Sazuna/UAT_keywords huggingface dataset:
Multiwavelength Constraints on the Local Black Hole Occupation Fraction. The fraction of dwarf galaxies hosting central, intermediate-mass black holes (IMBHs) at low redshifts is an important observational probe of black hole seeding at high redshift. Detections of nuclear accretion signatures in dwarf galaxies provides strong evidence for the presence of these IMBHs. We develop a Bayesian model to infer the black hole occupation fraction assuming a broken power-law Eddington ratio distribution function. Our approach accounts for nondetections, incompleteness, and contamination from star-forming-related emission. We apply this model to galaxies with X-ray data from the Chandra Source Catalog at distances &lt;50 Mpc, radio data from the Very Large Array Sky Survey at &lt;50 Mpc, and optical variability data from the Palomar Transient Factory at z &lt; 0.055. We find a black hole occupation fraction of at least 90% at stellar masses of M ⋆ = 108 M ⊙ and at least 39% at M ⋆ = 107 M ⊙ (95% confidence intervals). We show the resulting black hole mass function. These constraints on the IMBH population have implications for the Laser Interferometer Space Antenna mission and for cosmological models of black hole seeding and growth. We also constrain the extremely low-luminosity end (L bol ≲ 1040 erg s‑1) of the active galactic nucleus (AGN) luminosity functions at z = 0. Our AGN luminosity functions are broadly consistent with an extrapolation of the shallow slope of the AGN luminosity functions from previous work.

Keywords: Intermediate-mass black holes, Low-luminosity active galactic nuclei, Active galactic nuclei
Modeling the Center-to-limb Systematic in Normal-mode Coupling Measurements. Solar meridional circulation (MC), which manifests as poleward flow near the surface, is a relatively weak flow. While MC has been measured through various local helioseismic techniques, there is a lack of consensus about the nature of the depth profile and location of return flow, owing to its small amplitude and poor signal-to-noise ratio in observations. The measurements are strongly hampered by systematic effects whose amplitudes are comparable to the signal induced by the flow, and modeling them is therefore crucial. The removal of the center-to-limb (C2L) systematic, which is the largest known feature hampering the inference of meridional flow, has been heuristically performed in helioseismic analyses, but its effect on global modes is not fully understood or modeled. Here, we propose both a way to model the C2L systematic and a method for estimation of meridional flow using global helioseismic cross-spectral analysis. We demonstrate that the systematic cannot be ignored while modeling the mode-coupling cross-spectral measurement, and thus is critical for the inference of MC. We also show that inclusion of a model for the C2L systematic improves shallow MC estimates from cross-spectral analysis.

Keywords: Helioseismology, Center to limb observations, Solar cycle, Solar meridional circulation
LMC Calls, Milky Way Halo Answers: Disentangling the Effects of the MW–LMC Interaction on Stellar Stream Populations. The infall of the LMC into the Milky Way (MW) has dynamical implications throughout the MW's dark matter halo. We study the impact of this merger on the statistical properties of populations of simulated stellar streams. Specifically, we investigate the radial and on-sky angular dependence of stream perturbations caused by the direct effect of stream–LMC interactions and/or the response of the MW dark matter halo. We use a time-evolving MW–LMC simulation described by basis function expansions to simulate streams. We quantify the degree of perturbation using a set of stream property statistics including the misalignment of proper motions with the stream track. In the outer halo, direct stream–LMC interactions produce a statistically significant effect, boosting the fraction of misaligned proper motions by ∼25% relative to the model with no LMC. Moreover, there is on-sky angular dependence of stream perturbations: the highest fractions of perturbed streams coincide with the same on-sky quadrant as the present-day LMC location. In the inner halo, the MW halo dipole response primarily drives stream perturbations, but it remains uncertain whether this is a detectable signature distinct from the LMC's influence. For the fiducial MW–LMC model, we find agreement between the predicted fraction of streams with significantly misaligned proper motions,  , and Dark Energy Survey data. Finally, we predict this fraction for the Rubin Observatory Legacy Survey of Space and Time (LSST) footprint. Using LSST data will improve our constraints on dark matter models and LMC properties, as it is sensitive to both.

