to halo cores. We present details of the SMACC methodology and demonstrate its excellent performance in describing halo substructure and its evolution. Validation of the approach is carried out using cosmological simulations at significantly different resolutions. We apply SMACC to the 1.24-trillion-particle Last Journey simulation and construct core catalogs with the additional mass information. These catalogs can be readily used as input to semianalytic models or subhalo abundance matching approaches to determine approximate galaxy distributions, as well as for in-depth studies of small-scale structure evolution.

Keywords: n-body simulations; cosmology; large-scale structure of the universe
The Far Ultraviolet Light Curve of 78 Vir (A2p SrCrEu)

All IUE spectra obtained shortwards of 2000 Å with the SWP camera are used to construct a far-ultraviolet (FUV) light curve at 1500 Å for 78 Vir over its rotational period. Setting an arbitrary phase 0.00 for the first spectrum recorded on 1987 May 10, the minimum and maximum occur respectively near phases 0.20–0.25 and 0.60–0.70. The Fine Error Sensor counts, which measure the brightness near the V band, vary in phase with the FUV flux, which is the opposite situation to that observed in another cool Ap star, 21 Com.

Keywords: chemically peculiar stars; ap stars
Early JWST Imaging Reveals Strong Optical and NIR Color Gradients in Galaxies at z 2 Driven Mostly by Dust

Recent studies have shown that galaxies at cosmic noon are redder in the center and bluer in the outskirts, mirroring results in the local universe. These color gradients could be caused by gradients in either the stellar age or dust opacity; however, distinguishing between these two causes is impossible with rest-frame optical photometry alone. Here we investigate the underlying causes of the gradients from spatially resolved rest-frame U - V versus V - J color-color diagrams measured from early observations with the James Webb Space Telescope. We use 1-4 μm NIRCam photometry from the CEERS survey of a sample of 54 galaxies with $\mathrm{log}{M}_{* }/{M}_{\odot }\gt 10$ at redshifts 1.7 < z < 2.3 selected from the 3D-HST catalog. We model the light profiles in the F115W, F200W, and F356W NIRCam bands using imcascade, a Bayesian implementation of the multi-Gaussian expansion technique that flexibly represents galaxy profiles using a series of Gaussians. We construct resolved rest-frame U - V and V - J color profiles. The majority of star-forming galaxies have negative gradients (i.e., redder in the center, bluer in the outskirts) in both U - V and V - J colors consistent with radially decreasing dust attenuation. A smaller population (roughly 15%) of star-forming galaxies have positive U - V but negative V - J gradients implying centrally concentrated star formation. For quiescent galaxies, we find a diversity of UVJ color profiles, with roughly one-third showing star formation in their center. This study showcases the potential of JWST to study the resolved stellar populations of galaxies at cosmic noon.

Keywords: galaxy structure; high-redshift galaxies; galaxy colors
Three-dimensional Reconstruction of Weak-lensing Mass Maps with a Sparsity Prior. I. Cluster Detection

We propose a novel method to reconstruct high-resolution three-dimensional mass maps using data from photometric weak-lensing surveys. We apply an adaptive LASSO algorithm to perform a sparsity-based reconstruction on the assumption that the underlying cosmic density field is represented by a sum of Navarro-Frenk-White halos. We generate realistic mock galaxy shear catalogs by considering the shear distortions from isolated halos for the configurations matched to the Subaru Hyper Suprime-Cam Survey with its photometric redshift estimates. We show that the adaptive method significantly reduces line-of-sight smearing that is caused by the correlation between the lensing kernels at different redshifts. Lensing clusters with lower mass limits of 1014.0 h-1 M⊙, 1014.7 h-1 M⊙, 1015.0 h-1 M⊙ can be detected with 1.5σ confidence at the low (z < 0.3), median (0.3 ≤ z < 0.6), and high (0.6 ≤ z < 0.85) redshifts, respectively, with an average false detection rate of 0.022 deg-2. The estimated redshifts of the detected clusters are systematically lower than the true values by Δz ~ 0.03 for halos at z ≤ 0.4, but the relative redshift bias is below 0.5% for clusters at 0.4 < z ≤ 0.85. The standard deviation of the redshift estimation is 0.092. Our method enables direct three-dimensional cluster detection with accurate redshift estimates.

