adsabs/SciX_UAT_keywords huggingface dataset:
A High Incidence of Dusty Hα Emitters at z > 3 Among UltraVISTA Dropout Galaxies in COSMOS Revealed by JWST

We have characterized 26 Spitzer/IRAC-selected sources from the SMUVS program that are undetected in the UltraVISTA DR5 H- and/or K s-band images, covering 94 arcmin2 of the COSMOS field, which have deep multiwavelength JWST photometry. We analyzed the JWST/NIRCam imaging from the PRIMER survey and ancillary HST data to reveal the properties of these galaxies from spectral energy distribution (SED) fitting. We find that the majority of these galaxies are detected by NIRCam at λ < 2 μm, with only four remaining as near-infrared dropouts in the deeper JWST images. Our results indicate that the UltraVISTA dropouts candidates are primarily located at z > 3 and are characterized by high dust extinctions, with a typical color excess E(B ‑ V) = 0.5 ± 0.3 and stellar mass $\mathrm{log}({M}_{* }/{M}_{\odot })=9.5\pm 1.0$ . Remarkably, ∼75% of these sources show a flux enhancement between the observed photometry and modeled continuum SED that can be attributed to Hα emission in the corresponding NIRCam bands. The derived (Hα+ N [II] + S [II]) rest-frame equivalent widths and Hα star formation rates (SFRs) span values ∼100–2200 Å and ∼5–375 M ⊙ yr‑1, respectively. The locations of these sources on the SFR–M * plane indicate that 35% of them are starbursts, 40% are main-sequence galaxies, and the remaining 25% are located in the star formation valley. Our sample includes one active galactic nucleus and six submillimeter sources, as revealed from ancillary X-ray and submillimeter photometry. The high dust extinctions combined with the flux boosting from Hα emission explain why these sources are relatively bright Spitzer galaxies and yet unidentified in the ultradeep UltraVISTA near-infrared images.

Keywords: high-redshift galaxies; star formation; james webb space telescope
HD 165054: An Astrometric Calibration Field for High-contrast Imagers in Baade's Window

We present a study of the HD 165054 astrometric calibration field that has been periodically observed with the Gemini Planet Imager (GPI). HD 165054 is a bright star within Baade's Window, a region of the galactic plane with relatively low extinction from interstellar dust. HD 165054 was selected as a calibrator target due to the high number density of stars within this region (∼3 stars per square arcsecond with H < 22), necessary because of the small field of view of the GPI. Using nine epochs spanning over five years, we have fit a standard five-parameter astrometric model to the astrometry of seven background stars within close proximity to HD 165054 (ρ < 2″). We achieved a proper motion precision of ∼0.3 mas yr-1 and constrained the parallax of each star to be ≲1 mas. Our measured proper motions and parallax limits are consistent with the background stars being a part of the galactic bulge. Using these measurements, we find no evidence of any systematic trend of either the plate scale or the north angle offset of GPI between 2014 and 2019. We compared our model describing the motions of the seven background stars to observations of the same field in 2014 and 2018 obtained with Keck/NIRC2, an instrument with excellent astrometric calibration. We find that the predicted position of the background sources is consistent with that measured by NIRC2, within the uncertainties of the calibration of the two instruments. In the future, we will use this field as a standard astrometric calibrator for the upgrade of GPI and potentially for other high-contrast imagers.

Keywords: direct imaging; astrometry; astronomical instrumentation; astronomy data reduction
Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement

We present cosmological hydrodynamic simulations of a quasar-mass halo (Mhalo ≈ 1012.5 M⊙ at z = 2) that for the first time resolve gas transport down to the inner 0.1 pc surrounding the central massive black hole. We model a multiphase interstellar medium including stellar feedback by supernovae, stellar winds, and radiation, and a hyper-Lagrangian refinement technique increasing the resolution dynamically approaching the black hole. We do not include black hole feedback. We show that the subpc inflow rate (1) can reach ~6 M⊙ yr-1 roughly in steady state during the epoch of peak nuclear gas density (z ~ 2), sufficient to power a luminous quasar, (2) is highly time variable in the pre-quasar phase, spanning 0.001-10 M⊙ yr-1 on Myr timescales, and (3) is limited to short (~2 Myr) active phases (0.01-0.1 M⊙ yr-1) followed by longer periods of inactivity at lower nuclear gas density and late times (z ~ 1), owing to the formation of a hot central cavity. Inflowing gas is primarily cool, rotational support dominates over turbulence and thermal pressure, and star formation can consume as much gas as provided by inflows across 1 pc-10 kpc. Gravitational torques from multiscale stellar non-axisymmetries dominate angular momentum transport over gas self-torquing and pressure gradients, with accretion weakly dependent on black hole mass. Subpc inflow rates correlate with nuclear (but decouple from global) star formation and can exceed the Eddington rate by ×10. The black hole can move ~10 pc from the galaxy center on ~0.1 Myr. Accreting gas forms pc-scale, rotationally supported, obscuring structures often misaligned with the galaxy-scale disk. These simulations open a new avenue to investigate black hole-galaxy coevolution.

