Sazuna/UAT_keywords huggingface dataset:
Experimental Determination of the Unusual CH Stretch Frequency of Protonated Fullerenes. We report experimental values for the CH stretch frequencies of the protonated fullerenes C60H+ and C70H+. Anharmonic frequency calculations at the B3LYP/6-31G level of theory, which are independent of empirical scaling factors, reproduce the experimental values to within approximately 5 cm‑1. Scaling theoretical harmonic frequencies by applying factors derived for polycyclic aromatic hydrocarbons deviate significantly from the experimentally measured frequency. We attribute this deviation to the unusual hydrocarbon structure that affects the degree of anharmonicity of the CH stretch. This result allows us to propose an original, specific scaling factor of 0.9524 to correct harmonic frequencies of CH stretches of protonated fullerenes calculated at the B3LYP/6-311 + G(d,p) level of theory. The special spectral position of the protonated fullerene CH stretch bands makes it a diagnostic marker that may aid in their detection in the interstellar medium.

Keywords: Polycyclic aromatic hydrocarbons, Infrared spectroscopy, Fullerenes, Laboratory astrophysics, Astrochemistry
Environmental Effects on the Stellar Mass Function in a z ∼ 3.3 Overdensity of Galaxies in the COSMOS Field. We present an analysis of the number density of galaxies as a function of stellar mass (i.e., the stellar mass function (SMF)) in the COSMOS field at z ∼ 3.3, making a comparison between the SMF in overdense environments and the SMF in the coeval field. In particular, this region contains the Elentári proto-supercluster, a system of six extended overdensities spanning ∼70 cMpc on a side. A clear difference is seen in the high-mass slope of these SMFs, with overdense regions showing an increase in the ratio of high-mass galaxies to low-mass galaxies relative to the field, indicating a more rapid buildup of stellar mass in overdense environments. This result qualitatively agrees with analyses of clusters at z ∼ 1, though the differences between protocluster and field SMFs at z ∼ 3.3 are smaller. While this is consistent with overdensities enhancing the evolution of their member galaxies, potentially through increased merger rates, whether this enhancement begins in protocluster environments or even earlier in group environments is still unclear. Though the measured fractions of quiescent galaxies between the field and overdense environments do not vary significantly, implying that this stellar mass enhancement is ongoing and any starbursts triggered by merger activity have not yet quenched, we note that spectroscopic observations are biased toward star-forming populations, particularly for low-mass galaxies. If mergers are indeed responsible, high-resolution imaging of Elentári and similar structures at these early epochs should then reveal increased merger rates relative to the field. Larger samples of well-characterized overdensities are necessary to draw broader conclusions in these areas. *Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 nonprofit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: Galaxy evolution, High-redshift galaxy clusters
Stellar Mergers or Truly Young? Intermediate-age Stars on Highly Radial Orbits in the Milky Way's Stellar Halo. Reconstructing the mass assembly history of the Milky Way relies on obtaining detailed measurements of the properties of many stars in the galaxy, especially in the stellar halo. One of the most constraining quantities is stellar age, as it can shed light on the accretion time and quenching of star formation in merging satellites. However, obtaining reliable age estimates for large samples of halo stars is difficult. We report published ages of 120 subgiant halo stars with highly radial orbits that likely belong to the debris of the Gaia-Enceladus/Sausage (GES) galaxy. The majority of these halo stars are old, with an age distribution characterized by a median of 11.6 Gyr and a 16th (84th) percentile of 10.5 (12.7) Gyr. However, the distribution is skewed, with a tail of younger stars that span ages down to ∼6–9 Gyr. All highly radial halo stars have chemical and kinematic/orbital quantities that associate them with the GES debris. Initial results suggest that these intermediate-age stars are not a product of mass transfer and/or stellar mergers, which can bias their age determination low. If this conclusion is upheld by upcoming spectrophotometric studies, then the presence of these stars will pose an important challenge for constraining the properties of the GES merger and the accretion history of the galaxy.

