adsabs/SciX_UAT_keywords huggingface dataset:
Small Region, Big Impact: Highly Anisotropic Lyman-continuum Escape from a Compact Starburst Region with Extreme Physical Properties

Extreme, young stellar populations are considered to be the primary contributor to cosmic reionization. How the Lyman continuum (LyC) escapes these galaxies remains highly elusive, and it is challenging to observe this process in actual LyC emitters without resolving the relevant physical scales. We investigate the Sunburst Arc, a strongly lensed LyC emitter at z = 2.37 that reveals an exceptionally small-scale (tens of parsecs) region of high LyC escape. The small (<100 pc) LyC-leaking region has extreme properties: a very blue UV slope (β = -2.9 ± 0.1), a high ionization state ([O III] λ5007/[O II] λ3727 = 11 ± 3 and [O III] λ5007/Hβ = 6.8 ± 0.4), strong oxygen emission (EW([O III]) = 1095 ± 40 Å), and a high Lyα escape fraction (0.3 ± 0.03), none of which are found in nonleaking regions of the galaxy. The leaking region's UV slope is consistent with approximately "pure" stellar light that is minimally contaminated by the surrounding nebular continuum emission or extinguished by dust. These results suggest a highly anisotropic LyC escape process such that LyC is produced and escapes from a small, extreme starburst region where the stellar feedback from an ionizing star cluster creates one or more "pencil-beam" channels in the surrounding gas through which LyC can directly escape. Such anisotropic escape processes imply that random sight-line effects drive the significant scatters between measurements of galaxy properties and LyC escape fraction, and that strong lensing is a critical tool for resolving the processes that regulate the ionizing budget of galaxies for reionization.

Keywords: lyman-alpha galaxies; reionization; strong gravitational lensing; emission line galaxies; starburst galaxies; galaxy structure
Galactic Settlement of Low-mass Stars as a Resolution to the Fermi Paradox

An expanding civilization could spread rapidly through the Galaxy, so the absence of extraterrestrial settlement in the solar system implies that such expansionist civilizations do not exist. This argument, often referred to as the Fermi paradox, typically assumes that expansion would proceed uniformly through the Galaxy, but not all stellar types may be equally useful for a long-lived civilization. We suggest that low-mass stars, and K-dwarf stars in particular, would be ideal migration locations for civilizations that originate in a G-dwarf system. We use a modified form of the Drake equation to show that expansion across all low-mass stars could be accomplished in 2 Gyr, which includes waiting time between expansion waves to allow for a close approach to a suitable destination star. This would require interstellar travel capabilities of no more than ~0.3 lt-yr to settle all M-dwarfs and ~2 lt-yr to settle all K-dwarfs. Even more rapid expansion could occur within 2 Myr, with travel requirements of ~10 lt-yr to settle all M-dwarfs and ~50 lt-yr to settle all K-dwarfs. The search for technosignatures in exoplanetary systems can help to place constraints on the presence of such a "low-mass Galactic Club" in the Galaxy today.

Keywords: technosignatures; astrobiology; biosignatures; search for extraterrestrial intelligence
Turbulent Structure in Supernova Remnants G46.8-0.3 and G39.2-0.3 from THOR Polarimetry

We present the continued analysis of polarization and Faraday rotation for the supernova remnants (SNRs) G46.8-0.3 and G39.2-0.3 in L-band (1-2 GHz) radio continuum in The H I/OH/Recombination line (THOR) survey. In this work, we present our investigation of Faraday depth fluctuations from angular scales comparable to the size of the SNRs down to scales less than our 16″ beam (≲0.7 pc) from Faraday dispersion (σ ϕ ). From THOR, we find median σ ϕ of 15.9 ± 3.2 rad m-2 for G46.8-0.3 and 17.6 ± 1.6 rad m-2 for G39.2-0.3. When comparing to polarization at 6 cm, we find evidence for σ ϕ ≳ 30 rad m-2 in localized regions where we detect no polarization in THOR. We combine Faraday depth dispersion with the rotation measure (RM) structure function (SF) and find evidence for a break in the SF on scales less than the THOR beam. We estimate the RM SF of the foreground interstellar medium using the SF of extragalactic radio sources and pulsars to find that the RM fluctuations we measure originate within the SNRs for all but the largest angular scales.

