Sazuna/UAT_keywords huggingface dataset:
Modeling the "Dark-matter Dominated" Dwarf Galaxy Segue 1 with a Supermassive Black Hole. The dwarf spheroidal galaxy, Segue 1, is thought to have one of the largest ratios of dark matter to stellar mass. Using orbit-based dynamical models, we model Segue 1, including a dark halo and a central black hole. The best-fit model requires a black hole mass of 4.5 ± 1.5 × 105 M⊙. The value of the black hole mass is similar either with or without a dark halo. The mass-to-light ratio of the stars is poorly constrained by the dynamical modeling, reflecting that Segue 1 is dominated by mass other than stars. Dynamical models that exclude a black hole provide a worse fit and require a dark halo with very-small-scale radii of below 100 pc. Additionally, the zero black hole models require a stellar orbital distribution that is highly radially biased. The model with a black hole provides an orbital structure that is close to isotropic, more similar to other well-studied systems. We argue that the two-parameter models of stars and black hole provide a better description of Segue 1 than the three-parameter models of stars and two dark halo components. Additional support for a central black hole comes from a significant increase in the central rotation. Using individual velocities, we measure a rotation amplitude of 9.0 ± 2.4 km s−1. Segue 1 is likely being tidally stripped at large radii, and we might be witnessing the remnant nucleus of a more massive system. Alternatively, given the high black hole mass relative to the stellar mass, Segue 1 is analogous to the Little Red Dots seen in the early Universe.

Keywords: Black holes
Resolving Black Hole Family Issues among the Massive Ancestors of Very High-spin Gravitational-wave Events like GW231123. The latest detection of GW231123, a black hole (BH) merger with exceptionally large component masses and high spins, has been suggested as a smoking gun for hierarchical formation. In this scenario, a first generation of BHs form from collapsing stars in dense environments such as star clusters, where they assemble dynamically and undergo subsequent mergers. We discuss three challenges for forming GW231123-like events in this scenario: (1) The high masses of the incoming BHs appear to be in the predicted pair-instability mass gap, suggesting that higher-order generation BHs are involved. (2) Very high spins (χf ≳ 0.8) are unlikely for dynamically assembled BHs because of the isotropic spin distribution. (3) Hierarchically formed BHs can receive large recoils that kick them out of their cluster and prohibit subsequent mergers. We simulate this scenario and show that only a few percent of mergers recover remnants within GW231123's primary spin estimate  χ1=0.9−0.19+0.10  and are retained inside typical star clusters. A large fraction of very rapidly spinning second-generation BHs (including χf ≳ 0.9) can form if the first-generation BHs merge with aligned spins. This is a natural outcome of massive binary star evolution scenarios, such as a chemically homogeneous evolution. This scenario also predicts equal masses for the components, implying that the resulting BHs receive low recoil kicks (vk ≲ 100 km s−1) and would therefore likely be retained inside a cluster. GW231123-like events, if formed in a star cluster, could require first-generation BHs with aligned spins formed from interacting stellar binaries, followed by the dynamical assembly for a subsequent merger.

Keywords: Binary stars, Black holes, Interacting binary stars, Gravitational wave sources, Gravitational waves, Astrophysical black holes, Star clusters
Insights for Early Massive Black Hole Growth from JWST Detection of the [Ne v] λ3427 Emission Line. We use the narrow [Ne v] λ3427 emission line detected in the recently published JWST spectra of two galaxies, at z ≃ 6.9 and 5.6, to study the key properties of the active galactic nuclei (AGN) and the supermassive black holes (SMBHs) in their centers. Using a new empirical scaling linking the  NeV  line emission with AGN accretion-driven (continuum) emission, derived from a highly complete low-redshift AGN sample, we show that the  NeV  emission in the two z &gt; 5 galaxies implies total (bolometric) AGN luminosities of order Lbol ≍ (4─8) × 1045 erg s−1. Assuming that the radiation emitted from these systems is Eddington limited, the (minimal) black hole (BH) masses are of order MBH ≳ 107 M⊙. Combined with the published stellar masses of the galaxies, estimated from dedicated fitting of their spectral energy distributions, the implied BH-to-stellar mass ratios are of order MBH/Mhost ≍ 0.1─1. This is considerably higher than what is found in the local Universe, but is consistent with the general trend seen in some other z ≳ 5 AGN. Given the intrinsic weakness of the  NeV  line and the nature of the  NeV ─to─Lbol scaling, any (rare) detection of the [Ne v] λ3427 line at z &gt; 5 would translate to similarly high AGN luminosities and SMBH masses, thus providing a unique observational path for studying luminous AGN well into the epoch of reionization, including obscured sources.

