Sazuna/UAT_keywords huggingface dataset:
Forecasts and Statistical Insights for Line Intensity Mapping Cross-correlations: A Case Study with 21 cm × [C II]. Intensity mapping—the large-scale mapping of selected spectral lines without resolving individual sources—is quickly emerging as an efficient way to conduct large cosmological surveys. Multiple surveys covering a variety of lines (such as the hydrogen 21 cm hyperfine line, carbon-monoxide rotational lines, and [C II] fine-structure lines, among others) are either observing or will soon be online, promising a panchromatic view of our Universe over a broad redshift range. With multiple lines potentially covering the same volume, cross-correlations have become an attractive prospect, both for probing the underlying astrophysics and for mitigating observational systematics. For example, cross-correlating 21 cm and [C II] intensity maps during reionization could reveal the characteristic scale of ionized bubbles around the first galaxies, while simultaneously providing a convenient way to reduce independent foreground contaminants between the two surveys. However, many of the desirable properties of cross-correlations in principle emerge only under ideal conditions, such as infinite ensemble averages. In this paper, we construct an end-to-end pipeline for analyzing intensity mapping cross-correlations, enabling instrumental effects, foreground residuals, and analysis choices to be propagated through Monte Carlo simulations to a set of rigorous error properties, including error covariances, window functions, and full probability distributions for power-spectrum estimates. We use this framework to critically examine the applicability of simplifying assumptions such as the independence and Gaussianity of power-spectrum errors. As worked examples, we forecast the sensitivity of near-term and futuristic 21 cm × [C II] cross-correlation measurements, providing recommendations for survey design.

Keywords: Interstellar line emission, Large-scale structure of the universe, H I line emission, CO line emission, Reionization, Radio astronomy
Damping of Strong GHz Waves near Magnetars and the Origin of Fast Radio Bursts. We investigate how a fast radio burst (FRB) emitted near a magnetar would propagate through its surrounding dipole magnetosphere at radii r = 107–109 cm. First, we show that a GHz burst emitted in the O-mode with luminosity L ≫ 1040 erg s‑1 is immediately damped for all propagation directions except a narrow cone along the magnetic axis. Then, we examine bursts in the X-mode. GHz waves propagating near the magnetic equator behave as magnetohydrodynamic (MHD) waves if they have L ≫ 1040 erg s‑1. The waves develop plasma shocks in each oscillation and dissipate at  r∼3×108L42‑1/4  cm. Waves with lower L or propagation directions closer to the magnetic axis do not obey MHD. Instead, they interact with individual particles and require a kinetic description. The kinetic interaction quickly accelerates particles to Lorentz factors 104–105 at the expense of the wave energy, which again results in strong damping of the wave. In either propagation regime, MHD or kinetic, the dipole magnetosphere surrounding the FRB source acts as a pillow absorbing the radio burst and reradiating the absorbed energy in X-rays. These results constrain the origin of observed FRBs. We argue that the observed FRBs avoid damping because they are emitted by relativistic outflows from magnetospheric explosions, so that the GHz waves do not need to propagate through the outer equilibrium magnetosphere surrounding the magnetar.

Keywords: Neutron stars, Plasma astrophysics, X-ray transient sources, Radio bursts, Radiative processes, Magnetars
Comparison between the Emission Torus and the Measured Toroidal Magnetic Field for the Crab and Vela Nebulae. Polarization measurements provide insight into the magnetic field, a critical aspect of the dynamics and emission properties around the compact object. In this paper, we present the polarized magnetic field of the Crab outer torus and the Vela arc utilizing Imaging X-ray Polarimetry Explorer observation data. The polarization angle (PA) measured for the Crab outer torus exhibits two monotonic evolutions along the azimuth angle, which are consistent with the normal line of the elliptical ring. There is a slight increase in PA along the azimuth angle for both the inner arc and the outer arc of the Vela Nebula. The polarized magnetic vector along the outer torus of the Crab Nebula shows the polarized magnetic field aligns with the Crab outer torus structure. The PA variation along the Crab outer torus suggests a bulk flow speed of 0.8c. Meanwhile, the Vela Nebula polarized magnetic field does not exactly align with the Vela arc structure. We noted that the Crab Nebula possesses a polarized toroidal magnetic field, whereas the Vela Nebula exhibits an incomplete toroidal magnetic field.