Keywords: interstellar medium; supernova remnants; polarimetry; radio continuum emission; interstellar magnetic fields
Transverse Vertical Oscillations During the Contraction and Expansion of Coronal Loops

In this paper, we carry out a detailed analysis of the M1.6 class eruptive flare occurring in NOAA active region 13078 on 2022 August 19. The flare is associated with a fast coronal mass ejection (CME) propagating in the southwest direction with an apparent speed of ~926 km s-1. Meanwhile, a shock wave is driven by the CME at the flank. The eruption of the CME generates an extreme-ultraviolet (EUV) wave expanding outward from the flare site with an apparent speed of ≥200 km s-1. As the EUV wave propagates eastward, it encounters and interacts with the low-lying adjacent coronal loops (ACLs), which are composed of two loops. The compression of the EUV wave results in contraction, expansion, and transverse vertical oscillations of ACLs. The commencements of contraction are sequential from western to eastern footpoints and the contraction lasts for ~15 minutes. The speeds of contraction lie in the range of 13-40 km s-1 in 171 Å and 8-54 km s-1 in 193 Å. A long, gradual expansion follows the contraction at lower speeds. Concurrent vertical oscillations are superposed on the contraction and expansion of ACLs. The oscillations last for two to nine cycles and the amplitudes are ≤4 Mm. The periods are between 3 and 12 minutes with an average value of 6.7 minutes. The results show rich dynamics of coronal loops.

Keywords: solar flares; solar oscillations
NuSTAR Observations of Candidate Subparsec Binary Supermassive Black Holes

We present an analysis of NuSTAR X-ray observations of three active galactic nuclei (AGN) that were identified as candidate subparsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey based on apparent periodicity in their optical light curves. Simulations predict that close-separation accreting SMBH binaries will have different X-ray spectra than single accreting SMBHs. We previously observed these AGN with Chandra and found no differences between their low-energy X-ray properties and the larger AGN population. However, some models predict differences to be more prominent at energies higher than probed by Chandra. We find that even at the higher energies probed by NuSTAR, the spectra of these AGN are indistinguishable from the larger AGN population. This could rule out models predicting large differences in the X-ray spectra in the NuSTAR bands. Alternatively, it might mean that these three AGN are not binary SMBHs.

Keywords: seyfert galaxies; x-ray active galactic nuclei; quasars; supermassive black holes
The Horizon Run 5 Cosmological Hydrodynamical Simulation: Probing Galaxy Formation from Kilo- to Gigaparsec Scales

Horizon Run 5 (HR5) is a cosmological hydrodynamical simulation that captures the properties of the universe on a Gpc scale while achieving a resolution of 1 kpc. Inside the simulation box, we zoom in on a high-resolution cuboid region with a volume of 1049 × 119 × 127 cMpc3. The subgrid physics chosen to model galaxy formation includes radiative heating/cooling, UV background, star formation, supernova feedback, chemical evolution tracking the enrichment of oxygen and iron, the growth of supermassive black holes, and feedback from active galactic nuclei in the form of a dual jet-heating mode. For this simulation, we implemented a hybrid MPI-OpenMP version of RAMSES, specifically targeted for modern many-core many-thread parallel architectures. In addition to the traditional simulation snapshots, lightcone data were generated on the fly. For the post-processing, we extended the friends-of-friend algorithm and developed a new galaxy finder PGalF to analyze the outputs of HR5. The simulation successfully reproduces observations, such as the cosmic star formation history and connectivity of galaxy distribution, We identify cosmological structures at a wide range of scales, from filaments with a length of several cMpc, to voids with a radius of ∼ 100 cMpc. The simulation also indicates that hydrodynamical effects on small scales impact galaxy clustering up to very large scales near and beyond the baryonic acoustic oscillation scale. Hence, caution should be taken when using that scale as a cosmic standard ruler: one needs to carefully understand the corresponding biases. The simulation is expected to be an invaluable asset for the interpretation of upcoming deep surveys of the universe.

