Sazuna/UAT_keywords huggingface dataset:
GMCs and Star Formation in Galaxies. I. Mass Loss from a GMC Induced by an H II Region. The destruction of giant molecular clouds (GMCs) is a key component in galaxy evolution. We theoretically model the destruction of GMCs by H II regions, which evaporate ionized gas and eject neutral gas during their expansion. H II regions follow one of three tracks, depending on the extreme-UV luminosity, S, of the ionizing OB association: the expansion can stall inside the cloud; it can break out, forming a blister (champagne) flow; or, for S &gt; Scom, it can result in the formation of a cometary cloud. We present results for the accumulated mass loss, Mloss(t), and the final mass loss, Mloss,f, by evaporation and ejection for a range of cloud masses (104 &lt; M &lt; 107 M⊙), cloud surface densities (50 &lt; Σ &lt; 1000 M⊙ pc−2), OB association luminosities (1044 &lt; S &lt; 1052 s−1), and off-center position of the association. We do not consider starbursts; our neglect of radiation pressure restricts our treatment to  S&lt;1052[(M/106M⊙)0.3/(Σ/100M⊙pc−2)] s-1, and our neglect of gravity restricts (M/106 M⊙)(Σ/100 M⊙ pc−2) ≲ 10. We find that Mloss,f for the range 0.1 ≲ Mloss,f/M ≲ 0.7, is proportional to Sp, where p ∼ 0.45─0.75 depends on M, Σ, and association position. We find analytic fits to Scom as a function of Σ, M, and association position. S &gt; Scom associations destroy at least 70% of the initial cloud. We find a critical cloud mass Msurvive above which clouds never become cometary and lose ≲70% of their mass via a single association. Low-mass clouds mostly lose mass via ejection of neutral gas.

Keywords: Giant molecular clouds, Galaxy evolution, Interstellar medium, Milky Way evolution, H II regions
What You See Is What You Get: Empirically Measured Bolometric Luminosities of Little Red Dots. New populations of red active galactic nuclei (known as "little red dots") discovered by JWST exhibit remarkable spectral energy distributions. Leveraging X-ray through far-infrared observations of two of the most luminous known little red dots, we directly measure their bolometric luminosities. We find evidence that more than half of the bolometric luminosity likely emerges in the rest-frame optical, with Lbol/L5100 = 5, roughly half the value for "standard" active galactic nuclei. Meanwhile, the X-ray emitting corona, UV-emitting blackbody, and reprocessed mid to far-infrared emission are all considerably subdominant, assuming that the far-infrared luminosity is well below current measured limits. We present new bolometric corrections that dramatically lower inferred bolometric luminosities by a factor of 10 compared to published values in the literature. These bolometric corrections are in accord with expectations from models in which gas absorption and reprocessing are responsible for the red rest-frame optical colors of little red dots. We discuss how this lowered luminosity scale suggests a lower mass scale for the population by at least an order of magnitude (e.g., ∼105─107 M⊙ black holes, and ∼108 M⊙ galaxies), alleviating tensions with clustering, overmassive black holes, and the integrated black hole mass density in the Universe.

Keywords: Supermassive black holes, Active galactic nuclei, High-redshift galaxies
Jellyfish Galaxies in Magnetic Fields: Insights from Numerical Simulations. Jellyfish galaxies provide direct evidence of ram pressure stripping in cluster environments. We investigate the role of magnetic fields in the formation of jellyfish galaxies with a multiphase interstellar medium (ISM) using radiation magnetohydrodynamic simulations. We impose magnetized (magnetohydrodynamic; MHD) and nonmagnetized (hydrodynamic; HD) winds on the gas-rich dwarf galaxies containing the magnetized or nonmagnetized ISM. The MHD winds strip the disk gas more effectively than the HD winds because of the magnetic force acting against the local density gradient, which results in remarkably different ram pressure stripped features. The magnetic fields induced by the MHD winds generate a strong magnetic pressure, which forms smoothed disks and tail gas features. Since the stripped ISM in MHD wind cases travels while being nearly isolated from the intracluster medium (ICM), the stripped ISM mostly forms stars within 20 kpc of the galactic disks. In contrast, nonmagnetized winds facilitate the efficient mixing of the stripped ISM with the ICM, resulting in the formation of abundant warm clouds that cool and collapse in the distant (∼50─100 kpc) tails at times of a few hundred Myr. Consequently, distant tail star formation occurs only in the HD wind runs. Finally, despite the different tail features, the star formation rates in the disk remain similar owing to the interplay between the increased gas stripping and the gas density increase in the disks of the MHD wind runs. These results suggest that the magnetized ICM may have a significant influence on jellyfish galaxies, whereas the magnetized ISM play a minor role.