Keywords: Magnetic fields, Pulsar wind nebulae
Probing Blackbody Components in Gamma-Ray Bursts from Black Hole Neutrino-dominated Accretion Flows. A stellar-mass black hole (BH) surrounded by a neutrino-dominated accretion flow (NDAF) is generally considered to be the central engine of gamma-ray bursts (GRBs). Neutrinos escaping from the disk will annihilate outside the disk to produce the fireball that could power GRBs with blackbody (BB) components. The initial GRB jet power and fireball launch radius are related to the annihilation luminosity and annihilation height of the NDAFs, respectively. In this paper, we collect seven GRBs with known redshifts and identified BB components to test whether the NDAF model works. We find that, in most cases, the values of the accretion rates and the central BH properties are all in the reasonable range, suggesting that these BB components indeed originate from the neutrino annihilation process.

Keywords: Accretion, Gamma-ray bursts, Black holes
Fast Radio Bursts with Narrow Beaming Angles Can Escape from Magnetar Magnetospheres. Fast radio bursts (FRBs) are millisecond-duration transients observed in the radio band, with their origin and radiation mechanism remaining unclear to date. Growing evidence indicates that at least some FRBs originate from magnetars and are likely generated within the magnetospheres of these highly magnetized neutron stars. However, a recent study suggested that FRBs originating from magnetar magnetospheres would be scattered by magnetospheric electron–positron pair plasma, making it impossible for them to escape successfully. In this paper, we first demonstrate that the scattering effect can be greatly attenuated if the angle between the FRB propagation direction and the background magnetic field is ∼10‑2 rad or smaller. When the angle is around 10‑1 rad, the beaming effect of FRBs becomes significant in reducing scattering. Such FRBs have small transverse spatial sizes, which can help them instantly push the front plasma laterally out of the radiation region. This significantly mitigates the FRB-induced two-photon annihilation reaction, γ + γ → e ‑ + e +, which was previously regarded as a key factor hindering the propagation of FRBs. A critical radiation-cone half-opening angle between 10‑3 and 10‑2 rad is found for an FRB with isotropic luminosity L iso ∼ 1042 erg s‑1 and emitted at a radius r em ≲ 109 cm in the magnetosphere of a magnetar. Smaller beaming angles and larger emission radii can be more advantageous for the propagation of FRBs in magnetospheres. Our result supports the scenario that FRBs could originate from magnetar magnetospheres.

Keywords: Magnetars, Radio bursts, Radio transient sources
On the 3D Transport of Low-energy Galactic Cosmic-ray and Jovian Electrons in the Inner Heliosphere in the Presence of a Fisk-type Heliospheric Magnetic Field. Modeling the transport of low-energy (1‑10 MeV) cosmic-ray electrons can lead to valuable insights as to the behavior of the heliospheric magnetic field (HMF), due to the fact that the mean free path (MFP) of these particles parallel to the HMF is significantly larger than their perpendicular MFP, and that these particles experience little in the way of drift due to gradients/curvatures in the HMF and along the heliospheric current sheet. Jovian electrons are particularly suitable for such an endeavour, as they originate from a decentral source in the inner heliosphere. To this end, the transport of these electrons is studied using a 3D, ab initio particle transport code that incorporates theoretical expressions for electron diffusion coefficients, and utilizes as inputs for these transport coefficients turbulence quantities calculated using a two-component turbulence transport model. The effects of a novel Fisk-type field on the transport of these Jovian electrons are investigated and compared with the effects of a standard Parker field.

