Sazuna/UAT_keywords huggingface dataset:
Observations of the Crab Nebula and Pulsar with the Large-sized Telescope Prototype of the Cherenkov Telescope Array. The Cherenkov Telescope Array (CTA) is a next-generation ground-based observatory for gamma-ray astronomy at very high energies. The Large-Sized Telescope prototype (LST-1) is located at the CTA-North site, on the Canary Island of La Palma. LSTs are designed to provide optimal performance in the lowest part of the energy range covered by CTA, down to ≃20 GeV. LST-1 started performing astronomical observations in 2019 November, during its commissioning phase, and it has been taking data ever since. We present the first LST-1 observations of the Crab Nebula, the standard candle of very-high-energy gamma-ray astronomy, and use them, together with simulations, to assess the performance of the telescope. LST-1 has reached the expected performance during its commissioning period-only a minor adjustment of the preexisting simulations was needed to match the telescope's behavior. The energy threshold at trigger level is around 20 GeV, rising to ≃30 GeV after data analysis. Performance parameters depend strongly on energy, and on the strength of the gamma-ray selection cuts in the analysis: angular resolution ranges from 0.°12-0.°40, and energy resolution from 15%-50%. Flux sensitivity is around 1.1% of the Crab Nebula flux above 250 GeV for a 50 hr observation (12% for 30 minutes). The spectral energy distribution (in the 0.03-30 TeV range) and the light curve obtained for the Crab Nebula agree with previous measurements, considering statistical and systematic uncertainties. A clear periodic signal is also detected from the pulsar at the center of the Nebula.

Keywords: Gamma-ray sources, Astronomy data analysis, Pulsars, Pulsar wind nebulae, Gamma-ray astronomy
Negative Lags on the Viscous Timescale in Quasar Photometry and Prospects for Detecting More with LSST. The variability of quasar light curves can be used to study the structure of quasar accretion disks. For example, continuum reverberation mapping uses delays between variability in short and long wavelength bands (short lags) to measure the radial extent and temperature profile of the disk. Recently, a potential reverse lag, where variations in shorter wavelength bands lag the longer wavelength bands at the much longer viscous timescale, was detected for Fairall 9. Inspired by this detection, we derive a timescale for these long negative lags from fluctuation propagation models and recent simulations. We use this timescale to forecast our ability to detect long lags using the Vera Rubin Legacy Survey of Space and Time (LSST). After exploring several methods, including the interpolated cross-correlation function, a Von-Neumann estimator, JAVELIN, and a maximum-likelihood Fourier method, we find that our two main methods, JAVELIN and the maximum-likelihood method, can together detect long lags of up to several hundred days in mock LSST light curves. Our methods work best on proposed LSST cadences with long season lengths, but can also work for the current baseline LSST cadence, especially if we add observations from other optical telescopes during seasonal gaps. We find that LSST has the potential to detect dozens to hundreds of additional long lags. Detecting these long lags can teach us about the vertical structure of quasar disks and how it scales with different quasar properties.

Keywords: Accretion, Black holes, High energy astrophysics, Quasars, Reverberation mapping, Disk flaring, Active galactic nuclei
Disk and Envelope Streamers of the GGD 27-MM1 Massive Protostar. We present new Atacama Large Millimeter/submillimeter Array 0.98 mm observations of the continuum emission and several molecular lines toward the high-mass protostellar system GGD 27-MM1, driving the HH 80-81 radio jet. The detailed analysis of the continuum and the CH3CN molecular emission allows us to separate the contributions from the dust content of the disk (extending up to 190 au), the molecular content of the disk (extending from 140-360 au), and the content of the envelope, revealing the presence of several possible accretion streamers (also seen in other molecular tracers, such as CH3OH). We analyze the physical properties of the system, producing temperature and column density maps, and radial profiles for the disk and the envelope. We qualitatively reproduce the trajectories and line-of-sight velocities of the possible streamers using a theoretical model approach. An ad hoc model of a flared disk comprising a hot dust disk embedded in cold gas fits the H2S emission, which revealed the molecular disk as a crescent shape with a prominent central absorption. Another fit to the central absorption spectrum suggests that the absorption is probably caused by different external cold layers from the envelope or the accretion streamers. Finally, the analysis of the rotation pattern of the different molecular transitions in the molecular disk suggests that there is an inner zone devoid of molecular content.