Keywords: hydrodynamical simulations; large-scale structure of the universe; galaxy formation
The Spiral Galaxies Flat Rotational Velocity Curve Explained by the Constant Group Velocity of a Nonlinear Density Wave

The rotation velocity curves of stars in galaxies, the motions of pairs of galaxies, and the behavior of galaxies in clusters and super-clusters all indicate that there is a lack of mass on different scales in the universe. In this paper, we derive the expression for rotational velocity using the nonlinear density wave theory considering only stellar components and we show that such theory can support the observed flat rotational velocity curve due to the main property of the soliton wave, which is a constant group velocity of the wave. The surface mass density (SMD) function, used to derive gravitational potential gradient and rotational velocity, is not assumed but rather derived as a solution of the nonlinear Srödinger equation, on the contrary to the widely used, in the literature, exponential disk approximation. Three parameters relevant to the curve shape are the intensities of equilibrium SMD, the amplitude of the wave, and total angular velocity or differential rotation, equivalently. Since the shape of the rotational velocity is highly sensitive to the mentioned parameters, this theory eventually provides a method for a very accurate estimation of galaxy mass and angular velocity as well.

Keywords: spiral galaxies; galaxy rotation curves
Spin Evolution of Stellar-mass Black Holes Embedded in AGN Disks: Orbital Eccentricity Produces Retrograde Circumstellar Flows

The spin evolution of stellar-mass black holes (sBHs) embedded in AGN accretion disks is an important process relevant to the production of gravitational waves from binary BH (BBH) merger events through the AGN channel. Because embedded sBHs are surrounded by circumstellar disks (CSDs), the rotation of CSD gas flows determines the direction of the angular momentum it accretes. In this Letter, we use global 2D hydrodynamic simulations to show that while a disk-embedded sBH on a circular orbit transforms the initial retrograde Keplerian shear of the background accretion disk into a prograde CSD flow, as in the classical picture of companion-disk interaction theory, moderate orbital eccentricity could disrupt the steady-state tidal perturbation and preserve a retrograde CSD flow around the sBH. This switch in CSD orientation occurs at a transition eccentricity that scales nearly proportional to the local sound speed. This bifurcation in the CSD flow and thereafter spin-up direction of SBHs leads to the formation of a population of nearly antialigned sBHs and should be incorporated in future population models of sBH and BBH evolutions.

Keywords: galaxy accretion disks; accretion; black holes; planetary-disk interactions; gravitational wave sources
TESS Photometry of the Precataclysmic Variable Wolf 1130AB

Wolf 1130 is a triple system containing an ultramassive white dwarf (Wolf 1130B), an M subdwarf (Wolf 1130A) and a T8 subdwarf (Wolf 1130C). We set out to determine a precise mass for Wolf 1130B by phase-folding TESS photometry to the previously reported orbital period. Each orbit was fit for ellipsoidal, Doppler beaming, and thermal photometric variability. We found that the measured beaming amplitude of Wolf 1130AB is nearly triple the theoretical expectation, which we assign to the short-wavelength filter cutoff of TESS and features in the M subdwarf spectrum. The photometric amplitudes suggest inflation of Wolf 1130A by as much as 20%, possibly due to its rapid rotation under tidal locking. TESS photometry can be used to obtain masses for short-period binary systems, but photometric precision limits the utility in the case of Wolf 1130AB.

Keywords: close binary stars; cataclysmic variable stars; subdwarf stars; photometry; white dwarf stars; m dwarf stars
ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): A Hot Corino Survey toward Protostellar Cores in the Orion Cloud

The presence of complex organic molecules (COMs) in the interstellar medium is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All of the hot corino sources discovered are likely Class 0, and their sizes of the warm region (>100 K) are comparable to 100 au. The luminosity of the hot corino sources exhibits positive correlations with the total number of methanol and the extent of its emissions. Such correlations are consistent with the thermal desorption picture for the presence of hot corinos and suggest that the lower-luminosity (Class 0) sources likely have a smaller region with COM emissions. With the same sample selection method and detection criteria being applied, the detection rates of the warm methanol in the Orion cloud (15/37) and the Perseus cloud (28/50) are statistically similar when the cloud distances and the limited sample size are considered. Observing the same set of COM transitions will bring a more informative comparison between the cloud properties.