Keywords: cosmology; weak gravitational lensing; galaxy clusters; galaxy dark matter halos
A Cosmological Fireball with 16% Gamma-Ray Radiative Efficiency

Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. How efficiently the jet converts its energy to radiation is a long-standing problem, which is poorly constrained. The standard model invokes a relativistic fireball with a bright photosphere emission component. A definitive diagnosis of GRB radiation components and the measurement of GRB radiative efficiency require prompt emission and afterglow data, with high resolution and wide band coverage in time and energy. Here, we present a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its fluence is one of the highest for all the GRBs that have been detected so far, which allows us to perform a high-resolution study of the prompt emission spectral properties and their temporal evolutions, down to a timescale of about 0.1 s. We observe that each of the initial pulses has a thermal component contributing ~20% of the total energy and that the corresponding temperature and inferred Lorentz factor of the photosphere evolve following broken power-law shapes. From the observation of the nonthermal spectra and the light curve, the onset of the afterglow corresponding to the deceleration of the fireball is considered to start at ~6 s. By incorporating the thermal and nonthermal observations, as well as the photosphere and synchrotron radiative mechanisms, we can directly derive the fireball energy budget with little dependence on hypothetical parameters, measuring a ~16% radiative efficiency for this GRB. With the fireball energy budget derived, the afterglow microphysics parameters can also be constrained directly from the data.

Keywords: gamma-ray bursts
The Stark Effect, Zeeman Effect, and Transition Dipole Moments for the B2Σ+-X2Σ+ Band of Aluminum Monoxide, AlO

The experimentally measured radiative lifetimes and branching ratios were combined to determine the transition dipole moments for the B2Σ+(V = 0-3) → X2Σ+(V = 0-6) bands of aluminum monoxide, AlO, and compared with theoretical predictions. The B2Σ+-X2Σ+ (0, 1) band of a molecular beam sample of AlO was recorded at high spectral resolution both field-free and in the presence of static electric and magnetic fields. The 27Al(I = 5/2) hyperfine interaction in the B2Σ+(V = 0) state was analyzed. The observed Stark shifts were analyzed to produce permanent electric dipole moments of 1.94(8) D and 4.45(3) D for the B2Σ+(V = 0) and X2Σ+(V = 1) states, respectively. It is demonstrated that the observed Zeeman spectra can be simulated using an effective Hamiltonian with the associated expected g-factors for both the X2Σ+(V = 1) and B2Σ+(V = 0) states.

Keywords: molecular spectroscopy; line intensities; transition probabilities; magnetic fields; circumstellar dust; circumstellar clouds; circumstellar gas; radio astronomy
Sun-as-a-star Observations of Obscuration Dimmings Caused by Filament Eruptions

Filament eruptions often lead to coronal mass ejections (CMEs) on the Sun and are one of the most energetic eruptive phenomena in the atmospheres of other late-type stars. However, the detection of filament eruptions and CMEs on stars beyond the solar system is challenging. Here, we present six filament eruption cases on the Sun and show that filament material obscuring part of the solar disk can cause detectable dimming signatures in Sun-as-a-star flux curves of He II 304 Å. Those filament eruptions have similar morphological features, originating from small filaments inside active regions and subsequently strongly expanding to obscure large areas of the solar disk or the bright flare regions. We have tracked the detailed evolution of six obscuration dimmings and estimated the dimming properties, such as dimming depths, dimming areas, and duration. The largest dimming depth among the six events under study is 6.2% accompanied by the largest dimming area of 5.6% of the solar disk area. Other events have maximum dimming depths in a range of around 1%–3%, with maximum areas varying between about 3%–4% of the solar disk area. The duration of the dimming spans from around 0.4–7.0 hr for the six events under study. A positive correlation was found between the dimming depth and area, which may help to set constraints on the filament sizes in stellar observations.

Keywords: solar coronal mass ejections; stellar coronal dimming; solar extreme ultraviolet emission; spectroscopy
Properties of Trans-fast Magnetosonic Jets in Black Hole Magnetospheres

Traveling across several orders of magnitude in distance, relativistic jets from strong gravity regions to asymptotic flat spacetime regions are believed to consist of several general relativistic magnetohydrodynamic (GRMHD) processes. We present a semianalytical approach for modeling the global structures of a trans-fast magnetosonic relativistic jet, which should be ejected from a plasma source near a black hole in a funnel region enclosed by dense accreting flow and a disk corona around the black hole. Our model consistently includes the inflow and outflow part of the GRMHD solution along the magnetic field lines penetrating the black hole horizon. After the rotational energy of the black hole is extracted electromagnetically by the negative energy GRMHD inflow, the huge electromagnetic energy flux propagates from the inflow to the outflow region across the plasma source, and in the outflow region, the electromagnetic energy converts to the fluid kinetic energy. Eventually, the accelerated outflow must exceed the fast magnetosonic wave speed. We apply the semianalytical trans-fast magnetosonic flow model to the black hole magnetosphere for both parabolic and split-monopole magnetic field configurations and discuss the general flow properties, that is, jet acceleration, jet magnetization, and the locations of some characteristic surfaces of the black hole magnetosphere. We have confirmed that, at large distances, the GRMHD jet solutions are in good agreement with the previously known trans-fast special relativistic magnetohydrodynamic jet properties, as expected. The flexibility of the model provides a prompt and heuristic way to approximate the global GRMHD trans-fast magnetosonic jet properties.