Keywords: AGN host galaxies, Supermassive black holes, Active galactic nuclei, High-redshift galaxies
Energy Cascade and Damping in Fast-mode Compressible Turbulence. Compressible turbulence governs energy transfer across scales in space and astrophysical systems. Capturing both the turbulence cascade and damping is therefore crucial for models of energy conversion, plasma heating, and particle transport in diverse plasma environments, but it remains challenging. Progress is constrained by two unresolved fundamental questions: the persistence of the turbulence cascade in the presence of shocks and discontinuities, and the validity of classical wave theories under strong nonlinearity. In particular, it remains unclear whether meaningful cascade dynamics can be defined in compressible turbulence with phase steepening and whether frameworks developed for monochromatic waves remain applicable to complex, broadband fluctuations. Using large-scale, high-resolution kinetic simulations, we analyze turbulence─particle interactions, which are beyond the capability of standard magnetohydrodynamic (MHD) simulations. We show that compressible turbulence damping at MHD scales is in quantitative agreement with transit-time damping theory, even in fully developed nonlinear states. Moreover, the cascade persists despite the generation of shocks and discontinuities due to phase steepening, revealing a surprising robustness of cross-scale energy transfer under extreme conditions. We further provide the spectral expression of compressible turbulence. These results close a long-standing gap in the physics of compressible turbulence and establish a robust foundation for turbulence modeling from the heliosphere to galaxies.

Keywords: Interplanetary turbulence, Magnetohydrodynamics, Plasma physics, Interstellar plasma
Extreme Negative Polarization of New Interstellar Comet 3I/ATLAS. We present the first polarimetric observations of the third discovered interstellar object (ISO), 3I/ATLAS (C/2025 N1, or 3I), obtained preperihelion with FORS2 at the Very Large Telescope, ALFOSC at the Nordic Optical Telescope, and FoReRo2 at the 2 m Ritchey-Chrétien-Coudé telescope, over a phase angle range of 7 .° 7─22 .° 4. This marks the second-ever polarimetric study of an ISO, the first distinguishing 2I/Borisov from most solar system comets by its higher positive polarization. Our polarimetric measurements as a function of phase angle reveal that 3I is characterized by a deep and narrow negative polarization branch, reaching a minimum value of −2.7% at phase angle 7∘, and an inversion angle of 17∘—a combination unprecedented among asteroids and comets, including 2I/Borisov. At very small phase angles, the extrapolated slope of the polarization phase curve is consistent with that of certain small trans-Neptunian objects and Centaur Pholus, consistent with independent spectroscopic evidence for a red, possibly water-ice-bearing object. Imaging confirms a diffuse coma present from our earliest observations, though no strong polarimetric features are spatially resolved. These findings may demonstrate that 3I represents a distinct type of comet, expanding the diversity of known interstellar bodies.

Keywords: Polarimetry, Interstellar objects
Protostars at Subsolar Metallicity: First Detection of Large Solid-state Complex Organic Molecules in the Large Magellanic Cloud. We present the results of James Webb Space Telescope observations of the protostar ST6 in the Large Magellanic Cloud (LMC) with the Medium Resolution Spectrograph of the Mid-Infrared Instrument (4.9─27.9 μm). Characterized by one-third to half-solar metallicity and strong UV radiation fields, the environment of the LMC allows us to study the physics and chemistry of star-forming regions under conditions similar to those at earlier cosmological epochs. We detected five icy complex organic molecules (COMs): methanol (CH3OH), acetaldehyde (CH3CHO), ethanol (CH3CH2OH), methyl formate (HCOOCH3), and acetic acid (CH3COOH). This is the first conclusive detection of CH3COOH ice in an astrophysical context, and CH3CHO, CH3CH2OH, and HCOOCH3 ices are the first secure detections outside the Galaxy and in a low-metallicity environment. We address the presence of glycolaldehyde (HOCH2CHO, a precursor of biomolecules), an isomer of HCOOCH3 and CH3COOH, but its detection is inconclusive. ST6's spectrum is also rich in simple ices: H2O, CO2, CH4, SO2, H2CO, HCOOH, OCN−, HCOO−, NH3, and NH4+. We obtain the composition and molecular abundances in the icy dust mantles by fitting the spectrum in the 6.8─8.4 μm range with a large sample of laboratory ice spectra using the ENIIGMA fitting tool or the local continuum method. We found differences in the simple and COM ice abundances with respect to H2O ice between ST6 and Galactic protostars that likely reflect differences in metallicity and UV flux. More laboratory ice spectra of COMs are needed to better reconstruct the observed infrared spectra of protostars.