Keywords: Galaxy formation, Galaxy dynamics, Galaxy ages, Galaxy abundances, Galaxy accretion
The Rockets for Extended-source X-ray Spectroscopy Instrument Design. The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of suborbital rocket payloads designed to collect spectral emission from extended astronomical sources of soft X-rays. The tREXS spectrograph uses mechanical beam-shaping modules and reflection gratings to passively focus and then disperse incident X-rays to an array of Teledyne/e2v CIS 113 CMOS X-ray sensors. Designed to achieve a moderate spectral resolution, R ⪆ 50, from ≈15 to 40 Å over a large field of view (&gt;10 deg2), the tREXS instrument is sensitive to line emission from key ion species over the soft-X-ray band. Here we present the complete end-to-end design of the tREXS spectrograph and discuss its significance and expected performance, using simulated observations of the Cygnus Loop supernova remnant and an enhanced region in the soft X-ray background.

Keywords: Rockets, X-ray telescopes, Supernova remnants, Spectrometers, Astronomical techniques, Astronomical instrumentation, Spectroscopy, Diffuse x-ray background
Bayesian Constraints on the Ring Ellipticity of M87* 2017 Using THEMIS. Measuring the properties of black hole images has the potential to constrain deviations from general relativity on horizon scales. Of particular interest is the ellipticity of the ring that is sensitive to the underlying spacetime. In 2019, the Event Horizon Telescope (EHT) produced the first-ever image of a black hole on horizon scales. Here, we reanalyze the M87* EHT 2017 data using Bayesian imaging (BI) techniques, constructing a posterior of the ring shape. We find that BI recovers the true on-sky ring shape more reliably than the original imaging methods used in 2019. As a result, we find that M87*'s ring ellipticity is and is consistent with the measured ellipticity from general relativistic magnetohydrodynamic simulations.

Keywords: Supermassive black holes, Very long baseline interferometry, Astronomy data analysis
A Breakdown of the Black Hole–Bulge Mass Relation in Local Active Galaxies. We investigate the relation between black hole (BH) mass and bulge stellar mass for a sample of 117 local (z ∼ 0) galaxies hosting low-luminosity, broad-line active galactic nuclei (AGNs). Our sample comes from Reines &amp; Volonteri, who found that, for a given total stellar mass, these AGNs have BH masses more than an order of magnitude smaller than those in early-type galaxies with quiescent BHs. Here, we aim to determine whether or not this AGN sample falls on the canonical BH-to-bulge mass relation by utilizing bulge–disk decompositions and determining bulge stellar masses using color-dependent mass-to-light ratios. We find that our AGN sample remains offset by more than an order of magnitude from the M BH–M bulge relation defined by early-type galaxies with dynamically detected BHs. We caution that using canonical BH-to-bulge mass relations for galaxies other than ellipticals and bulge-dominated systems may lead to highly biased interpretations. This work bears directly on predictions for gravitational-wave detections and cosmological simulations that are tied to the local BH-to-bulge mass relations.

Keywords: Galaxy bulges, Active galaxies, Scaling relations, Seyfert galaxies, Active galactic nuclei
Flux Density Stability and Temporal Changes in the Spectra of Millisecond Pulsars Using the GMRT. This paper presents an investigation of the spectral properties of 10 millisecond pulsars (MSPs) discovered by the uGMRT, observed from 2017 to 2023 using band 3 (300–500 MHz) and 4 (550–750 MHz) of the uGMRT. For these MSPs, we have reported a range of spectral indices from ∼0 to ‑4.8, while averaging the full observing band and all the observing epochs. For every MSP, we calculated the mean flux density across 7–8 subbands, each with approximately 25 MHz bandwidth spanning band 3 and band 4. We computed their modulation indices as well as average and maximum-to-median flux density within each subband. Using the temporal variations of the flux density we calculated the refractive scintillation timescales and estimated a structure function with a time lag for eight MSPs in the sample. We note a significant temporal evolution of the in-band spectra, classified into three categories based on the nature of the best-fit power-law spectra, having single positive spectral indices, multiple broken power laws, and single negative spectral indices. Additionally, indications of a low-frequency turnover and temporal variations of the turnover frequency (to the extent that turnover was observed for some of the epochs while not seen for the rest) were noted for all the MSPs. To the best of our knowledge, this is the first systematic investigation probing temporal changes in MSP spectra as well as in the turnover frequency. Future exploration with dense monitoring combined with the modeling of spectra can provide vital insight into the intrinsic emission properties of MSPs and interstellar medium properties.