Keywords: Interstellar molecules, Protostars, Young stellar objects, Interstellar medium
Quantifying Poynting Flux in the Quiet Sun Photosphere. Poynting flux is the flux of magnetic energy, which is responsible for chromospheric and coronal heating in the solar atmosphere. It is defined as a cross product of the electric and magnetic fields, and in ideal MHD conditions it can be expressed in terms of the magnetic field and plasma velocity. Poynting flux has been computed for active regions and plages, but estimating it in the quiet Sun (QS) remains challenging due to resolution effects and polarimetric noise. However, with the upcoming DKIST capabilities, such estimations will become more feasible than ever before. Here, we study QS Poynting flux in SUNRISE/IMaX observations and MURaM simulations. We explore two methods for inferring transverse velocities from observations-FLCT and a neural network-based method DeepVel-and show DeepVel to be the more suitable method in the context of small-scale QS flows. We investigate the effect of azimuthal ambiguity on Poynting flux estimates, and we describe a new method for azimuth disambiguation. Finally, we use two methods for obtaining the electric field. The first method relies on an idealized Ohm's law, whereas the second is a state-of-the-art inductive electric field inversion method PDFI_SS. We compare the resulting Poynting flux values with theoretical estimates for chromospheric and coronal energy losses and find that some of the Poynting flux estimates are sufficient to match the losses. Using MURaM simulations, we show that photospheric Poynting fluxes vary significantly with optical depth, and that there is an observational bias that results in underestimated Poynting fluxes due to an unaccounted shear term contribution.

Keywords: Solar atmosphere, Solar photosphere, The Sun, Solar physics, Solar chromospheric heating
Cross Correlation of Pencil-beam Galaxy Surveys and Line-intensity Maps: An Application of the James Webb Space Telescope. Line-intensity mapping (IM) experiments seek to perform statistical measurements of large-scale structure with spectral lines such as 21 cm, CO, and Lyα. A challenge in these observations is to ensure that astrophysical foregrounds, such as galactic synchrotron emission in 21 cm measurements, are properly removed. One method that has the potential to reduce foreground contamination is to cross correlate with a galaxy survey that overlaps with the IM volume. However, telescopes sensitive to high-redshift galaxies typically have small field of views compared to IM surveys. Thus, a galaxy survey for cross correlation would necessarily consist of pencil beams that sparsely fill the IM volume. In this paper, we develop the formalism to forecast the sensitivity of cross correlations between IM experiments and pencil-beam galaxy surveys. We find that a random distribution of pencil beams leads to very similar overall sensitivity as a lattice spaced across the IM survey and derive a simple formula for random configurations that agrees with the Fisher matrix formalism. We explore examples of combining high-redshift James Webb Space Telescope (JWST) observations with both an SPHEREx-like Lyα IM survey and a 21 cm experiment based on the Hydrogen Epoch of Reionization Array (HERA). We find that the JWST-SPHEREx case is promising, leading to a total signal-to-noise ratio of ~5 after 100 total hours of JWST (at z = 7). We find that HERA is not well-suited for this approach owing to its drift-scan strategy, but that a similar experiment that can integrate down on one field could be.

Keywords: Cosmology, Reionization, High-redshift galaxies
High-resolution Observations of the Low Atmospheric Response to Small Coronal Heating Events in an Active Region Core. High-resolution spectral observations of the lower solar atmosphere (chromosphere and transition region) during coronal heating events, in combination with predictions from models of impulsively heated loops, provide powerful diagnostics of the properties of the heating in active region cores. Here, we analyze the first coordinated observations of such events with the Interface Region Imaging Spectrograph (IRIS) and the CHROMospheric Imaging Spectrometer (CHROMIS), at the Swedish 1 m Solar Telescope (SST), which provided extremely high spatial resolution and revealed chromospheric brightenings with spatial dimensions down to ~150 km. We use machine-learning methods (k-means clustering) and find significant coherence in the spatial and temporal properties of the chromospheric spectra, suggesting, in turn, coherence in the spatial and temporal distribution of the coronal heating. The comparison of IRIS and CHROMIS spectra with simulations suggests that both nonthermal electrons with low energy (low-energy cutoff ~5 keV) and direct heating in the corona transported by thermal conduction contribute to the heating of the low atmosphere. This is consistent with growing evidence that nonthermal electrons are not uncommon in small heating events (nanoflare to microflares), and that their properties can be constrained by chromospheric and transition region spectral observations.