Keywords: Ice composition, Infrared spectroscopy, Chemical abundances, Astrochemistry, Star formation, Protostars, Magellanic Clouds
First Results from ALPPS: A Sub-Alfvénic Streamer in SVS 13A. We present the first results from the Atacama Large Millimeter/submillimeter Array Perseus Polarization Survey, focusing on the magnetic field in the SVS 13A circumbinary disk. The data set includes full Stokes dust continuum observations at  ∼0.″3  and 870 μm, as well as molecular line emission from C17O(J = 3 → 2) at  ∼0.″3 , C18O(J = 2 → 1) at  ∼0.″2 , and DCN(J = 3 → 2) at  ∼0.″1  angular resolution. Our observations resolve both a previously identified dust spiral and an infalling streamer, capturing their spatial and kinematic structures. The streamer is traced from scales &gt;300 au down to the circumbinary disk. Using alignment measure (AM) maps and histograms that compare the orientations of the plane-of-sky magnetic field with local intensity and velocity gradients, we find that the AM distribution peaks at a value of 1. This AM peak strongly suggests alignment between the field and the dust total intensity emission, as well as between the field and the gas velocity, which in turn suggests grain alignment by magnetic fields. From our data, we derive a magnetic field strength, Bpos ∼ 1.1 ± 0.6 mG, and a kinetic-to-magnetic energy ratio of 0.5 ± 0.4, suggesting magnetic dominance. We also produced a map of the Alfvénic Mach number, finding  MA&lt;1  along the streamer, consistent with sub-Alfvénic infalling motions. Therefore, the field is likely facilitating the inflow of material from the envelope onto the disk by constraining movement across the field lines. This represents the first detection of a magnetically sub-Alfvénic infalling streamer in a protostellar system.

Keywords: Star formation
Trans-Neptunian Object Colors as Evidence for a Past Close Stellar Flyby to the Solar System. Thousands of small bodies, known as trans-Neptunian objects (TNOs), orbit the Sun beyond Neptune. TNOs are remnants of the planets' formation from a disk of gas and dust, so it is puzzling that they move mostly on eccentric orbits inclined to the planetary plane and show a complex red-to-gray color distribution. A close stellar flyby can account for the TNOs' dynamics, but it is unclear if this can also explain the correlation between their colors and orbital characteristics. Assuming an initial red-to-gray color gradient in the disk, our numerical study finds that the spiral arms induced by the stellar flyby simultaneously lead to the observed TNOs' color patterns and orbital dynamics. The combined explanation of these TNO properties strengthens the evidence for a close flyby of another star to the young solar system. Our study predicts that (1) small TNOs beyond 60 au will mostly be gray, and (2) retrograde TNOs will lack the color most common to high-inclination TNOs. The anticipated TNO discoveries by the Vera Rubin telescope will be able to test these predictions. A confirmed flyby would allow us to reveal the chemical composition of the solar system's primordial disk.