Keywords: Interplanetary turbulence, Heliosphere, Cosmic rays
Accelerating Giant-impact Simulations with Machine Learning. Constraining planet-formation models based on the observed exoplanet population requires generating large samples of synthetic planetary systems, which can be computationally prohibitive. A significant bottleneck is simulating the giant-impact phase, during which planetary embryos evolve gravitationally and combine to form planets, which may themselves experience later collisions. To accelerate giant-impact simulations, we present a machine learning (ML) approach to predicting collisional outcomes in multiplanet systems. Trained on more than 500,000 N-body simulations of three-planet systems, we develop an ML model that can accurately predict which two planets will experience a collision, along with the state of the postcollision planets, from a short integration of the system's initial conditions. Our model greatly improves on non-ML baselines that rely on metrics from dynamics theory, which struggle to accurately predict which pair of planets will experience a collision. By combining with a model for predicting long-term stability, we create an ML-based giant-impact emulator, which can predict the outcomes of giant-impact simulations with reasonable accuracy and a speedup of up to 4 orders of magnitude. We expect our model to enable analyses that would not otherwise be computationally feasible. As such, we release our training code, along with an easy-to-use user interface for our collision-outcome model and giant-impact emulator (https://github.com/dtamayo/spock).

Keywords: Extrasolar rocky planets, Planet formation, Planetary dynamics, Exoplanets
Bursty Star Formation in Dwarfs is Sensitive to Numerical Choices in Supernova Feedback Models. Simulations of galaxy formation are mostly unable to resolve the energy-conserving phase of individual supernova events, having to resort to subgrid models to distribute the energy and momentum resulting from stellar feedback. However, the properties of these simulated galaxies, including the morphology, stellar mass formed, and the burstiness of the star formation history, are highly sensitive to the numerical choices adopted in these subgrid models. Using the SMUGGLE stellar feedback model, we carry out idealized simulations of an M vir ∼ 1010 M ⊙ dwarf galaxy, a regime where most simulation codes predict significant burstiness in star formation, resulting in strong gas flows that lead to the formation of dark matter cores. We find that by varying only the directional distribution of momentum imparted from supernovae to the surrounding gas, while holding the total momentum per supernova constant, bursty star formation may be amplified or completely suppressed, and the total stellar mass formed can vary by as much as a factor of ∼3. In particular, when momentum is primarily directed perpendicular to the gas disk, less bursty and lower overall star formation rates result, yielding less gas turbulence, more disky morphologies, and a retention of cuspy dark matter density profiles. An improved understanding of the nonlinear coupling of stellar feedback into inhomogeneous gaseous media is thus needed to make robust predictions for stellar morphologies and dark matter core formation in dwarfs independent of uncertain numerical choices in the baryonic treatment.

Keywords: Starburst galaxies, Galaxy dark matter halos, Galaxy structure, Dwarf galaxies, Computational methods, Star formation, Galaxy evolution
An Intermediate-mass Black Hole Hidden behind Thick Obscuration. Recent models suggest approximately half of all accreting supermassive black holes (SMBHs; M BH ≳ 105 M ⊙) are expected to undergo intense growth phases behind Compton-thick (N H &gt; 1.5 × 1024 cm‑2) veils of obscuring gas. However, despite being a viable source for the seeding of SMBHs, there are currently no examples known of a Compton-thick accreting intermediate-mass black hole (IMBH; M BH ∼ 102–105 M ⊙). We present a detailed X-ray spectral analysis of IC 750—the only active galactic nuclei (AGN) to date with a precise megamaser-based intermediate mass &lt;105 M ⊙. We find the equivalent width of neutral 6.4 keV Fe Kα to be  1.9‑1.0+2.2  keV via phenomenological modeling of the coadded 177 ks Chandra spectrum. Such large equivalent widths are seldom produced by processes other than fluorescence from dense obscuration. We fit three physically motivated X-ray spectral models to infer a range of possible intrinsic 2–10 keV luminosity posteriors that encompass the systematic uncertainties associated with a choice of model. Despite a wide range of predicted intrinsic 2–10 keV luminosities between ∼ 1041 and 1043 erg s‑1, all three models agree that IC 750 has a Compton-thick line-of-sight column density to &gt;99% confidence. Compton-thick obscuration is well-documented to impinge substantial bias on the pursuit of SMBH AGN. Our results thus provide the first indication that Compton-thick obscuration should also be properly considered to uncover and understand the IMBH population in an unbiased manner.