Keywords: astrochemistry; interstellar molecules; star forming regions; low mass stars; protostars
The Visual Lightcurve of Comet C/1995 O1 (Hale-Bopp) from 1995 to 1999

The great comet C/1995 O1 (Hale-Bopp) presented a remarkable opportunity to study its long-term brightness over four years. We used 2240 observations published in the International Comet Quarterly from 17 observers during 1995 July to 1999 September to create a secular lightcurve. In order to account for observer differences, we present a novel algorithm to reduce scatter and increase precision in a lightcurve compiled from many sources. It is implemented in a publicly available code, ICQSPLITTER, which uses a self-consistent statistical approach. To first order, the comet's lightcurve approximates an r-4 response for both pre- and postperihelion distances. The preperihelion data are better fit with a fifth-order polynomial with inflection points at 4.0, 2.6, 2.1, and 1.1 au, some of which are associated with physical changes in the coma. Outbursts may have occurred a few days before perihelion and at ∼2.2 and 7.4 au postperihelion. The Afρ values derived from the final magnitudes are consistent with an r-1.5 dependence on heliocentric distance and are within a factor of 2-4 of those derived from spectroscopy and narrowband photometry. We present correlation equations for visual magnitudes and CO and H2O production rates that are consistent with the preperihelion brightness increasing due to CO outgassing until about 2.6-3.0 au from the Sun and then are strongly correlated with H2O production rates. We also present two generalized correlation equations that may be useful for observation planning and data analysis with the James Webb Space Telescope and other observatories.

Keywords: comets; long period comets; coma dust; astrostatistics; light curves; visual observation; comae
A Silent Revolution in Fundamental Astrophysics

Arbitrariness in the zeropoint of bolometric corrections is a paradigm that is nearly a century old and leads to two more paradigms. "Bolometric corrections must always be negative," and "the bolometric magnitude of a star ought to be brighter than its V magnitude". Both were considered valid before the IAU 2015 General Assembly Resolution B2, a revolutionary document that supersedes all three aforementioned paradigms. The purpose of this article is to initiate new insight into and a new understanding of the fundamental astrophysics and present new capabilities to obtain standard and more accurate stellar luminosities and gain more from accurate observations in the era after Gaia. The accuracy gained will aid in advancing stellar structure and evolution theories and also Galactic and extragalactic research, observational cosmology, and searches for dark matter and dark energy.

Keywords: stellar physics
Formation of Dust Clumps with Sub-Jupiter Mass and Cold Shadowed Region in Gravitationally Unstable Disk around Class 0/I Protostar in L1527 IRS

We have investigated the protostellar disk around a Class 0/I protostar, L1527 IRS, using multiwavelength observations of the dust continuum emission at λ = 0.87, 2.1, 3.3, and 6.8 mm, obtained by the Atacama Large Millimeter/submillimeter Array and the Jansky Very Large Array (VLA). Our observations achieved a spatial resolution of 3-13 au and revealed an edge-on disk structure with a size of ~80-100 au. The emission at 0.87 and 2.1 mm is found to be optically thick, within a projected disk radius of r proj ≲ 50 au. The emission at 3.3 and 6.8 mm shows that the power-law index of the dust opacity (β) is β ~ 1.7 around r proj ~ 50 au, suggesting that grain growth has not yet begun. The dust temperature (T dust) shows a steep decrease with T dust ∝ r proj -2 outside the VLA clumps previously identified at r proj ~ 20 au. Furthermore, the disk is gravitationally unstable at r proj ~ 20 au, as indicated by a Toomre Q parameter value of Q ≲ 1.0. These results suggest that the VLA clumps are formed via gravitational instability, which creates a shadow on the outside of the substructure, resulting in the sudden drop in temperature. The derived dust masses for the VLA clumps are ≳0.1 M J. Thus, we suggest that Class 0/I disks can be massive enough to be gravitationally unstable, which may be the origin of gas giant planets in a 20 au radius. Furthermore, the protostellar disks could be cold due to shadowing.