Keywords: Trans-Neptunian objects
Separating Photospheric and Starspot Magnetic Fields in Pre-main-sequence Stars Using IGRINS Spectroscopy. Magnetic fields in pre-main-sequence (PMS) stars regulate angular momentum evolution, drive magnetic activity, and modify stellar structure, yet their surface distributions remain poorly constrained. Traditional single-component Zeeman broadening analyses typically yield mean field strengths of 2─4 kG, sometimes exceeding the photospheric equipartition limit, and assume complete magnetic coverage. These assumptions conflict with evidence that strong fields are concentrated in cool starspots. Here, we present the first systematic separation of photospheric and starspot magnetic field strengths in PMS stars, using high-resolution (R ≍ 45,000) H- and K-band spectra from the Raw and Reduced IGRINS Archive. By modeling temperature and magnetic field strength simultaneously for a vetted sample of 33 classes II─III young stellar objects, we find median photospheric field strengths of 1.2 kG and median spot field strengths over 2 times stronger at 2.56 kG, resolving the apparent superequipartition tension and removing the need for a unity magnetic filling factor. Our results show that PMS surfaces are permeated by concentrated, kilogauss-strength spot fields covering 27%─83% of the visible hemisphere. This two-component framework offers a physically motivated means to reconcile spectroscopic and imaging-based magnetic diagnostics and enables large-scale magnetic population studies across young clusters and star-forming regions.

Keywords: Early stellar evolution, Starspots, Pre-main sequence stars, Magnetic fields
The Perfect Host: JWST Cepheid Observations in a Background-free Type Ia Supernova Host Confirm No Bias in Hubble-constant Measurements. Cycle 1 JWST observations of Cepheids in Type Ia supernova (SN Ia) hosts resolved their red-giant-dominated near-infrared backgrounds, sharply reducing crowding and showing that photometric bias in lower-resolution Hubble Space Telescope (HST) data does not account for the Hubble tension. We present cycle 2 JWST observations of &gt;100 Cepheids in NGC 3447, a unique system that pushes this test to the limit by transitioning from low to no background contamination. NGC 3447, an SN Ia host at D ≍ 25 Mpc, is an interacting pair comprising (i) a spiral with mixed stellar populations, typical of H0 calibrators, and (ii) a young, star-forming companion (NGC 3447A) devoid of old stars and hence stellar crowding—a rare "perfect host" for testing photometric bias. We detect ∼60 long-period Cepheids in each, enabling a "three-way comparison" across HST, JWST, and background-free conditions. We find no component-to-component offset (σ &lt; 0.03 mag; a calibration-independent test) and a 50% reduction in scatter to ∼0.12 mag in the background-free case, the tightest seen for any SN Ia host. Across cycles 1─2, we also measure Cepheids in all SH0ES hosts observed by JWST (19 hosts of 24 SNe Ia; &gt;50% of the sample) and find no evidence of bias relative to HST photometry, including for the most crowded, distant hosts. These observations constitute the most rigorous test yet of Cepheid distances and provide strong evidence for their reliability. Combining JWST Cepheid measurements in 19 hosts (24 SNe Ia) with HST data (37 hosts, 42 SNe Ia) yields H0 = 73.49 ± 0.93 km s−1 Mpc−1. Including 35 TRGB-based calibrations (from HST and JWST) totals 55 SNe Ia and gives H0 = 73.18 ± 0.88 km s−1 Mpc−1─∼6σ above the ΛCDM+cosmic microwave background expectation.

Keywords: Hubble constant, James Webb Space Telescope, Cepheid distance
A Hyperactive Fast Radio Burst Pinpointed in an SMC-like Satellite Host Galaxy. Precise localizations of fast radio bursts (FRBs) are essential for uncovering their host galaxies and immediate environments. We present the milliarcsecond-precision European VLBI Network localization of FRB 20240114A, a hyperactive repeating FRB, achieving ≲90 × 30 mas (1σ) accuracy. This precision places the burst 0.5 kpc from the nucleus of its low-metallicity star-forming dwarf host at a spectroscopic redshift of z = 0.130287. Our Gran Telescopio CANARIAS spectroscopic follow-up reveals that the dwarf FRB host is gravitationally bound to a more massive, star-forming spiral galaxy. This establishes the first known instance of an FRB residing in a satellite galaxy within a larger galactic system. This configuration, analogous to the Small Magellanic Cloud orbiting the Milky Way (but at a lower overall mass scale), expands the known diversity of FRB host environments and offers important insights for interpreting seemingly "hostless" or highly offset FRBs. Furthermore, our detailed dispersion measure (DM) budget analysis indicates that the dominant contribution to FRB 20240114A's DM likely originates from the foreground galaxy halos. This finding addresses the anomalously high DM observed for this FRB and underscores the significant role of intervening foreground structures in shaping observed FRB DMs, which is important for accurate FRB-based cosmological measurements. Our results highlight the importance of deep, high-resolution optical/infrared observations (e.g., with the Hubble or James Webb Space Telescopes) to fully leverage our precise radio localization and probe the immediate astrophysical birthplaces of FRB progenitors within these complex galactic systems.