Keywords: Radiative magnetohydrodynamics, Ram pressure stripped tails, Galaxy environments
Turbulent Energy Cascade Rate in the Magnetic Reconnection Exhaust in the Solar Wind. The turbulent energy cascade rate in the inertial range has been extensively studied in various space plasma environments, including the solar wind, and Earth's magnetosheath and magnetotail. However, the energy cascade rate in the magnetic reconnection exhaust in the solar wind remains unexplored. Here, we present the first investigation of the energy cascade rate in the solar wind magnetic reconnection exhausts using high-resolution data from the Wind spacecraft. Analyzing 79 solar wind reconnection events observed at 1 au, we compute the energy cascade rate for each event utilizing both incompressible and compressible magnetohydrodynamic turbulence models. Our results reveal that the energy cascade rate across the inertial range in the exhaust reaches ~104 J kg−1 s−1, roughly 1 order of magnitude higher than in the nonreconnection region in the solar wind. Furthermore, we find that the energy cascade rate in the exhaust exhibits a strong correlation with the outflow velocity. These findings advance our understanding of turbulent energy transfer in the solar wind turbulence and provide new insights into the dynamics of space plasmas.

Keywords: Interplanetary turbulence, Solar wind, Solar magnetic reconnection
Exoplanets beyond the Conservative Habitable Zone. I. Habitability. The Habitable Zone (HZ) is defined by the possibility of sustaining liquid water on a planetary surface. In the solar system, the HZ for a conservative climate model extends approximately between the orbits of Earth and Mars. We elaborate on earlier HZ models and apply an analytical climate model of the temperature distribution on tidally locked planets to extend the HZ. We show that planets orbiting M- and K-dwarf stars may maintain liquid water on their night side, significantly closer to their host star than the inner border of the conservative HZ. We calculate the extended borders of the HZ in the flux─effective temperature diagram. This extension may explain the presence of water vapor and other volatile gases in the transmission spectra of warm Super-Earth-sized exoplanets closely orbiting M dwarfs, recently detected by JWST. We also mention the HZ extension outward, due to subglacial liquid water in the form of intraglacial lakes or subglacial melting.

Keywords: M dwarf stars, Exoplanets, Greenhouse effect, Tidal radius, Astrobiology, Biosignatures, Habitable zone, Habitable planets, Exoplanet atmospheres
Exoplanets beyond the Conservative Habitable Zone. II. Occurrence. We show that the extension of the habitable zone (HZ) due to the presence of liquid water on the nightside of tidally locked planets, calculated in earlier works, significantly increases the number of potentially habitable planets. We calculate the occurrence of habitable planets orbiting M-, K-, and G-dwarf stars within the conservative and extended HZ, beyond the inner and outer boundaries of the conservative HZ. Integrating over the phase space in the HZ diagram and normalizing our calculation to a relatively recent analysis of the Kepler data, we show that potentially habitable planets may be as much as 50 times more abundant than in the most conservative estimate, limited to the conservative HZ of G-type stars only. We find that the extended HZ could imply more than one habitable planet per star, and hundreds of habitable planets within 10 pc from Earth.