Keywords: Milky Way dynamics, Stellar streams, Large Magellanic Cloud
Pulse-profile Modeling and Spin─Orbit Alignment in a Suzaku Sample of Accreting X-Ray Binary Pulsars. We report pulse-profile modeling of a sample of 23 X-ray binary pulsars observed with the Suzaku X-ray satellite. These pulsars have spin periods ranging from 0.7 to 9400 s, and their X-ray emission is powered by the accretion from their stellar companions. We fitted each individual pulse profile with the Polestar geometric model, which accounts for X-ray emission from two hot spots modeled as a simple combination of fan+pencil beam components, including an approximation for gravitational light bending. In 14 of 21 cases, our measurements of the inclinations of the pulsar spin axes broadly agree with the corresponding inclinations of the orbital planes of the binary systems determined by various other means, a striking outcome with a mere 6 × 10−7 probability of occurring by chance. The implications of our study are as follows: (a) apparently, accretion torques have had time to erase spin─orbit misalignment caused by supernova kicks in two-thirds of the systems; (b) many X-ray binary pulsars have dominant dipolar surface magnetic fields, in contrast to the recently reported exotic configurations in millisecond pulsars; and (c) if the binary inclinations can be determined by pulse-profile modeling, even for a subset of the ∼200 known X-ray binary pulsars, most of which orbital inclinations are as yet poorly constrained, it raises the prospect of tightening dramatically ongoing neutron-star mass determinations. This is because masses in binary systems overwhelmingly come from an orbital-mechanics formulation (Kepler's third law), in which the dominant source of uncertainty is the inclination of the orbital plane.

Keywords: Pulsars
Rising Near-ultraviolet Spectra in Stellar Megaflares. Flares from M dwarf stars can attain energies up to 104 times larger than solar flares but are generally thought to result from similar processes of magnetic energy release and particle acceleration. Larger heating rates in the low atmosphere are needed to reproduce the shape and strength of the observed continua in stellar flares, which are often simplified to a blackbody model from the optical to the far-ultraviolet (FUV). The near-ultraviolet (NUV) has been woefully undersampled in spectral observations despite this being where the blackbody radiation should peak. We present Hubble Space Telescope NUV spectra in the impulsive phase of a flare with E TESS ≈ 7.5 × 1033 erg and a flare with E TESS ≈ 1035 erg and the largest NUV flare luminosity observed to date from an M star. The composite NUV spectra are not well represented by a single blackbody that is commonly assumed in the literature. Rather, continuum flux rises toward shorter wavelengths into the FUV, and we calculate that an optical T = 104 K blackbody underestimates the short-wavelength NUV flux by a factor of ≈6. We show that rising NUV continuum spectra can be reproduced by collisionally heating the lower atmosphere with beams of E ≳ 10 MeV protons or E ≳ 500 keV electrons and flux densities of 1013 erg cm‑2 s‑1. These are much larger than the canonical values describing accelerated particles in solar flares.

Keywords: Red dwarf flare stars, Near ultraviolet astronomy
Radiatively Active Clouds and Magnetic Effects Explored in a Grid of Hot Jupiter GCMs. Cloud formation and magnetic effects are both expected to significantly impact the structures and observable properties of hot Jupiter atmospheres. For some hot Jupiters, thermal ionization and condensation can coexist in a single atmosphere, and both processes are important. We present a grid of general circulation models across a wide range of irradiation temperatures with and without incorporating the effects of magnetism and cloud formation to investigate how these processes work in tandem. We find that clouds are present in the atmosphere at all modeled irradiation temperatures, while magnetic effects are negligible for planets with irradiation temperatures cooler than 2000 K. At and above this threshold, clouds and magnetic fields shape atmospheres together, with mutual feedback. Models that include magnetism, through their influence on the temperature structure, produce more longitudinally symmetric dayside cloud coverage and more equatorially concentrated clouds on the nightside and morning terminator. To indicate how these processes would affect observables, we generate bolometric thermal and reflected phase curves from these models. The combination of clouds and magnetic effects increases thermal phase-curve amplitudes and decreases peak offsets more than either process does individually.