Keywords: Millisecond pulsars, Pulsars, Spectral index, Radio astronomy, Radio pulsars
Constraints on the Lyman Continuum Escape from Low-mass Lensed Galaxies at 1.3 ≤ z ≤ 3.0. Low-mass galaxies can significantly contribute to reionization due to their potentially high Lyman continuum (LyC) escape fraction and relatively high space density. We present a constraint on the LyC escape fraction from low-mass galaxies at z = 1.3–3.0. We obtained rest-frame UV continuum imaging with the ACS/SBC and the WFC3/UVIS from the Hubble Space Telescope for eight strongly lensed galaxies that were identified in the Sloan Giant Arc Survey and the Cluster Lensing and Supernova survey with Hubble. The targeted galaxies were selected to be spectroscopically confirmed, highly magnified, and blue in their UV spectral shapes (β &lt; ‑1.7). Our targets include intrinsically low-luminosity galaxies down to a magnification-corrected absolute UV magnitude M UV ∼ ‑14. We perform custom-defined aperture photometry to place the most reliable upper limits of LyC escape from our sample. From our observations, we report no significant (&gt;2σ) detections of LyC fluxes, placing 1σ upper limits on the absolute LyC escape fractions of 3%–15%. Our observations do not support the expected increased escape fractions of LyC photons from intrinsically UV faint sources. Considering the highly anisotropic geometry of LyC escape, increasing the sample size of faint galaxies in future LyC observations is crucial.

Keywords: Strong gravitational lensing, Dwarf galaxies, Ultraviolet astronomy, Extragalactic astronomy, Reionization
Unraveling the Mystery of the Low CO-to-H<SUB>2</SUB> Conversion Factor in Starburst Galaxies: RADEX Modeling of the Antennae. CO emission has been widely used as a tracer of molecular gas mass. However, it is a long-standing issue to accurately constrain the CO-to-H2 conversion factor (α CO) that converts CO luminosity to molecular gas mass, especially in starburst galaxies. We present the first resolved α CO modeling results with multiple Atacama Large Millimeter/submillimeter Array CO and 13CO transition observations at both giant molecular cloud (GMC) scale at 150 pc and kiloparsec scale for one of the closest starburst mergers, the Antennae. By combining our CO modeling results and measurements of 350 GHz dust continuum, we find that most GMCs in the Antennae have α CO values approximately four times smaller than the commonly adopted Milky Way value (4.3). We find that α CO at GMC scales shows a strong dependence on CO intensity, 13CO/CO ratio, and GMC velocity dispersion, which is consistent with various theoretical and simulation predictions. Specifically, we suggest that the 13CO/CO line ratio and the velocity dispersion can be used to infer α CO in starburst regions. By applying our modeled α CO in GMC analyses, we find that GMCs in the Antennae are less gravitationally bound than in normal spiral galaxies, which is more consistent with what is predicted by merger simulations. At kiloparsec scale, we find that our modeled α CO values are smaller than the modeled α CO at GMC scale by 40%, which can be due to inclusion of a diffuse gas component with lower α CO values. We find a similar correlation of α CO and CO intensity at kiloparsec scales to that at GMC scales.

Keywords: Molecular gas, Starburst galaxies, Molecular clouds, Galaxy mergers, CO line emission
Whistler Waves in the Young Solar Wind: Statistics of Amplitude and Propagation Direction from Parker Solar Probe Encounters 1─11. In the interplanetary space solar wind plasma, whistler waves are observed in a wide range of heliocentric distances (from ∼20 solar radii (RS) to Jupiter's orbit). They are known to interact with solar wind suprathermal electrons (strahl and halo) and to regulate the solar wind heat flux through scattering the strahl electrons. We present the results of applying the technique to determine the whistler wave propagation directions to the spectral data continuously collected by the FIELDS instruments on board Parker Solar Probe (PSP). The technique was validated based on the results obtained from burst mode magnetic and electric field waveform data collected during Encounter 1. We estimated the effective length of the PSP electric field antennas for a variety of solar wind conditions in the whistler wave frequency range and utilized these estimates for determining the whistler wave properties during PSP Encounters 1─11. Our findings show that (1) the enhancement of the whistler wave occurrence rate and wave amplitudes observed between 25 and 35 RS is predominantly due to the sunward-propagating whistler wave population associated with the switchback-related magnetic dips; (2) the antisunward or counterpropagating cases are observed at 30─40 RS; (3) between 40 and 50 RS, sunward and antisunward whistlers are observed with comparable occurrence rates; and (4) almost no sunward or counterpropagating whistlers were observed at heliocentric distances above 50 RS.