Keywords: protostars; planet formation; circumstellar disks; interstellar medium; young stellar objects; dust continuum emission; star formation
Examining the Source Regions of Solar Energetic Particles Using an AI-generated Synchronic Potential Field Source Surface Model

We study the source regions of six solar energetic particle (SEP) events accelerated near or behind the limbs of the Sun. We use AI-generated farside magnetograms at a near real-time basis developed by Jeong et al. and AIHMI-PFSS extrapolations up to 2.5R ⊙ computed using the input of the synchronic data combining AI-generated farside and HMI magnetograms. By comparing the AIHMI, HMI, Global Oscillations Network Group (GONG) synoptic magnetograms, and Air force Data Assimilative Photospheric flux Transport synchronic magnetograms, as well as the PFSS extrapolations, we find interesting differences between them in view of SEP source regions and magnetic field configurations. First, the structures and sizes of the source active regions (ARs) are changed. The total unsigned magnetic field fluxes of the ARs are mostly stronger in the AIHMI than in the HMI and GONG magnetograms. Second, newly emerging ARs are observed in the SEP source regions in the AIHMI magnetograms for two events. Third, the alterations in the magnetic flux, the emergence, and the dissipation of ARs lead to modifications in the locations of the global polarity inversion lines (PILs). The EUV wave propagation is typically observed to be oriented nearly perpendicular with respect to the local PIL, suggesting that the AIHMI-PFSS extrapolations around the source region are more realistic. This study shows that the continuous farside evolution of AR magnetic fields, which is accomplished by our AI synchronic magnetograms, can lead to an improved understanding of SEP source ARs.

Keywords: solar energetic particles; solar magnetic fields; convolutional neural networks; solar flares; solar coronal mass ejections
On the Interaction of a Bonnor-Ebert Sphere with a Stellar Wind

The structure of protostellar cores can often be approximated by isothermal Bonnor-Ebert spheres (BES), which are stabilized by an external pressure. For the typical pressure of 104kB K cm-3 to 105kB K cm-3 found in molecular clouds, cores with masses below 1.5 M⊙ are stable against gravitational collapse. In this paper, we analyze the efficiency of triggering gravitational collapse with a nearby stellar wind, which represents an interesting scenario for triggering low-mass star formation. We analytically derive a new stability criterion for a BES compressed by a stellar wind, which depends on its initial nondimensional radius ${\xi }_{\max }$ . If the stability limit is violated the wind triggers a core collapse. Otherwise, the core is destroyed by the wind. We estimate its validity range to $2.5\lt {\xi }_{\max }\lt 4.2$ and confirm this in simulations with the SPH-Code GADGET-3. The efficiency of triggering a gravitational collapse strongly decreases for ${\xi }_{\max }\lt 2.5$ since in this case destruction and acceleration of the whole sphere begin to dominate. We were unable to trigger a collapse for ${\xi }_{\max }\lt 2$ , which leads to the conclusion that a stellar wind can move the smallest unstable stellar mass to 0.5 M⊙ and that destabilizing even smaller cores would require external pressure larger than 105kB K cm-3. For ${\xi }_{\max }\gt 4.2$ the expected wind strength according to our criterion is small enough that the compression is slower than the sound speed of the BES and sound waves can be triggered. In this case our criterion somewhat underestimates the onset of collapse and detailed numerical analyses are required.

Keywords: star formation
Magnetoacoustic Waves in a Magnetic Slab Embedded in an Asymmetric Magnetic Environment. III. Applications to the Solar Atmosphere

Analytical and numerical modeling of the behavior of magnetohydrodynamic waves in various magnetic geometries can offer a valuable contribution to the field of solar magnetoseismology. Based on analytical results from our previous studies, here we illustrate a few solar applications of these findings concerning the propagation of magnetoacoustic waves in a magnetic slab embedded in an asymmetric environment. Bearing in mind the simplifying assumptions made, this asymmetric model incorporating external magnetic fields can be used to describe a wide variety of multilayered solar features, some of which are observable and have already been studied in solar structures. Specific potential applications are: prominences, polar plumes and their environment, magnetic bright points, and light bridges, as well as adjacent large-scale layers in the solar atmosphere (e.g., the photosphere—interface region—corona triad, or the chromosphere—transition region—corona group). In these individual cases, the appropriate dispersion relations are derived and solved. The obtained wave propagation solutions may serve (i) not just as impetus to be confirmed by high-resolution observations but (ii) also to be exploited for further diagnostic purposes by solar magnetoseismology of these frequently studied magnetic structures.

Keywords: the sun; magnetohydrodynamics; solar atmosphere; solar prominences; solar magnetic bright points; sunspots