Keywords: Exoplanet atmospheric dynamics, Exoplanet astronomy, Hot Jupiters
Mapping the Dense Molecular Gas toward 13 Supernova Remnants. Supernova remnants (SNRs) can exert strong influence on molecular clouds (MCs) through interaction by shock wave and cosmic rays. In this paper, we present our mapping observation of HCO+ and   1–0 lines toward 13 SNRs interacting with MCs, together with archival data of CO isotopes. Strong HCO+ emission is found in the fields of view of SNRs W30, G9.7‑0.0, Kes 69, 3C 391, 3C 396, W51C, HC 40, and CTB109 in the local-standard-of-rest velocity intervals in which they are suggested to show evidence of SNR–MC interaction. We find an incomplete 12CO shell surrounding G9.7‑0.0 with an expanding motion. This shell may be driven by the stellar wind of the SNR progenitor. We also find an arc of 12CO gas spatially coincident with the northwestern radio shell of Kes 69. As for the HCO+ line emission, SNRs 3C 391 and W51C exhibit significant line profile broadening indicative of shock perturbation, and CTB109 exhibits a possible blueshifted line wing brought by shock interaction. We do not find significant variation of the   line ratio between broad-line and narrow-line regions, among different SNRs, and between MCs associated with SNRs and typical Galactic MCs. Therefore, we caution on using the   line ratio as a diagnostic of SNR feedback and cosmic-ray (CR) ionization. We also estimate the N(HCO+)/N(CO) abundance ratio in 11 regions toward the observed SNRs, but they show little difference from the typical values in quiescent MCs, possibly because N(HCO+)/N(CO) is not an effective tracer of CR ionization.

Keywords: Supernova remnants, Molecular clouds
Young Stellar Object Jets Magnetocentrifugally Driven by Reconnecting Atmospheric Avalanche Accretion Streams above Inner Circumstellar Disks. Fast, collimated jets are ubiquitous features of young stellar objects. They are generally thought to be powered by disk accretion, but the details are debated. Through 2D (axisymmetric) MHD simulations, we find that a fast (&gt;100 km s−1) collimated bipolar jet is continuously driven along the north and south poles of a circumstellar disk that is initially magnetized by a large-scale open poloidal field and contains a thermally ionized inner magnetically active zone surrounded by a dead zone. The fast jet is primarily driven magnetocentrifugally by the release of the gravitational binding energy of the so-called "avalanche accretion streams" near the boundary of an evacuated poloidal field dominated polar region and a thick disk atmosphere raised by a toroidal magnetic field. Specifically, the fast outflow is driven along the upper (open) branch of the highly pinched poloidal field lines threading the (strongly magnetically braked) accretion streams, where the density is relatively low so that the lightly loaded material can be accelerated magnetocentrifugally along the open field line to a high speed. The highly pinched poloidal magnetic fields threading the avalanche accretion streams tend to reconnect, enabling mass to accrete to the center without dragging along the poloidal magnetic flux with it. The reconnection provides a potential heating source for producing chondrules and calcium- and aluminum-rich inclusions.

Keywords: Accretion, Young stellar objects, Jets, Circumstellar disks
The Mega-MUSCLES Treasury Survey: X-Ray to Infrared Spectral Energy Distributions of a Representative Sample of M Dwarfs. We present 5–1 × 107 Å spectral energy distributions (SEDs) for 12 M dwarf stars covering spectral types M0–M8. Our SEDs are provided for community use as a sequel to the Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems (MUSCLES) survey. The 12 stars include eight known exoplanet hosts and four stars chosen to fill out key parameter space in spectral type and rotation period. The SEDs are constructed from Hubble Space Telescope ultraviolet spectroscopy and XMM Newton, Chandra, and/or Swift X-ray observations, and completed with various model data, including Lyα reconstructions, PHOENIX optical models, APEC coronal models, and differential emission measure models in the currently-unobservable extreme ultraviolet. We provide a complete overview of the Mega-MUSCLES program, including a description of the observations, models, and SED construction. The SEDs are available as MAST high-level science products and we describe the various data products here. We also present ensemble measurements from our sample that are of particular relevance to exoplanet science, including the high-energy fluxes in the habitable zone and the far-ultraviolet to near-ultraviolet ratio. Combined with MUSCLES, Mega-MUSCLES provides SEDs covering a wide range of M dwarf spectral types and ages such that suitable proxies for any M dwarf planet host of interest may be found in our sample. However, we find that ultraviolet and X-ray fluxes can vary even between stars with similar parameters, such that observations of each exoplanet host star will remain the gold standard for interpreting exoplanet atmosphere observations.