Keywords: Intermediate-mass black holes, Active galaxies, X-ray active galactic nuclei
A Possible Explanation of W-type Phenomena in V694 Peg. Three sets of complete multicolor light curves of V694 Peg observed in 2013, 2015, and 2019 were presented and analyzed. Our photometric solutions show that this system was an A-type shallow contact binary in 2013 and 2015 while it converted to a W-type one in 2019. A large cool spot on the component of this binary could explain the conversion, implying the W-type phenomena may be caused by the magnetic activity of the components. We have collected available data on this binary and calculated 505 times of light minimum, which spans 17 yr. The orbital period investigation based on these timings shows there is a long-term period increase at a rate of dP/dt = 4.3(±0.3)×10‑9 day yr‑1 superposed on a periodic variation with a period of 11.81(±0.06) yr. The cyclic orbital variation may be the result of magnetic activity cycles or the existence of a third body. Until now, only eight transformed systems, including V694 Peg, have been reported. Compared with other converting contact systems between A-type and W-type, V694 Peg is recorded as the shortest-period one. All of these converting systems are late-type (later than F7) contact binaries with the O'Connell effect and show cyclic period variation, which indicates that magnetic activity may be the reason for the conversion between the two types of contact binaries. For investigating the nature of A-type and W-type phenomena, the discovery of more converting contact binaries is essential.

Keywords: Late-type stars, Close binary stars, Eclipsing binary stars, Contact binary stars, Stellar evolution
Parametric Instability of Alfvén Waves and Wave Packets in Periodic and Open Systems. The parametric decay instability of Alfvén waves has been widely studied, but few investigations have examined wave packets of finite size and the effect of different boundary conditions on the growth rate. In this paper, we perform a linear analysis of circular and arc-polarized wave trains and wave packets in periodic and open boundary systems in a low-β plasma. We find that both types of wave are 3–5 times more stable in open boundary conditions compared to periodic. Additionally, once the wave packet width ℓ becomes smaller than the system size L, the growth rate decreases nearly with a power law γ ∝ ℓ/L. This study demonstrates that the stability of a pump wave cannot be separated from the laboratory settings, and that the growth rate of daughter waves depends on the conditions downstream and upstream of the pump wave and on the fraction of volume it fills. Our results can explain simulations and experiments of localized Alfvén waves. They also suggest that Alfvénic fluctuations in the solar wind, including sharp impulses known as switchbacks, can be more stable than traditional theory suggests depending on wind conditions.

Keywords: Magnetohydrodynamics, Solar wind, Alfven waves
Tracking Outflow Using Line Locking (TOLL). I. The Case Study of Quasar J221531-174408. Investigating line-locked phenomena within quasars is crucial for understanding the dynamics of quasar outflows, the role of radiation pressure in astrophysical flows, and the star formation history and metallicity of the early Universe. We have initiated the Tracking Outflow by Line Locking project to study quasar outflow by studying line-locking signatures using high-resolution high-signal-to-noise-ratio quasar spectra. In this paper, we present a case study of the line-locking signatures from QSO J221531-174408. The spectrum was obtained using the Very Large Telescope's UV Visual Echelle Spectrograph. We first identify associated absorbers in the spectrum using C IV, N V, and Si IV doublets and measure their velocity shifts, covering fractions, and column densities through a line-profile-fitting technique. Then we compare the velocity separations between different absorbers, and detect nine pairs of line-locked C IV doublets, three pairs of line-locked N V doublets, and one pair of line-locked Si IV doublets. This is one of the four quasars known to possess line-locked signatures in C IV, Si IV, and N V at the same time. We also find three complex line-locked systems, where three to five absorbers are locked together through multi-ion doublets. Our study suggests that line locking is a common phenomenon in the quasar outflows, and theoretical models involving more than two clouds and one ionic doublet are needed in the future to explain the formation of these complex line-locking signatures.