Keywords: Solar atmosphere, Solar ultraviolet emission, Solar extreme ultraviolet emission, Solar chromospheric heating, Solar coronal loops, Solar coronal heating, Active sun, Solar physics, Solar active regions, Solar transition region, Active solar corona, Solar chromosphere
The Hubble Space Telescope Survey of M31 Satellite Galaxies. II. The Star Formation Histories of Ultrafaint Dwarf Galaxies. We present the lifetime star formation histories (SFHs) for six ultrafaint dwarf (UFD; M  V  &gt; - 7.0, $4.9\lt {\mathrm{log}}_{10}({M}_{* }(z=0)/{M}_{\odot })\lt 5.5$ ) satellite galaxies of M31 based on deep color-magnitude diagrams constructed from Hubble Space Telescope imaging. These are the first SFHs obtained from the oldest main-sequence turnoff of UFDs outside the halo of the Milky Way (MW). We find that five UFDs formed at least 50% of their stellar mass by z = 5 (12.6 Gyr ago), similar to known UFDs around the MW, but that 10%-40% of their stellar mass formed at later times. We uncover one remarkable UFD, And XIII, which formed only 10% of its stellar mass by z = 5, and 75% in a rapid burst at z ~ 2-3, a result that is robust to choices of underlying stellar model and is consistent with its predominantly red horizontal branch. This "young" UFD is the first of its kind and indicates that not all UFDs are necessarily quenched by reionization, which is consistent with predictions from several cosmological simulations of faint dwarf galaxies. SFHs of the combined MW and M31 samples suggest reionization did not homogeneously quench UFDs. We find that the least-massive MW UFDs (M *(z = 5) ≲ 5 × 104 M ⊙) are likely quenched by reionization, whereas more-massive M31 UFDs (M *(z = 5) ≳ 105 M ⊙) may only have their star formation suppressed by reionization and quench at a later time. We discuss these findings in the context of the evolution and quenching of UFDs.

Keywords: Dwarf galaxies, Galaxy quenching, Hertzsprung Russell diagram, Reionization, Andromeda Galaxy
The High-redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey: Investigating the Role of Environment on Bent Radio AGNs Using LOFAR. Bent radio active galactic nucleus (AGN) morphology depends on the density of the surrounding gas. However, bent sources are found inside and outside clusters, raising the question of how environment impacts bent AGN morphology. We analyze new LOw-Frequency Array the LOFAR Two-metre Sky Survey (LoTSS) Data Release II observations of 20 bent AGNs in clusters and 15 not in clusters from the high-z Clusters Occupied by Bent Radio AGN (COBRA) survey (0.35 &lt; z &lt; 2.35). We measure the impact of environment on size, lobe symmetry, and radio luminosity. We find that the most asymmetric radio lobes lie outside of clusters, and we uncover a tentative anticorrelation between the total projected physical area and cluster overdensity. Additionally, we, for the first time, present spectral index measurements of a large sample of high-z bent sources using LoTSS and Very Large Array Faint Images of the Radio Sky at Twenty-centimeters (VLA FIRST) observations. We find that the median spectral index for the cluster sample is -0.76 ± 0.01, while the median spectral index for the noncluster sample is -0.81 ± 0.02. Furthermore, 13 of 20 cluster bent AGNs have flat cores (α ≥ -0.6) compared to 4 of 15 of noncluster bent AGNs, indicating a key environmental signature. Beyond core spectral index, bent AGNs inside and outside clusters are remarkably similar. We conclude that the noncluster sample may be more representative of bent AGNs at large offsets from the cluster center (&gt; 1.2 Mpc) or bent AGNs in weaker groups rather than the field.

Keywords: Radio active galactic nuclei, High-redshift galaxy clusters
Connection between Polytropic Index and Heating. The paper derives the one-to-one connecting relationships between plasma heating and its polytropic index, and addresses the consequences through the transport equation of temperature. Thermodynamic polytropic processes are classified in accordance to their polytropic index, the exponent of the power-law relationship of thermal pressure expressed with respect to density. These processes generalize the adiabatic one, where no heating is exchanged between the system and its environment. We show that, in addition to heating terms, the transport equation of temperature depends on the adiabatic index, instead of a general, nonadiabatic polytropic index, even when the plasma follows nonadiabatic processes. This is because all the information regarding the system's polytropic index is contained in the heating term, even for a nonconstant polytropic index. Moreover, the paper (i) defines the role of the polytropic index in the context of heating; (ii) clarifies the role of the nonadiabatic polytropic index in the transport equation of temperature; (iii) provides an alternative method for deriving the turbulent heating through the comparably simpler polytropic index path; and, finally, (iv) shows a one-component plasma proof-of-concept of this method and discusses the implications of such derived connecting relationships in the solar wind plasma in the heliosphere.