Keywords: M dwarf stars, Extrasolar rocky planets, Exoplanets, Planetary climates, Habitable zone, Habitable planets
Temporary Equilibrium Mass Transfer Rate in Cataclysmic Variables?. The separation of a binary system increases or decreases over time, governed by angular momentum (AM) changes. In cataclysmic variables (CVs), Roche-lobe overflow from the red dwarf (RD) to the white dwarf (WD) redistributes AM within the system through conservative mass transfer, modifying the separation. Moreover, angular momentum loss (AML) arises from magnetic braking by the RD and gravitational radiation from the binary's orbit. These three primary mechanisms have competing effects on the separation, which is correlated with the mass transfer rate. Long-term simulations show that the intereruption mass transfer rate gradually increases toward a nova eruption, and also evolves over the CV's lifetime, strongly depending on the RD mass. This work explores the limits of stellar mass combinations in CVs and derives theoretical (sometimes hypothetical) accretion rates at which the three mechanisms cancel each other out, yielding an equilibrium accretion rate that, if a given system were to reach it, would be maintained until the next nova eruption. These values are roughly 10−11─10−10M⊙ yr−1 for fully convective RDs (≲0.35M⊙) independent of the WD mass and weakly dependent on the RD mass, while for RD masses of ≳0.35M⊙the equilibrium accretion rate is at least ∼10−9M⊙ yr−1 and dependent on the WD and RD masses—decreasing with the increase of the former and the decrease of the latter. The equilibrium accretion rate serves as a tool to calculate a lower limit to the system's recurrence period, based only on the WD mass and orbital period, which are typically determined observationally.

Keywords: Accretion, Close binary stars, Roche lobe overflow, Novae, Recurrent novae, Cataclysmic variable stars
A "Valley" in Heliospheric Energetic Particle Intensities and Implications for a New Horizons Encounter with the Solar Wind Termination Shock. We analyze ∼40─200 keV energetic particle observations from the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) on board the New Horizons (NH) spacecraft from 2007 to 2024 and compare them with similar measurements from the Low Energy Charged Particle experiments on the Voyager 1 and Voyager 2 spacecraft when they were at comparable heliocentric distances (5─60 au). In both Voyager data sets, particle intensities generally decrease with increasing radial distance from the Sun, reaching a minimum in the outer heliosphere before rising again prior to their respective encounters with the heliospheric termination shock (TS). This radial behavior in the intensity-time profiles is described as a heliospheric valley. The NH/PEPSSI time series from 5 au (2007) to 60 au (2024) exhibits a similar decrease in particle fluxes with distance. Analysis of the radial dependence of energetic particle intensities from all three spacecraft normalized by observations at 1 au to account for the solar cycle effects reveals an approximate piece-wise composite power-law relationship, with a slope break (steeper decline) beyond ∼33 au. This break may reflect differences in the dominant transport and acceleration mechanisms operating in the two regions demarcated by this radial break. In addition, a radial scaling method is applied to Voyager observations to best match the NH data. This comparison provides an estimate for the NH TS crossing between 2027 (68 au) and 2034 (83 au).

Keywords: Solar energetic particles, Termination shock, Heliosphere
Refined Classification of Young Stellar Objects and Asymptotic Giant Branch Stars by Infrared Magnitudes, Colors, and Time-domain Analysis with Machine Learning. We introduce a binary classification model, the double filter model, utilizing various machine learning and deep learning methods to classify young stellar objects (YSOs) and asymptotic giant branch (AGB) stars. Since YSOs and AGB stars share similar infrared (IR) photometric characteristics due to comparable temperatures and the presence of circumstellar dust, distinguishing them is challenging and often leads to misclassification. While machine learning and deep learning techniques have helped reduce YSO─AGB misclassifications, achieving a reliable separation remains challenging. Given that YSOs and AGB stars exhibit distinct light curves resulting from different variability mechanisms, our double filter model leverages light-curve data to enhance classification accuracy. This approach uncovered YSOs and AGB stars that were misclassified in IR photometry, and was validated against Taurus YSOs and spectroscopically confirmed AGB stars. We applied the model to the Spitzer/IRAC Candidate YSO catalog for the inner Galactic midplane for catalog refinement and identified potential AGB star contaminants.

Keywords: Young stellar objects, Classification, Asymptotic giant branch, Near infrared astronomy
Prospects for Identifying Pulsar Candidates in Radio Surveys Using Scintillation. In our previous paper, we developed a technique for identifying pulsar candidates in interferometric radio images using their distinctive scintillation signatures. Building on this technique, the present study simulates a pulsar population using the PsrPopPy Python module to investigate the technique's limitations and detection capabilities. Among pulsars detectable exclusively by this technique, 50% have duty cycles exceeding the mean value of 0.09 observed in time-domain detections. Our pulsar population simulations revealed a set of observational parameters that optimize pulsar detection. An observation frequency of 1420 MHz and a channel width of 10 kHz emerge as the optimal configuration to maximize the pulsar detection efficiency. By applying a scintillation-based technique to future radio telescopes like DSA-2000, we can detect 56% of normal pulsars and 84% of MSPs in addition to those detected using nonimaging, time-domain surveys. These detected pulsars cannot be verified by time-domain searches.