Keywords: rotating black holes; relativistic jets; magnetic fields; magnetohydrodynamics; galaxy jets; jets; black hole physics; astrophysical black holes; kerr black holes; accretion
A Study of the Radio Spectrum of Mrk 421

We present the results of a spectral analysis using simultaneous multifrequency (22, 43, 86, and 129 GHz) very long baseline interferometry (VLBI) observations of the Korean VLBI Network on BL Lac object, Markarian 421. The data we used were obtained from 2013 January to 2018 June. The light curves showed several flux enhancements with global decreases. To separate the variable and quiescent components in the multifrequency light curves for milliarcsecond-scale emission regions, we assumed that the quiescent radiation comes from the emission regions radiating constant optically thin synchrotron emissions (i.e., a minimum flux density with an optically thin spectral index). The quiescent spectrum determined from the multifrequency light curves was subtracted from the total CLEAN flux density, yielding a variable component in the flux that produces the time-dependent spectrum. We found that the observed spectra were flat at 22–43 GHz, and relatively steep at 43–86 GHz, whereas the quiescent-corrected spectra are sometimes quite different from the observed spectra (e.g., sometimes inverted at 22–43 GHz). The quiescent-corrected spectral indices were much more variable than the observed spectral indices. This spectral investigation implies that the quiescent-spectrum correction can significantly affect the multifrequency spectral index of variable compact radio sources such as blazars. Therefore, the synchrotron self-absorption B-field strength (B SSA) can be significantly affected because B SSA is proportional to the fifth power of turnover frequency.

Keywords: markarian galaxies; blazars; bl lacertae objects; active galaxies; relativistic jets
TESS Asteroseismic Analysis of HD 76920: The Giant Star Hosting an Extremely Eccentric Exoplanet

The Transiting Exoplanet Survey Satellite (TESS) mission searches for new exoplanets. The observing strategy of TESS results in high-precision photometry of millions of stars across the sky, allowing for detailed asteroseismic studies of individual systems. In this work, we present a detailed asteroseismic analysis of the giant star HD 76920 hosting a highly eccentric giant planet (e = 0.878) with an orbital period of 415 days, using five sectors of TESS light curve that cover around 140 days of data. Solar-like oscillations in HD 76920 are detected around 52 μHz by TESS for the first time. By utilizing asteroseismic modeling that takes classical observational parameters and stellar oscillation frequencies as constraints, we determine improved measurements of the stellar mass (1.22 ± 0.11 M ⊙), radius (8.68 ± 0.34 R ☉), and age (5.2 ± 1.4 Gyr). With the updated parameters of the host star, we update the semimajor axis and mass of the planet as a = 1.165 ± 0.035 au and ${M}_{{\rm{p}}}\sin i=3.57\pm 0.22\,{M}_{\mathrm{Jup}}$ . With an orbital pericenter of 0.142 ± 0.005 au, we confirm that the planet is currently far away enough from the star to experience negligible tidal decay until being engulfed in the stellar envelope. We also confirm that this event will occur within about 100 Myr, depending on the stellar model used.

Keywords: asteroseismology; exoplanets; red giant stars
Asymmetry in the Length Scales of the Solar Supergranulation Network

Supergranulation is the horizontal velocity pattern on the solar surface with a typical size of 30,000 km and a lifetime of 24 hr. The network structure seen in chromospheric lines, such as Ca II K 3934 Å, is the manifestation of supergranulation. The network seen in the extreme-ultraviolet lines like He II 304 Å is the extension of the chromospheric network into the upper solar atmosphere. We have obtained the length scales of the supergranulation network from the autocorrelation function of calcium II K spectroheliograms from the Kodaikanal archival data. The behavior of the length scales in the horizontal (parallel to the direction of rotation) and vertical (perpendicular to the direction of rotation) have been obtained in different latitudes for a period of about 100 yr. The time-averaged length scales show a nearly symmetric variation in the northern and southern hemispheres. The length scales also show a profound asymmetry in the horizontal and vertical directions, which is dependent on solar latitude. A comparison reveals that both length scales are almost equal near the equatorial latitudes, but the vertical length scales relatively become smaller toward higher latitudes. The asymmetry is independently verified from He II 304 Å images from the Solar Dynamic Observatory/Atmospheric Imaging Assembly. As the length scales are related to the width of the network, the results point to the asymmetry in the supergranular cell boundary. Supergranulation is one of the basic length scales of solar convection, hence these results can have implications for the convection in Sun-like stars.