Keywords: Solar wind
The Fraction of Dust Mass in the Form of Polycyclic Aromatic Hydrocarbons on 10─50 pc Scales in Nearby Galaxies. Polycyclic aromatic hydrocarbons (PAHs) are a ubiquitous component of the interstellar medium (ISM) in z ∼ 0 massive, star-forming galaxies and play key roles in ISM energy balance, chemistry, and shielding. Wide field-of-view, high-resolution mid-infrared (MIR) images from JWST provide the ability to map the fraction of dust in the form of PAHs and the properties of these key dust grains at 10─50 pc resolution in galaxies outside the Local Group. We use MIR JWST photometric observations of a sample of 19 nearby galaxies from the Physics at High Angular Resolution in Nearby GalaxieS (PHANGS) survey to investigate the variations of the PAH fraction. By comparison to lower-resolution far-infrared mapping, we show that a combination of the MIRI filters (R PAH = [F770W+F1130W]/F2100W) traces the fraction of dust by mass in the form of PAHs (i.e., the PAH fraction, or q PAH). Mapping R PAH across the 19 PHANGS galaxies, we find that the PAH fraction steeply decreases in H II regions, revealing the destruction of these small grains in regions of ionized gas. Outside H II regions, we find R PAH is constant across the PHANGS sample with an average value of 3.43 ± 0.98, which, for an illuminating radiation field of intensity 2─5 times that of the radiation field in the solar neighborhood, corresponds to q PAH values of 3%─6%.

Keywords: Interstellar dust, Polycyclic aromatic hydrocarbons, Interstellar medium
The Relative Prevalence of Wave Packets and Coherent Structures in the Inertial and Kinetic Ranges of Turbulence as Seen by Solar Orbiter. The Solar Orbiter (SO) mission provides the opportunity to study the evolution of solar wind turbulence. We use SO observations of nine extended intervals of homogeneous turbulence to determine when turbulent magnetic field fluctuations may be characterized as: (i) wave packets and (ii) coherent structures (CSs). We perform the first systematic scale-by-scale decomposition of the magnetic field using two wavelets known to resolve wave packets and discontinuities, the Daubechies 10 (Db10) and Haar, respectively. The probability distribution functions (PDFs) of turbulent fluctuations on small scales exhibit stretched tails, becoming Gaussian at the outer scale of the cascade. Using quantile–quantile plots, we directly compare the wavelet fluctuations PDFs, revealing three distinct regimes of behavior. Deep within the inertial range (IR) both decompositions give essentially the same fluctuation PDFs. Deep within the kinetic range (KR) the PDFs are distinct as the Haar decompositions have larger variance and more extended tails. On intermediate scales, spanning the IR–KR break, the PDF is composed of two populations: a core of common functional form containing ∼97% of fluctuations, and tails that are more extended for the Haar decompositions than the Db10 decompositions. This establishes a crossover between wave-packet (core) and CS (tail) phenomenology in the IR and KR, respectively. The range of scales where the PDFs are two-component is narrow at 0.9 au (4–16 s) and broader (0.5–8 s) at 0.4 au. As CS and wave–wave interactions are both candidates to mediate the turbulent cascade, these results offer new insights into the distinct physics of the IR and KR.

Keywords: Heliosphere, Interplanetary turbulence, Solar wind, Wavelet analysis, Time series analysis
A Multiwavelength Machine-learning Approach to Classifying X-Ray Sources in the Fields of Unidentified 4FGL-DR4 Sources. A large fraction of Fermi-Large Area Telescope (LAT) sources in the fourth Fermi-LAT 14 yr catalog (4FGL) still remain unidentified (unIDed). We continued to improve our machine-learning pipeline and used it to classify 1206 X-ray sources with signal-to-noise ratios &gt;3 located within the extent of 73 unIDed 4FGL sources with Chandra X-ray Observatory observations included in the Chandra Source Catalog 2.0. Recent improvements to our pipeline include astrometric corrections, probabilistic cross-matching to lower-frequency counterparts, and a more realistic oversampling method. X-ray sources are classified into eight broad predetermined astrophysical classes defined in the updated training data set, which we also release. We present details of the machine-learning classification, describe the pipeline improvements, and perform an additional spectral and variability analysis for brighter sources. The classifications give 103 plausible X-ray counterparts to 42 GeV sources. We identify 2 GeV sources as isolated neutron star candidates, 16 as active galactic nucleus candidates, seven as sources associated with star-forming regions, and eight as ambiguous cases. For the remaining 40 unIDed 4FGL sources, we could not identify any plausible counterpart in X-rays, or they are too close to the Galactic Center. Finally, we outline the observational strategies and further improvements in the pipeline that can lead to more accurate classifications.