Keywords: Astronomical simulations, Interstellar scintillation, Radio pulsars
Generalized Bondi Accretion Flow with and without Outflow. The properties of accretion flows are affected by the angular momentum of the accreting gas. M.-G. Park found that the mass accretion rate, specifically, decreases significantly as the gas angular momentum increases. However, R. Narayan &amp; A. C. Fabian found the decrease modest. We investigate global solutions for rotating polytropic flows in a much wider parameter space to understand their general properties within the slim disk approximation and a viscosity description suitable for both low- and high-angular-momentum flows. We find that the mass accretion rate for flows with a small Bondi radius decreases steeply as the gas angular momentum increases, while for those with a large Bondi radius, it decreases gradually. Therefore, the decrease of mass accretion rate due to gas rotation can be significant or mild depending on the Bondi radius. We further investigate global solutions of accretion with outflows using the ADIOS model of R. D. Blandford &amp; M. C. Begelman. Stronger outflows in general slightly increase the mass inflow rate at the outer boundary, but the actual mass accreted into the black hole decreases by orders of magnitude. Stronger outflows also weaken the dependence of the mass accretion rate on the gas angular momentum when the viscosity parameter α is small. The intricate dependence of the mass inflow rate at the outer boundary and the mass accretion rate into the black hole on gas angular momentum will have interesting implications for the growth of black holes and their energy output.

Keywords: Accretion, Black hole physics, Bondi accretion, Black holes
A Turbulent Framework for Star Formation in High-redshift Galaxies. Observations of distant galaxies suggest that the physics of galaxy formation at high redshifts differs significantly from later times. In contrast to large, steady disk galaxies like the Milky Way, high-redshift galaxies are often characterized by clumpy, disturbed morphologies and bursty star formation histories. These differences between low-mass, bursty galaxies and higher-mass, steady star-forming galaxies have recently been studied in galaxy formation simulations with resolved multiphase interstellar medium (ISM). These simulation studies indicate that while steady disk galaxies can be well-modeled as "equilibrium disks" embedded in a distinct, hot circumgalactic medium (CGM), bursty galaxies are much more dynamic and their star formation occurs in a dispersion-dominated medium that extends to halo scales, with no clear boundary between the ISM and the CGM. We develop an analytic framework to model star formation in bursty galaxies that are not adequately modeled as equilibrium disks. The framework approximates the gas in low-mass halos as a continuous, supersonically turbulent medium with large density fluctuations. Star formation occurs locally in the high-density tail of a roughly log-normal density distribution. This is analogous to turbulent models of star formation in molecular clouds, but here applied on inner CGM scales. By comparing with galaxy formation simulations from the Feedback in Realistic Environments project, we show that this framework can be used to understand star formation efficiencies (SFEs) and radial profiles in halos. The turbulent framework shows explicitly how the instantaneous galaxy-averaged SFE can be relatively low even if the local efficiency in dense gas approaches unity.

Keywords: Hydrodynamical simulations, Galaxy formation, Theoretical models, Star formation, Interstellar medium, Circumgalactic medium, High-redshift galaxies
Magnetic Reconnection Energy Fluxes in the Near-Sun Heliospheric Current Sheet as Observed by Parker Solar Probe. The Heliospheric Current Sheet (HCS) is a fundamental feature of the heliosphere, playing a key role organizing the magnetic structure of the solar wind. In contrast to observations previously made through the majority of the heliosphere, Parker Solar Probe has recently revealed that the HCS is typically reconnecting in the inner heliosphere. This provides a new opportunity to study reconnection dynamics in large-scale current sheets and assess how this is different from smaller systems such as Earth's magnetosphere. We use Parker data to explore HCS reconnection energy partition in two case studies from Encounter 07 and 08. In both cases, we find that in the exhaust, the proton enthalpy flux density is largest, with significant contributions from the proton kinetic energy flux density and electron enthalpy flux density. In contrast, the exhaust Poynting flux density is small in both events. The size and stability of the HCS allows for a control volume analysis to be performed, thus allowing us to estimate changes in energy flux during reconnection. This analysis shows that energy is primarily transferred from the magnetic field to the protons, manifested as the kinetic energy of the exhaust and proton heating. Although the exhaust electron enthalpy flux density is significant, the incoming and outgoing electron enthalpy fluxes are found to be similar, and there is minimal electron heating. The small contribution of the Poynting flux in the outflow may be an important feature of HCS reconnection, with implications for reconnection in large-scale solar and astrophysical current sheets more generally.