Keywords: Space plasmas, Polytropes, Heliosphere
Non-universality of the Turbulent Spectra at Sub-ion Scales in the Solar Wind: Dispersive Effects versus the Doppler Shift. Large surveys of the power spectral density of the magnetic fluctuations in the solar wind have reported different slope distributions at MHD, sub-ion and sub-electron scales: the smaller the scale, the broader the distribution. Here, we review briefly some of the most relevant explanations of the broadening of the slopes at sub-ion scales. Then, we present a new one that has been overlooked in the literature, which is based on the relative importance of the dispersive effects with respect to the Doppler shift due to the mean flow speed. We build a toy model based on a dispersion relation of a linear mode that matches at high frequency (ω ≳ ω ci) the Alfvén (respectively whistler) mode at high oblique (respectively quasi-parallel) propagation angles θ  kB . Starting with a double power-law spectrum of turbulence ${{k}_{\perp }}^{-1.66}$ in the inertial range and ${{k}_{\perp }}^{-2.8}$ at the sub-ion scales, the transformed spectrum (in frequency f) as it would be measured in the spacecraft reference frame shows a broad range of slopes at the sub-ion scales that depend both on the angle θ  kB  and the flow speed V. Varying θ  kB  in the range 4°-106° and V in the range 400-800 km s-1 the resulting distribution of slopes at the sub-ion scales reproduces quite well the observed one in the solar wind. Fluctuations in the solar wind speed and the wavevector anisotropy of the turbulence may explain (or at least contribute to) the variability of the spectral slopes reported from spacecraft observations in the solar wind.

Keywords: Interplanetary turbulence, Solar wind
Let's Sweep: The Effect of Evolving J <SUB>2</SUB> on the Resonant Structure of a Three-planet System. Short and ultrashort period planets are peculiar types of exoplanets with periods as short as a few days or less. Although it is challenging to detect them, already several have been observed, with many additional candidates. If these planets have formation pathways similar to their longer-period counterparts, they are predicted to reside in multiplanet systems. Thus, gravitational perturbation from potential planetary neighbors may affect their orbital configuration. However, due to their close proximity to their host star, they are also subject to general relativity precession and torques from the stellar spin quadrupole moment (J 2). Here we show that an evolving J 2 due to magnetic braking affects the magnitude and location of secular resonances of the short-period planet in a multiplanet system, thus driving the short-period planet into and out of a secular resonance, exciting the planet's eccentricity and inclination. The high inclination can hinder transit observation and, in some cases, the high eccentricity may result in an unstable configuration. We propose that evolving J 2 in a multiplanet system can be critical to understanding the detectability and stability of short-period planets.

Keywords: Exoplanet dynamics, Exoplanet evolution, Exoplanet formation, Planetary system formation
Unraveling the Complexity of Dwarf Galaxy Dynamics: A Study of Binary Orbital Motions. We investigate the impact of binary orbital motions on the dynamical modeling of dwarf galaxies with intrinsic line-of-sight velocity dispersions ( ${\sigma }_{{v}_{r}}$ ) of 1-9 km s-1. Using dwarf galaxies from the AURIGA level-2 and level-3 simulations, we apply the Jeans Anisotropic Multi-Gaussian Expansion modeling to tracer stars before and after including binaries to recover the dynamical masses. The recovered total masses within the half-mass radius of tracers, M(&lt; r half), are always inflated due to binary motions, with greater inflations occurring for smaller ${\sigma }_{{v}_{r}}$ . However, many dwarf galaxies experience central density deflated due to binary motions, with little dependence on ${\sigma }_{{v}_{r}}$ . This is due to the negative radial gradients in the velocity dispersion profiles, with the fractional inflation in ${\sigma }_{{v}_{r}}$ due to binaries more significant in outskirts. An extreme binary fraction of 70% can lead to central density deflation of up to 10%-20% at 3 km s-1 &lt; ${\sigma }_{{v}_{r}}$ &lt; 8 km s-1, with M( &lt; r half) inflated by 4% at 9 km s-1 and up to 15% at 3 km s-1. A lower binary fraction of 36% leads to similar deflations, with the inflations decreasing to approximately 10% at 3 km s-1 and becoming statistically insignificant. The choice of binary orbit distribution models does not result in significant differences, and observational errors tend to slightly weaken the deflations in the recovered central density. Two observations separated by 1 yr to exclude binaries lead to almost zero inflations/deflations for a binary fraction of 36% over 3 km s-1 &lt; ${\sigma }_{{v}_{r}}\lt 9$ km s-1. For ${\sigma }_{{v}_{r}}\sim 1$ km s-1 to 3 km s-1, a binary fraction of 70% (36%) still results in 60% (30%) to 10% (1%) of inflations in M( &lt; r half), even with two-epoch observation.