Keywords: Neutron stars, Astrostatistics tools, X-ray binary stars, Astronomical object identification, Classification, Gamma-ray sources, Active galactic nuclei, X-ray surveys, X-ray sources, Compact objects, Random Forests, Catalogs
Ionized and Cold Gas Components in Low Surface Brightness Galaxy AGC 102004. We present the integral field spectroscopic observations of ionized gas (Hα and [N II]) using the PCWI, along with deep CO(2–1) observations by the  ‵U¯‵u¯  receiver on JCMT for AGC 102004. The velocity field of Hα shows an anomalous distribution in the northwestern (NW) disk. The Hα spectrum is well-fitted by two Gaussian components, and the weak Gaussian component is dominated by the anomalous Hα in the NW disk. The Gaussian fit center of Hα emission is offset by +24.2 km s‑1 from the systemic velocity obtained from the H I emission. We derive the gas-phase metallicity, 12+log(O/H), using [N II]λ6583/Hα ratio as a proxy. The mean value of 12+log(O/H) is 8.30 ± 0.19 over the whole galaxy. The metallicity in the outer disk is lower than the detection limit of 7.72, indicating the metallicity gradient exists in AGC 102004. We speculate a minor/mini-merger event could have happened to the NW disk. CO(2–1) emission has nondetection in AGC 102004, reaching a noise level of 0.33 mK smoothed to 30 km s‑1. The upper limit of molecular gas mass in AGC 102004 is 2.1 × 107 M ⊙ with X CO = 3.02 × 1020 cm‑2 (K km s‑1)‑1. The  MH2 /M  HIcorr  of AGC 102004 is lower than 0.0037 and lower than that of normal galaxies.

Keywords: Molecular gas, Metallicity, Galaxy mergers, Low surface brightness galaxies
Merger Shocks Enhance Quenching in Local Galaxy Clusters. We report evidence for enhanced quenching in low-redshift galaxy clusters hosting radio relics. This effect is strongest for low-mass galaxies and is consistent with a rapid quenching of star formation. These results imply that merger shocks in the intracluster medium play a role in driving environmental quenching, which we argue is due to elevated ram pressure in these disturbed systems.

Keywords: Galaxy clusters, Star formation, Galaxy evolution, Radio continuum emission, Galaxy quenching
Resonant Absorption of Standing Magnetohydrodynamic Waves in Coronal Loops in the Absence of Directional Symmetry: The Effect of Plasma Flow. The oscillation properties of standing magnetohydrodynamic (MHD) waves in coronal loops have been investigated. The coronal loop is modeled as a straight cylinder with a purely longitudinal magnetic field and a field-aligned plasma flow. The loop model includes an inhomogeneous transitional layer that causes the wave to be resonantly damped. Our aim is to determine the damping rate of the standing MHD waves in flowing loops, in which the directional symmetry of the loop has been broken due to the presence of plasma flow. To do this, the standing wave has been considered as the superposition of two propagating waves with opposite directions of propagation but the same oscillation frequency and damping rate. Due to the absence of directional symmetry in the loop, it seems that the propagating components of the standing wave cannot have the same oscillation frequency and damping rate. To overcome this problem, in the perturbation method employed, we let both the oscillation frequency and damping rate be perturbed. As the flow speed increases the oscillation frequency of the standing wave decreases but its damping rate increases. As a result, the ratio of the oscillation frequency to the damping rate of the standing wave becomes a more decreasing function of the flow speed. The flow is an important quantity in determining the effectiveness of resonant absorption. In flowing loops even in the case of a thin transitional layer, resonant absorption can result in a damping rate on the order of the period time, which is in agreement with observations.

Keywords: Solar atmosphere, The Sun, Solar coronal waves