Keywords: Very long baseline interferometry, Companion galaxies, Dwarf galaxies, Radio bursts, Radio transient sources
Cumulative Proton Right-handed Instabilities in the Young Solar Wind Observed by PSP. We present a detailed linear analysis of right-handed (RH) proton instabilities in beaming bi-Maxwellian/bi-Kappa plasma representative of young solar wind conditions currently explored by the Parker Solar Probe. At lower heliocentric distances, ion (proton) beams are more dense, and the associated wave fluctuations are predominantly RH polarized, strongly suggesting the presence of proton-beam plasma instabilities to explain not only the enhanced fluctuations but also the subsequent particle diffusion in energy and pitch angle. The study systematically investigates the cumulative effects of beam drift velocity and temperature anisotropies on the ion─ion resonant and proton firehose instabilities. By examining the variations in maximum growth rates, resonant factors, and instability thresholds across a broad range of plasma parameters, including beam and core anisotropies, density ratios, plasma beta, and suprathermal populations, this work identifies the key regimes where instabilities are enhanced or suppressed. The influence of suprathermal ions and electrons, modeled using Kappa distributions, is shown to significantly extend the unstable parameter space. Electron temperature anisotropy is also found to strongly modify the growth rates of these instabilities by changing their resonance conditions with beaming particles. This parametric study provides comprehensive guidance for future quasilinear or simulation studies by identifying the most physically relevant and numerically effective regimes for these instabilities in the solar wind and space plasmas.

Keywords: Space plasmas, Solar wind
AEOS: The Impact of Population III Initial Mass Function and Star-by-star Models in Galaxy Simulations. We explore the effect of variations in the Population III initial mass function (IMF) and star-by-star feedback on early galaxy formation and evolution using the AEOS simulations. We compare simulations with two different Population III IMFs: Mchar = 10 M⊙ and  Mmax=100M⊙  (Aeos10) and Mchar = 20 M⊙ and  Mmax=300M⊙  (Aeos20). Aeos20 produces significantly more ionizing photons, ionizing 30% of the simulation volume by z ≍ 14, compared to 9% in Aeos10. This enhanced ionization suppresses galaxy formation on the smallest scales. Differences in Population III IMF also affect chemical enrichment. Aeos20 produces Population II stars with higher abundances, relative to iron, of light and α-elements, a stronger odd─even effect, and a higher frequency of carbon-enhanced metal-poor stars. The abundance scatter between different Population II galaxies dominates the differences due to Population III IMF, though, implying a need for a larger sample of Population II stars to interpret the impact of Population III IMF on early chemical evolution. We also compare the AEOS simulations to traditional simulations that use single stellar population particles. We find that star-by-star modeling produces a steeper mass─metallicity relation due to less bursty feedback. These results highlight the strong influence of the Population III IMF on early galaxy formation and chemical evolution, emphasizing the need to account for IMF uncertainties in simulations and the importance of metal-poor Population II stellar chemical abundances when studying the first stars.

Keywords: Chemical enrichment, Dwarf galaxies, Population III stars, Ionization
Seismic Oscillations Excited by Giant Impacts in Directly Imaged Giant Planets. The radii and masses of many giant exoplanets imply their interiors each contain more than ∼100 M⊕ of solids. A large metal content may arise when a giant planet grows by colliding and merging with multiple ∼10 M⊕ solid cores. Here we show that a giant impact with a young gas giant excites long-lived seismic oscillations that can be detected photometrically. The mode lifetimes are close to the planet's Kelvin─Helmholtz time, a significant fraction of a young planet's age. The oscillation periods lie between tens of minutes to an hour, and the variability amplitudes can exceed a percent for several million years. Beta Pictoris b is a young super-Jupiter known to be highly metal-enriched. If a Neptune-mass (17 M⊕) body impacted β Pictoris b in the past ∼9─18 Myr, the planet could still be ringing with a percent-level photometric variability measurable with JWST.

Keywords: Radial pulsations, Non-radial pulsations, Direct imaging, Exoplanet formation, Extrasolar gaseous giant planets