Keywords: M dwarf stars, Ultraviolet astronomy, X-ray astronomy, Exoplanets
A Systematic Search for Candidate Supermassive Black Hole Binaries Using Periodic Mid-infrared Light Curves of Active Galactic Nuclei. Periodic variability in active galactic nuclei (AGNs) is a promising method for studying subparsec supermassive black hole binaries (SMBHBs), which are a challenging detection target. While extensive searches have been made in the optical, X-ray, and gamma-ray bands, systematic infrared (IR) studies remain limited. Using data from the Wide-field Infrared Survey Explorer (WISE), which provides unique decade-long mid-IR light curves with a six-month cadence, we have conducted the first systematic search for SMBHB candidates based on IR periodicity. Analyzing a parent sample of 48,932 objects selected from about half a million AGNs, we have identified 28 candidate periodic AGNs with periods ranging from 1268 to 2437 days (in the observer frame), by fitting their WISE light curves with sinusoidal functions. However, our mock simulation of the parent sample indicates that stochastic variability can actually produce a similar number of periodic sources, underscoring the difficulty in robustly identifying real periodic signals with WISE light curves, given their current sampling. Notably, we find no overlap between our sample and optical periodic sources, which can be explained by a distinct preference for certain periods due to selection bias. By combining archived data from different surveys, we have identified a candidate exhibiting periodic behavior in both the optical and IR bands, a phenomenon that warrants further validation through observational tests. Our results highlight the potential of IR time-domain surveys, including future missions such as the Nancy Grace Roman Space Telescope, for identifying periodic AGNs, but complementary tests are still needed to determine their physical origins, such as SMBHBs.

Keywords: Supermassive black holes, Quasars, Infrared astronomy, Active galactic nuclei, Time domain astronomy
Open Cluster Dynamics under the Influence of Outflow–Ambient Interactions. Stars with outflows impinging on ambient gas experience accelerations due to the gravitational feedback from the interaction morphology between the outflow and the ambient gas. Such "negative dynamical friction" (NDF), in contrast to the conventional "dynamical friction" (DF), is studied for its impact on the dynamics of open clusters (OCs) immersed in a uniform ambient gas. We modify the N-body integration code REBOUND with both NDF and DF implemented according to the outflow conditions of each star in a consistently constructed OC. The evolution of stars is also involved in determining the gas–star interactions throughout their stellar lives. Compared to DF-only and gas-free models with identical initial conditions, the NDF-affected cluster is puffier and evaporates faster, as indicated by various diagnostics, including lower velocity dispersions and larger half-mass and half-light radii. Neutron stars with fast winds are expelled from the cluster due to their intensive NDF effect, even without the "kicks" by asymmetric supernovae. Exploration of parameter space confirms that the NDF effect is generally enhanced with higher ambient gas densities, in qualitative agreement with the expression of acceleration. Outflow–ambient interactions should be considered for the proper interpretation of the stellar dynamics evolution in clusters.

Keywords: Neutron stars, Stellar dynamics, Stellar mass loss, Stellar winds, Open star clusters, Dynamical friction, N-body simulations
Sub-Alfvénic Turbulence: Magnetic-to-kinetic Energy Ratio, Modification of Weak Cascade, and Implications for Magnetic Field Strength Measurements. We study the properties of sub-Alfvénic magnetohydrodynamic (MHD) turbulence, i.e., turbulence with Alfvén mach number M A = V  L /V A &lt; 1, where V  L  is the velocity at the injection scale and V A is the Alfvén velocity. We demonstrate that MHD turbulence can have different properties, depending on whether it is driven by velocity or magnetic fluctuations. If the turbulence is driven by isotropic bulk forces acting upon the fluid, i.e., is velocity driven, in an incompressible conducting fluid we predict that the kinetic energy is   times larger than the energy of magnetic fluctuations. This effect arises from the long parallel wavelength tail of the forcing, which excites modes with k ∥/k ⊥ &lt; M A. We also predict that as the MHD turbulent cascade reaches the strong regime, the energy of slow modes exceeds the energy of Alfvén modes by a factor  . These effects are absent if the turbulence is driven through magnetic fluctuations at the injection scale. We confirm our predictions with numerical simulations. Since the assumption of magnetic and kinetic energy equipartition is at the core of the Davis─Chandrasekhar─Fermi (DCF) approach to measuring magnetic field strength in sub-Alfvénic turbulence, we conclude that the DCF technique is not universally applicable. In particular, we suggest that the dynamical excitation of long azimuthal wavelength modes in the galactic disk may compromise the use of the DCF technique. We discuss alternative expressions that can be used to obtain magnetic field strength from observations and consider ways of distinguishing the cases of velocity and magnetically driven turbulence using observational data.