Keywords: Hydrodynamical simulations, Dwarf galaxies, Binary stars, Dark matter
The Cool Circumgalactic Medium of Low-redshift Star-forming Galaxies. I. Empirical Model and Mean Properties. We present an analytic model for the cool, T ~ 104 K, circumgalactic medium (CGM), describing the gas distribution, and thermal and ionization states. Our model assumes (total) pressure equilibrium with the ambient warm/hot CGM, photoionization by the metagalactic radiation, and allows for nonthermal pressure support, parameterized by the ratio of thermal pressures, η = P hot,th/P cool,th. We apply the model to the COS-Halos measurements and find that a nominal model with η = 3, gas distribution out to r ≈ 0.6R vir, and M cool = 3 × 109 M ⊙, corresponding to a volume filling fraction of f V,cool ≈ 1%, reproduces the H I and low/intermediate metal ions (C II, C III, Si II, Si III, and Mg II) mean column densities. Variation of ±0.5 dex in η or M cool encompasses ~2/3 of the scatter between objects. Our nominal model underproduces the measured C IV and Si IV columns, and these can be reproduced with (i) a cool phase with M cool ~ 1010 M ⊙ and η ≈ 5, or (ii) cooling or mixing gas at intermediate temperatures, with M ~ 1.5 × 1010 M ⊙ and occupying ~1/2 of the total CGM volume. For cool gas with f V,cool ≈ 1%, we estimate an upper limit on the cloud sizes, R cl ≲ 0.5 kpc. Our results suggest that for the average galaxy CGM, the mass and nonthermal support in the cool phase are lower than previously estimated, and extreme scenarios are not necessary. We estimate the rates of cool gas depletion and replenishment, and find accretion onto the galaxy can be offset, allowing ${\dot{M}}_{\mathrm{cool}}\approx 0$ over long timescales.

Keywords: Galaxy formation, Quasar absorption line spectroscopy, Galaxy structure, Circumgalactic medium, Galactic and extragalactic astronomy, Galaxy evolution, Interstellar medium, Intergalactic medium, Galaxy processes
Simultaneous 2.25/8.60 GHz Observations of the Magnetar XTE J1810-197. We did 194 epochs of simultaneous 2.25/8.60 GHz observations of XTE J1810-197 in 926 days shortly following its reactivation in 2018 with Shanghai Tian Ma Radio Telescope (TMRT). Although its integrated profiles changed with both time and frequency during this period, they could be classified into 12 types according to phase areas of active radiation components. After MJD 59015, XTE J1810-197 turned from the normal emission state into the spiky emission state that was manifesting as a series of bright narrow sub-pulse bursts at both 2.25 and 8.60 GHz. Due to its variable integrated profiles and unsteady rotations, we got the spin frequency ν and spin-frequency derivatives $\dot{\nu }$ with the piecewise fitting method. In addition, its long-term declining trend of ν was also obtained as $\dot{\nu }=-3.2(1)\times {10}^{-13}$ s-2 with the linear fitting method based on our observations spanning a comparatively longer period. We found its flux densities went through three stages: sharp decrease, stabilization, and day-to-day fluctuations in our dual-frequency observations. Although the flux density showed different stages, XTE J1810-197 showed a relatively flat spectrum (α &gt; -1) in most observations. Assuming an ideal dipole magnetic field as some previous research works, we obtained the emission heights of XTE J1810-197 were about 7.5(9) × 104 km and 2.38(7) × 104 km at 2.25 and 8.60 GHz, respectively. We also found that its emission heights would decrease rapidly with the degree of magnetic field twisting.

Keywords: Magnetars, Radio pulsars