Keywords: solar atmosphere; solar cycle; solar chromosphere
The HETDEX Survey: The Lyα Escape Fraction from 3D-HST Emission-Line Galaxies at z ∼ 2

In this work, we measure the Lyα escape fraction of 935 [O III]-emitting galaxies between 1.9 < z < 2.35 by comparing stacked spectra from the Hubble Space Telescope/WFC3's near-IR grism to corresponding stacks from the Hobby-Eberly Telescope Dark Energy Experiment's Internal Data Release 2. By measuring the stacks' Hβ to Lyα ratios, we determine the Lyα escape fraction as a function of stellar mass, star-formation rate, internal reddening, size, and [O III]/Hβ ratio. We show that the escape fraction of Lyα correlates with a number of parameters, such as galaxy size, star-formation rate, and nebular excitation. However, we also demonstrate that most of these relations are indirect, and that the primary variables controlling the escape of Lyα are likely to be stellar mass and internal extinction. Overall, the escape of Lyα declines from ≳16% in galaxies with $\mathrm{log}M/{M}_{\odot }\lesssim 9$ to ≲1% for systems with $\mathrm{log}M/{M}_{\odot }\gtrsim 10$ , with the sample's mean escape fraction being ${6.0}_{-0.5 \% }^{+0.6 \% }$ .

Keywords: observational cosmology; galaxy evolution; galaxy formation; high-redshift galaxies
Galaxy and Mass Assembly (GAMA): Low-redshift Quasars and Inactive Galaxies Have Similar Neighbors

We explore the properties of galaxies in the proximity (within a ~2 Mpc radius sphere) of Type I quasars at 0.1 <z <0.35, to check whether and how an active galaxy influences the properties of its neighbors. We further compare these with the properties of neighbors around inactive galaxies of the same mass and redshift within the same volume of space, using the Galaxy and Mass Assembly spectroscopic survey. Our observations reveal no significant difference in properties such as the number of neighbors, morphologies, stellar mass, star formation rates, and star formation history between the neighbors of quasars and those of the comparison sample. This implies that quasar activity in a host galaxy does not significantly affect its neighbors (e.g., via interactions with the jets). Our results suggest that quasar host galaxies do not strongly differ from the average galaxy within the specified mass and redshift range. Additionally, the implication of the relatively minor importance of the environmental effect on and from quasars is that nuclear activity is more likely triggered by internal and secular processes.

Keywords: galaxy evolution; quasars; active galaxies; active galactic nuclei; star formation; galaxy environments; galaxies; companion galaxies; supermassive black holes; galaxy mergers
Cosmic Reionization on Computers: Statistics, Physical Properties, and Environments of Lyman Limit Systems at z ∼ 6

Lyman limit systems (LLSs) are dense hydrogen clouds with high enough H I column densities to absorb Lyman continuum photons emitted from distant quasars. Their high column densities imply an origin in dense environments; however, the statistics and distribution of LLSs at high redshifts still remain uncertain. In this paper, we use self-consistent radiative transfer cosmological simulations from the Cosmic Reionization on Computers (CROC) project to study the physical properties of LLSs at the tail end of cosmic reionization at z ∼ 6. We generate 3000 synthetic quasar sight lines to obtain a large number of LLS samples in the simulations. In addition, with the high physical fidelity and resolution of CROC, we are able to quantify the association between these LLS samples and nearby galaxies. Our results show that the fraction of LLSs spatially associated with nearby galaxies increases with H I column density. Moreover, we find that LLSs that are not near any galaxy typically reside in filamentary structures connecting neighboring galaxies in the intergalactic medium (IGM). This quantification of the distribution and association of LLSs to large-scale structure informs our understanding of the IGM–galaxy connection during the "Epoch of Reionization," and provides a theoretical basis for interpreting future observations.

Keywords: reionization; intergalactic medium; lyman limit systems