Keywords: Space plasmas, Solar wind, Solar magnetic reconnection, Plasma physics
Accretion from a Shock-inflated Companion: Spinning Down Neutron Stars to Hour-long Periods. Recent observations have unveiled a population of pulsars with spin periods of a few minutes to hours that lie beyond the traditional "death line." If they originate from neutron stars (NSs), the existence of such ultralong-period pulsars (ULPs) challenges our current understanding of NS evolution and emission. In this work, we propose a new channel for disk formation based on NSs born in close binaries with main-sequence companion stars. Using a hydrodynamic simulation of supernova─companion interactions, we show that a newborn NS may gravitationally capture gas as it moves through the complex density field shaped by the explosion. For a binary separation of 20 R⊙and a companion mass of 4 M⊙, we find the occurrence fraction for disk formation around unbound NSs to be ∼10%. By modeling the disk evolution and its interaction with the NS, we find a bimodal distribution in spin periods: canonical pulsars with P ≲ 10 s are the ones who lack disks or whose magnetospheres never interacted with the disk, and ULPs with 103 ≲ P &lt; 105 s are produced when the system undergoes a short-lived "propeller" phase during which the NS undergoes rapid spin-down. Such ULPs are formed under strong initial dipolar magnetic field strengths B0 ≳ 1014 G, with a formation rate of 10−4 yr−1 in the Milky Way. We also find that a small population of pulsars with moderate magnetic field strengths (1013 ≲ B0 ≲ 1014 G) and relatively slow initial periods (P0 ≳ 0.1 s) evolve to P ∼ 102 s, filling the gap between the bimodal distribution. Thus, our model provides a unified explanation for pulsar spins beyond the death line.

Keywords: Radio transient sources, Stellar accretion disks, Binary stars, Pulsars
Accretion Regimes of Neutrino-cooled Flows onto Black Holes. Neutrino-cooled accretion disks can form in the aftermath of neutron-star mergers as well as during the collapse of rapidly rotating massive stars and the accretion-induced collapse of rapidly rotating white dwarfs. Due to Pauli blocking as electrons become degenerate at sufficiently high accretion rates  Ṁ , the resulting neutronization of the dissociated accreting plasma makes these astrophysical systems promising sources of rapid neutron-capture nucleosynthesis (the r-process). We present a one-dimensional, general-relativistic, viscous-hydrodynamic model of neutrino-cooled accretion disks around black holes. With collapsars, supercollapsars, and very massive star collapse in mind, we chart the composition of the accretion flow and systematically explore different radiatively efficient and inefficient accretion regimes with increasing  Ṁ , across a vast parameter space of  Ṁ∼10−6−106M⊙s−1 , black hole masses of M∙ ∼ 1─104M⊙, and dimensionless spins of χ∙ ∈ [0, 1), as well as α-viscosity values of α ∼ 10−3─1. We show that these accretion regimes are separated by characteristic thresholds  Ṁchar  that follow power laws  Ṁchar∝M∙ααβ  and that can be understood based on analytic approximations we derive. We find that outflows from such disks are promising sites for r-process nucleosynthesis up to M∙ ≲ 3000M⊙. These give rise to lanthanide-bearing "red" super-kilonovae transients mostly for M∙ ≲ 200─500M⊙ and lanthanide-suppressed "blue" super-kilonovae for larger M∙. Proton-rich outflows can develop specifically for large black hole masses (M∙ ≳ 100M⊙) in certain accretion regimes, which may give rise to proton-rich isotopes via the neutrino-induced proton-capture process (the νp-process).

Keywords: Black holes, Nucleosynthesis, R-process, Compact objects, Stellar accretion disks