Keywords: agn host galaxies; quasars; galaxy nuclei; galaxy formation; galaxy evolution; cosmological evolution; black hole physics; supermassive black holes
Role of Intervening Mg II Absorbers on the Rotation Measure and Fractional Polarization of the Background Quasars

We probed the magnetic fields in high-redshift galaxies using excess extragalactic contribution to residual rotation measure (RRM) for quasar sightlines with intervening Mg II absorbers. Based on a large sample of 1132 quasars, we have computed RRM distributions broadening using median absolute deviation from the mean ( ${\sigma }_{\mathrm{rrm}}^{\mathrm{md}}$ ), and found it to be 17.1 ± 0.7 rad m-2 for 352 sightlines having Mg II intervening absorbers in comparison to its value of 15.1 ± 0.6 rad m-2 for 780 sightlines without such absorbers, resulting in an excess broadening ( ${\sigma }_{\mathrm{rrm}}^{\mathrm{ex}}$ ) of 8.0 ± 1.9 rad m-2 among these two subsamples. This value of ${\sigma }_{\mathrm{rrm}}^{\mathrm{ex}}$ , has allowed us to constrain the average strength of magnetic field (rest frame) in high-redshift galaxies responsible for these Mg II absorbers, to be ∼1.3 ± 0.3 μG at a median redshift of 0.92. This estimate of magnetic field is consistent with the reported estimate in earlier studies based on radio-infrared correlation and energy equipartition for galaxies in the local universe. A similar analysis on subsample split based on the radio spectral index, α (with Fν ∝ να), for flat (α ≥ -0.3; 315 sources) and steep (α ≤ -0.7; 476 sources) spectrum sources shows a significant ${\sigma }_{\mathrm{rrm}}^{\mathrm{ex}}$ (at 3.5σ level) for the former and absent in the latter. An anticorrelation found between the ${\sigma }_{\mathrm{rrm}}^{\mathrm{md}}$ and percentage polarization (p) with a similar Pearson correlation of -0.62 and -0.87 for subsamples with and without Mg II, respectively, suggests the main contribution for decrements in the p value to be intrinsic to the local environment of quasars.

Keywords: magnetic fields; quasars; galaxies; extragalactic astronomy
Properties of AGN Multiband Optical Variability in the HSC SSP Transient Survey

We study variability of active galactic nuclei (AGNs) by using the deep optical multiband photometry data obtained from the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) survey in the COSMOS field. The images analyzed here were taken with 8, 10, 13, and 15 epochs over three years in the g, r, I, and z bands, respectively. We identified 491 robust variable AGN candidates, down to I = 25 mag and with redshift up to 4.26. Ninety percent of the variability-selected AGNs are individually identified with the X-ray sources detected in the Chandra COSMOS Legacy survey. We investigate their properties in variability by using structure function analysis and find that the structure function for low-luminosity AGNs (Lbol ≲ 1045 erg s-1) shows a positive correlation with luminosity, which is the opposite trend for the luminous quasars. This trend is likely to be caused by a larger contribution of the host galaxy light for lower-luminosity AGNs. Using the model templates of galaxy spectra, we evaluate the amount of host galaxy contribution to the structure function analysis and find that dominance of the young stellar population is needed to explain the observed luminosity dependence. This suggests that low-luminosity AGNs at 0.8 ≲ z ≲ 1.8 are predominantly hosted in star-forming galaxies. The X-ray stacking analysis reveals the significant emission from the individually X-ray undetected AGNs in our variability-selected sample. The stacked samples show very large hardness ratios in their stacked X-ray spectrum, which suggests that these optically variable sources have large soft X-ray absorption by dust-free gas.