Keywords: Interstellar magnetic fields, Magnetohydrodynamics, Astrophysical fluid dynamics, Magnetic fields
EPOCHS. IV. SED Modeling Assumptions and Their Impact on the Stellar Mass Function at 6.5 ≤ z ≤ 13.5 Using PEARLS and Public JWST Observations. We utilize deep JWST Near Infrared Camera (NIRCam) observations for the first direct constraints on the Galaxy Stellar Mass Function (GSMF) at z &gt; 10. Our EPOCHS v1 sample includes 1120 galaxy candidates at 6.5 &lt; z &lt; 13.5 taken from a consistent reduction and analysis of publicly available deep JWST NIRCam data covering the Prime Extragalactic Areas for Reionization Science, CEERS, GLASS, JADES GOOD-S, NGDEEP, and SMACS0723 surveys, totaling 187 arcmin2. We investigate the impact of spectral energy distribution fitting methods, assumed star formation histories (SFHs), dust laws, and priors on galaxy masses and the resultant GSMF. While our fiducial GSMF agrees with the literature at z &lt; 13.5, we find that the assumed SFH model has a large impact on the GSMF and stellar mass density (SMD), finding a 0.75 dex increase in the SMD at z = 10.5 between a flexible nonparametric and standard parametric SFH. Overall, we find a flatter SMD evolution at z ≥ 9 than some studies predict, suggesting a rapid buildup of stellar mass in the early Universe. We find no incompatibility between our results and those of standard cosmological models, as suggested previously, although the most massive galaxies may require a high star formation efficiency. We find that the "little red dot" galaxies dominate the z = 7 GSMF at high masses, necessitating a better understanding of the relative contributions of active galactic nucleus and stellar emission. We show that assuming a theoretically motivated top-heavy initial mass function (IMF) reduces stellar mass by 0.5 dex without affecting fit quality, but our results remain consistent with existing cosmological models with a standard IMF.

Keywords: Galaxy photometry, Galaxy counts, Galaxy masses, Lyman-break galaxies, High-redshift galaxies
The FENIKS Survey: Spectroscopic Confirmation of Massive Quiescent Galaxies at z ∼ 3─5. The measured ages of massive, quiescent galaxies at z ∼ 3─4 imply that massive galaxies quench as early as z ∼ 6. While the number of spectroscopic confirmations of quiescent galaxies at z &lt; 3 has increased over the years, there are only a handful at z &gt; 3.5. We report spectroscopic redshifts of one secure (z = 3.757) and two tentative (z = 3.336 and z = 4.673) massive ( ) quiescent galaxies with 11 hr of Keck/MOSFIRE K-band observations. Our candidates were selected from the FLAMINGOS-2 Extragalactic Near-Infrared K-band Split (FENIKS) survey, which uses deep Gemini/Flamingos-2 K  b  K  r  imaging optimized for increased sensitivity to the characteristic red colors of galaxies at z &gt; 3 with a strong Balmer/4000 Å break. The rest-frame UVJ and (ugi) s  colors of three out of four quiescent candidates are consistent with 1─2 Gyr old stellar populations. This places these galaxies as the oldest objects at these redshifts, and challenges the notion that quiescent galaxies at z &gt; 3 are all recently quenched, post-starburst galaxies. Our spectroscopy shows that the other quiescent-galaxy candidate is a broad-line active galactic nucleus (z = 3.594) with strong, redshifted Hβ + [O III] emission with a velocity offset &gt; 1000 km s−1, indicative of a powerful outflow. The star formation history of our highest redshift candidate suggests that its progenitor was already in place by z ∼ 7─11, reaching ∼1011 M ⊙ by z ≃ 8. These observations reveal the limit of what is possible with deep near-infrared photometry and targeted spectroscopy from the ground and demonstrate that secure spectroscopic confirmation of quiescent galaxies at z &gt; 4 is feasible only with JWST.

Keywords: AGN host galaxies, Quenched galaxies, Galaxy evolution, High-redshift galaxies, Post-starburst galaxies, Near infrared astronomy