Keywords: Quasar absorption line spectroscopy
Estimating Dust Attenuation from Galactic Spectra. III. Radial Variations of Dust Attenuation Scaling Relations in MaNGA Galaxies. We investigate the radial dependence of the scaling relations of dust attenuation in nearby galaxies using integral field spectroscopy data from MaNGA. We identify ionized gas regions of kiloparsec size from MaNGA galaxies, and for each region we estimate both the stellar attenuation E(B ‑ V)star and gas attenuation E(B ‑ V)gas. We then quantify the correlations of 15 regional/global properties with E(B ‑ V)gas and E(B ‑ V)star, using both the feature importance obtained with the Random Forest regression technique and the Spearman correlation coefficients. The importance of stellar mass, metallicity, and nebular velocity dispersion found previously from studies based on the Sloan Digital Sky Survey can be reproduced if our analysis is limited to the central region of galaxies. The scaling relations of both E(B ‑ V)gas and E(B ‑ V)star are found to vary strongly as one goes from the galactic center to outer regions, and from Hα-bright regions to Hα-faint regions. For E(B ‑ V)gas, [N II]/[S II] is top-ranked with a much higher correlation coefficient than any other property at 0 &lt; R ≲ R  e , while [O III]/[O II] outperforms [N II]/[S II] as the leading property in the outermost region. For E(B ‑ V)star, stellar age shows the strongest correlation with no/weak dependence on radial distance, although ΣHα  and specific star formation rate present similarly strong correlations with E(B ‑ V)star in the galactic center. We find Hα-bright regions to generally show stronger correlations with E(B ‑ V)gas, while Hα-faint regions are more strongly correlated with E(B ‑ V)star, although this depends on individual properties and radial distance. The implications of our results for studies of high-z galaxies are discussed.

Keywords: Interstellar dust, Random Forests, Interstellar dust extinction, Scaling relations
JWST Imaging of Edge-on Protoplanetary Disks. III. Drastic Morphological Transformation Across the Mid-infrared in Oph163131. We present JWST broadband images of the highly inclined protoplanetary disk SSTc2d J163131.2-242627 (Oph163131) from 2.0 to 21 μm. The images show a remarkable evolution in disk structure with wavelength, quite different from previous JWST observations of other edge-on disks. At 2.0 and 4.4 μm, Oph163131 shows two scattering surfaces separated by a dark lane, typical of highly inclined disks. Starting at 7.7 μm, however, (1) the two linear nebulosities flanking the dark lane disappear; (2) the brighter nebula tracing the disk upper surface transitions into a compact central source distinctly larger than the JWST point-spread function and whose intrinsic size increases with wavelength; and (3) patches of extended emission appear at low latitudes, and at surprisingly large radii nearly twice that of the scattered light seen with Hubble Space Telescope and NIRCam, and of the gas. We interpret the compact central source as thermal emission from the star and the inner disk that is not seen directly, but which instead is able to progressively propagate to greater distances at longer wavelengths. The lack of sharp-edged structures in the extended patchy emission argues against the presence of shocks and suggests photoexcitation or stochastic heating of material smoothly flowing away from the star along the disk surface. Finally, the dark lane thickness decreases significantly between 0.6 and 4.4 μm, which indicates that the surface layers of Oph163131 lack grains larger than 1 μm.

Keywords: Dust continuum emission, Radiative transfer, Protoplanetary disks, Planet formation
On the Formation Height of Low-corona and Chromospheric Channels of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). The multiwavelength data from the Solar Dynamics Observatory is extensively used in studying the physics of the Sun and its atmosphere. In this study, we estimate the formation heights of low-corona and chromospheric channels of the Atmospheric Imaging Assembly (AIA) over the atmospheres of sunspot umbrae during the quiet condition period within 20 different active regions. The upward propagating slow magnetoacoustic waves of a 3 minute period, which are perpetually present in sunspots, are utilized for this purpose. Employing a cross-correlation technique, the most frequent time lag between different channel pairs is measured. By combining this information with the local sound speed obtained from the characteristic formation temperatures of individual channels, we estimate the respective formation heights. The median values of formation heights obtained across all active regions in our sample are 356, 368, 858, 1180, and 1470 km, respectively, for the AIA 1600, 1700, 304, 131, and 171 Å channels. The corresponding ranges in the formation heights are 247–453, 260–468, 575–1155, 709–1937, and 909–2585 km, respectively. These values are measured with respect to the Helioseismic Magnetic Imager continuum. We find the formation height of UV channels is quite stable (between 250 and 500 km) and displays only a marginal difference between the AIA 1600 and 1700 Å channels during quiet conditions. On the other hand, the formation height of coronal channels is quite variable.

Keywords: Magnetohydrodynamics, Sunspots