Keywords: active galactic nuclei; low-luminosity active galactic nuclei; agn host galaxies; active galaxies; supermassive black holes; optical observation
Signature of a Heliotail Organized by the Solar Magnetic Field and the Role of Nonideal Processes in Modeled IBEX ENA Maps: A Comparison of the BU and Moscow MHD Models

Energetic neutral atom (ENA) models typically require post-processing routines to convert the distributions of plasma and H atoms into ENA maps. Here we investigate how two kinetic-MHD models of the heliosphere (the BU and Moscow models) manifest in modeled ENA maps using the same prescription and how they compare with Interstellar Boundary Explorer (IBEX) observations. Both MHD models treat the solar wind as a single-ion plasma for protons, which include thermal solar wind ions, pick-up ions (PUIs), and electrons. Our ENA prescription partitions the plasma into three distinct ion populations (thermal solar wind, PUIs transmitted and ones energized at the termination shock) and models the populations with Maxwellian distributions. Both kinetic-MHD heliospheric models produce a heliotail with heliosheath plasma that is organized by the solar magnetic field into two distinct north and south columns that become lobes of high mass flux flowing down the heliotail; however, in the BU model, the ISM flows between the two lobes at distances in the heliotail larger than 300 au. While our prescription produces similar ENA maps for the two different plasma and H atom solutions at the IBEX-Hi energy range (0.5-6 keV), the modeled ENA maps require a scaling factor of ~2 to be in agreement with the data. This problem is present in other ENA models with the Maxwellian approximation of multiple ion species and indicates that either a higher neutral density or some acceleration of PUIs in the heliosheath is required.

Keywords: solar wind; heliopause; slow solar wind; fast solar wind; heliosphere; solar system; heliosheath; termination shock; interstellar medium; magnetohydrodynamics; magnetohydrodynamical simulations
CO and C I Emission in the Early Spectrum of the Nova V1391 Cassiopeiae

V1391 Cassiopeiae is one of a growing number of novae to show emission from carbon monoxide but only the second to display molecular absorption as well (after V2676 Ophiuchi). In this Research Note, we present a 0.69–5.2 μm spectrum that includes both the CO fundamental and first overtone as well as a prominent, very low ionization spectrum dominated by the lines of C I. Relative to the CO first overtone, the CO fundamental is a factor of ten weaker than expected if the emission were optically thin. Modeling of the spectral structure of the first overtone indicates a CO temperature of 4000 K and 13C/12C of 0.5. CO emission coexisted with strong C I and O I emission so carbon monoxide formation did not fully incorporate either of the constituent elements.

Keywords: classical novae
Near-Sun Switchback Boundaries: Dissipation with Solar Distance

The most surprising result from the first solar encounters by the Parker Solar Probe (PSP) is the large amount of brief magnetic field reversals often referred to as switchbacks. Switchbacks have previously been observed further downstream in the solar wind by spacecraft such as Helios 2 at 62 Rs from the Sun. However, these observations lack a distinct proton temperature increase detected inside switchbacks by PSP, implying that they are evolving over time to eventually reach a pressure balance at the switchback boundaries. We look at the evolution of switchback boundaries as a function of radial distance from the Sun, from closest approach at 35.7 Rs during PSP's first two encounters to beyond 80 Rs. Using magnetic field and proton data from PSP's FIELDS and SWEAP instruments, we perform a day-by-day superposed epoch analysis of the 25 switchbacks with the sharpest step-like boundaries. During both encounters we found the proton temperature spikes to gradually decline before vanishing completely around 55 Rs. Magnetic reversals and velocity spikes also steadily drop in magnitude, but eventually flatten out instead of disappearing. Most interestingly, proton temperature change ΔTp across switchback boundaries is found to reach 2 × 105 in magnitude below 40 Rs during PSP's outbound trajectory, but is an order of magnitude less on the inbound trajectory, suggesting a possible common change in switchback characteristics near closest approach during both encounters.

Keywords: the sun; solar wind; solar physics
Unveiling Sub-pc Supermassive Black Hole Binary Candidates in Active Galactic Nuclei

The elusive supermassive black hole binaries (SMBHBs) are thought to be the penultimate stage of galaxy mergers, preceding a final coalescence phase. SMBHBs are sources of continuous gravitational waves, possibly detectable by pulsar timing arrays; the identification of candidates could help in performing targeted gravitational wave searches. Due to SMBHBs' origin in the innermost parts of active galactic nuclei (AGN), X-rays are a promising tool for unveiling their presence, by means of either double Fe Kα emission lines or periodicity in their light curve. Here we report on a new method for selecting SMBHBs by means of the presence of a periodic signal in their Swift Burst Alert Telescope (BAT) 105 month light curves. Our technique is based on Fisher's exact g-test and takes into account the possible presence of colored noise. Among the 553 AGN selected for our investigation, only the Seyfert 1.5 galaxy Mrk 915 emerges as a candidate SMBHB; from subsequent analysis of its light curve we find a period P0 = 35 ± 2 months, and the null hypothesis is rejected at the 3.7σ confidence level. We also present a detailed analysis of the BAT light curve of the only previously X-ray-selected binary candidate source in the literature, the Seyfert 2 galaxy MCG+11-11-032. We find P0 = 26.3 ± 0.6 months, consistent with the one inferred from previously reported double Fe Kα emission lines.

Keywords: x-ray active galactic nuclei; seyfert galaxies
A Shining Death of Unequal Supermassive Black Hole Binaries

In the ΛCDM scenario, small galaxies merge to produce larger entities. Since supermassive black holes (SMBHs) are found in galaxies of all sizes, SMBH binaries (SMBHBs) are generally expected to form during the amalgamation of galaxies. It is unclear what fraction of these binaries could eventually merge, but a general consensus is that initially the orbital decay is mediated by the surrounding gas and stars. In this Letter, we show that in active galactic nuclei (AGNs) the radiation field also causes the orbits of the accreting SMBHs to shrink. The corresponding mechanism, known as the "Poynting-Robertson drag" (PR drag), takes effect on a well-defined timescale CTSal, where TSal is the Salpeter timescale of the AGN, presumably coinciding with the primary SMBH, and $C=4{\XI }^{-1}{\epsilon }^{-1}{q}^{1/3}{(1+q)}^{2/3}(1-\epsilon )$ is a constant determined by the radiative efficiency ɛ, the mass ratio q of the two black holes, and a parameter ξ characterizing the size of the circumsecondary accretion disk. We find that when q ≲ a few × 10-5, the PR drag is more efficient in shrinking the binary than many other mechanisms, such as dynamical friction and type-I migration. Our finding points to a possible new channel for the coalescence of unequal SMBHBs and the clearing of intermediate-massive black holes in AGNs.

Keywords: accretion; active galactic nuclei; gravitational waves; quasars; astrodynamics
Identification of Carbon Stars from LAMOST DR7

Carbon stars are excellent kinematic tracers of galaxies and play important roles in understanding the evolution of the Galaxy. Therefore, it is worthwhile to search for them in a large number of spectra. In this work, we build a new carbon star catalog based on the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) DR7 spectra. The catalog contains 4542 spectra of 3546 carbon stars, identified through line index and near-infrared color–color diagrams. Through visual inspection of the spectra, we further subclassify them into 925 C–H, 384 C–R, 608 C–N, and 1292 Ba stars. However, 437 stars could not be subclassified due to their low signal-to-noise. Moreover, by comparing with the LAMOST DR7 pipeline we find 567 more carbon stars and visually subclassify them. We find that on the J ‑ H versus H ‑ K s two-color diagram, C–N stars can be reliably distinguished from the other three subtypes. Additionally, by utilizing the Gaia distance, we study the distribution of carbon stars in the H-R diagram and identify 258 dwarf carbon stars by the criterion M G > 5.0 mag. Finally, we present the spatial distribution in Galactic coordinates of the 3546 carbon stars. The majority of C–N, C–R, and Ba stars are distributed at low Galactic latitudes, while most C–H and dwarf carbon stars are distributed at high Galactic latitudes.

Keywords: carbon stars; catalogs; sky surveys; astrostatistics
A Careful Reassessment of Globular Cluster Multiple Population Radial Distributions with Sloan Digital Sky Survey and Johnson-Cousins Broadband Photometry

Inconsistencies regarding the nature of globular cluster (GC) multiple population radial distributions is a matter for concern given their role in testing or validating cluster dynamical evolution modeling. In this study, we present a reanalysis of eight GC radial distributions using publicly available ground-based ugriz and UBVRI photometry; correcting for a systematic error identified in the literature. We detail the need for including and considering not only Kolmogorov-Smirnov (K-S) probabilities but critical K-S statistic values as well when drawing conclusions from radial distributions, as well as the impact of sample incompleteness. Revised cumulative radial distributions are presented, and the literature of each cluster is reviewed to provide a fuller picture of our results. We find that many multiple populations are not as segregated as once thought, and that there is a pressing need for better understanding of the spatial distributions of multiple populations in GCs.

Keywords: globular star clusters; broad band photometry; red giant branch; hertzsprung russell diagram; dynamical evolution
AT 2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-Ray Emission

High-cadence, multiwavelength observations have continuously revealed the diversity of tidal disruption events (TDEs), thus greatly advancing our knowledge and understanding of TDEs. In this work, we conducted an intensive optical-UV and X-ray follow-up campaign of TDE AT 2023lli and found a remarkable month-long bump in its UV/optical light curve nearly 2 months prior to maximum brightness. The bump represents the longest separation time from the main peak among known TDEs to date. The main UV/optical outburst declines as t ‑4.10, making it one of the fastest-decaying optically selected TDEs. Furthermore, we detected sporadic X-ray emission 30 days after the UV/optical peak, accompanied by a reduction in the period of inactivity. It is proposed that the UV/optical bump could be caused by the self-intersection of the stream debris, whereas the primary peak is generated by the reprocessed emission of the accretion process. In addition, our results suggest that episodic X-ray radiation during the initial phase of decline may be due to the patched obscurer surrounding the accretion disk, a phenomenon associated with the inhomogeneous reprocessing process. The double TDE scenario, in which two stars are disrupted in sequence, is also a possible explanation for producing the observed early bump and main peak. We anticipate that the multicolor light curves of TDEs, especially in the very early stages, and the underlying physics can be better understood in the near future with the assistance of dedicated surveys such as the deep high-cadence survey of the 2.5 m Wide Field Survey Telescope.

Keywords: tidal disruption; supermassive black holes; black hole physics; accretion
Study of γ-Ray Emission from a Compact Radio Galaxy with the Fermi Large Area Telescope

The radio galaxy PKS 1007+142 is classified as a compact steep-spectrum source (CSS) and belongs to the class of young active galactic nuclei (AGNs). In this paper, we investigate the γ-ray emission from this CSS by conducting a comprehensive analysis of the 15 yr Fermi Large Area Telescope (Fermi-LAT) observation data. The Fermi-LAT latest Source Catalog, 4FGL-DR4, includes an unassociated γ-ray source, 4FGL J1010.0+1416, located at 0.°24 away from the radio position of PKS 1007+142. Using the 15 yr Fermi-LAT observation data, we reestimate the best-fit position of the γ-ray source and find that PKS 1007+142 is in close proximity to the γ-ray source and falls within its 68% error circle. Therefore, we conclude that PKS 1007+142 is the most plausible counterpart to the unassociated LAT source with detection test statistics ∼ 43.4 (∼6.6σ). PKS 1007+142 exhibits a steep power-law spectrum in the 0.1–300 GeV band, with a photon spectral index (Γ γ ) of 2.86 ± 0.17. The average flux in the considered time interval is (2.14 ± 0.34) × 10‑12 erg cm‑2 s‑1. Comparing PKS 1007+142 with other γ-ray emitting AGNs in both the L γ –Γ γ and L γ –L 1.4 GHz planes, it shows a softer γ-ray spectrum and lower luminosity compared to other γ-ray emitting CSSs. Furthermore, the possible origins of γ-ray in PKS 1007+142 are also discussed.

Keywords: active galactic nuclei; relativistic jets; non-thermal radiation sources; gamma-ray sources
KMTNet Nearby Galaxy Survey: Overview and Survey Description

Recently, there has been increasing demand for deep imaging surveys to investigate the history of the mass assembly of galaxies in detail by examining the remnants of mergers and accretions, both of which have very low surface brightness (LSB). In addition, the nature of star formation in LSB regions, such as galaxy outer disks, is also an intriguing topic in terms of understanding the physical mechanisms of disk evolution. To address these issues, this study conducted a survey project, called the Korea Microlensing Telescope Network Nearby Galaxy Survey, to construct a deep imaging data set of nearby galaxies in the southern hemisphere. It provides deep and wide-field images with a field of view of ~12 deg2 for 13 nearby galaxies drawn from the Carnegie-Irvine Galaxy Survey catalog in optical broad bands (BRI) and an Hα narrow band. Through a dedicated data reduction, the surface brightness limit in 10″ × 10″ boxes was found to reach as deep as μ 1σ ~ 29-31 mag arcsec-2 in the optical broad bands and f 1σ ~ 1-2 × 10-18 erg s-1 cm-2 arcsec-2 in the Hα narrow band. To conclude the paper, several possible scientific applications for this data set are described.

Keywords: galaxy properties; photometry; astronomy data reduction; astronomy databases