Sazuna/UAT_keywords huggingface dataset:
Tracing Interstellar Heating: An ALCHEMI Measurement of the HCN Isomers in NGC 253. We analyze HCN and HNC emission in the nearby starburst galaxy NGC 253 to investigate its effectiveness in tracing heating processes associated with star formation. This study uses multiple HCN and HNC rotational transitions observed using the Atacama Large Millimeter/submillimeter Array via the ALCHEMI Large Program. To understand the conditions and associated heating mechanisms within NGC 253's dense gas, we employ Bayesian nested sampling techniques applied to chemical and radiative transfer models, which are constrained using our HCN and HNC measurements. We find that the volume density ${n}_{{{\rm{H}}}_{2}}$ and cosmic-ray ionization rate (CRIR) ζ are enhanced by about an order of magnitude in the galaxy's central regions as compared to those further from the nucleus. In NGC 253's central giant molecular clouds (GMCs), where observed HCN/HNC abundance ratios are the lowest, n ~ 105.5 cm-3 and ζ ~ 10-12 s-1 (greater than 104 times the average Galactic rate). We find a positive correlation in the association of both density and CRIR with the number of star formation-related heating sources (supernova remnants, H II regions, and super hot cores) located in each GMC, as well as a correlation between CRIRs and supernova rates. Additionally, we see an anticorrelation between the HCN/HNC ratio and CRIR, indicating that this ratio will be lower in regions where ζ is higher. Though previous studies suggested HCN and HNC may reveal strong mechanical heating processes in NGC 253's CMZ, we find cosmic-ray heating dominates the heating budget, and mechanical heating does not play a significant role in the HCN and HNC chemistry.

Keywords: Interstellar molecules, Starburst galaxies, Spiral galaxies, Star forming regions, Active galaxies, Astrochemistry, Galaxy nuclei, Star formation, Cosmic rays
Isolated Massive Star Formation in G28.20-0.05. We report high-resolution 1.3 mm continuum and molecular line observations of the massive protostar G28.20-0.05 with Atacama Large Millimeter/submillimeter Array. The continuum image reveals a ring-like structure with 2000 au radius, similar to morphology seen in archival 1.3 cm Very Large Array observations. Based on its spectral index and associated H30α emission, this structure mainly traces ionized gas. However, there is evidence for ~30 M ⊙ of dusty gas near the main millimeter continuum peak on one side of the ring, as well as in adjacent regions within 3000 au. A virial analysis on scales of ~2000 au from hot core line emission yields a dynamical mass of ~80 M ⊙. A strong velocity gradient in the H30α emission is evidence for a rotating, ionized disk wind, which drives a larger-scale molecular outflow. An infrared spectral energy distribution (SED) analysis indicates a current protostellar mass of m * ~ 40 M ⊙ forming from a core with initial mass M  c  ~ 300 M ⊙ in a clump with mass surface density of Σcl ~ 0.8 g cm-2. Thus the SED and other properties of the system can be understood in the context of core accretion models. A structure-finding analysis on the larger-scale continuum image indicates G28.20-0.05 is forming in a relatively isolated environment, with no other concentrated sources, i.e., protostellar cores, above ~1 M ⊙ found from ~0.1 to 0.4 pc around the source. This implies that a massive star can form in relative isolation, and the dearth of other protostellar companions within the ~1 pc environs is a strong constraint on massive star formation theories that predict the presence of a surrounding protocluster.

Keywords: Massive stars, Star formation, Interstellar medium, Star forming regions
Power Anisotropy, Dispersion Signature and Turbulence Diffusion Region in the 3D Wavenumber Domain of Space Plasma Turbulence. We explore the multifaceted important features of turbulence (e.g., anisotropy, dispersion, and diffusion) in the three-dimensional (3D) wavenumber domain (k ∥, k ⊥,1, k ⊥,2), by employing the k-filtering technique to high-quality measurements of fields and particles from the Magnetospheric Multiscale Mission (MMS) multi-spacecraft constellation. We compute the 3D power spectral densities (PSDs) of magnetic and electric field fluctuations (marked as PSD(δ B ( k )) and $\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\langle {{\boldsymbol{v}}}_{{\rm{i}}}\rangle }^{{\prime} }({\boldsymbol{k}}))$ , respectively), both of which show a prominent spectral anisotropy in the sub-ion range. We give the first 3D image of the bifurcation between the power spectra of the electric and magnetic fluctuations, by calculating the ratio between $\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\langle {{\boldsymbol{v}}}_{{\rm{i}}}\rangle }^{{\prime} }({\boldsymbol{k}}))$ and PSD(δ B ( k )), the distribution of which is related to the nonlinear dispersion relation. We also compute the ratio between electric spectra in different reference frames defined by the ion bulk velocity, $\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\mathrm{local}\ {{\boldsymbol{v}}}_{{\rm{i}}}}^{{\prime} })/\mathrm{PSD}(\delta {{\boldsymbol{E}}}_{\langle {{\boldsymbol{v}}}_{{\rm{i}}}\rangle }^{{\prime} })$ , to visualize the turbulent ion diffusion region (T-IDR) in wavenumber space. The T-IDR has an anisotropy and a preferential direction of wavevectors, which is generally consistent with the plasma wave theory prediction based on the dominance of kinetic Alfvén waves. This work demonstrates the worth of the k-filtering technique in diagnosing turbulence comprehensively, especially when the electric field is involved.

Keywords: Interplanetary turbulence, Space plasmas, Solar wind
Experimental Determination of the Dissociative Recombination Rate Coefficient for Rotationally Cold CH<SUP>+</SUP> and Its Implications for Diffuse Cloud Chemistry. Observations of CH+ are used to trace the physical properties of diffuse clouds, but this requires an accurate understanding of the underlying CH+ chemistry. Until this work, the most uncertain reaction in that chemistry was dissociative recombination (DR) of CH+. Using an electron-ion merged-beams experiment at the Cryogenic Storage Ring, we have determined the DR rate coefficient of the CH+ electronic, vibrational, and rotational ground state applicable for different diffuse cloud conditions. Our results reduce the previously unrecognized order-of-magnitude uncertainty in the CH+ DR rate coefficient to ~20% and are applicable at all temperatures relevant to diffuse clouds, ranging from quiescent gas to gas locally heated by processes such as shocks and turbulence. Based on a simple chemical network, we find that DR can be an important destruction mechanism at temperatures relevant to quiescent gas. As the temperature increases locally, DR can continue to be important up to temperatures of ~600 K, if there is also a corresponding increase in the electron fraction of the gas. Our new CH+ DR rate-coefficient data will increase the reliability of future studies of diffuse cloud physical properties via CH+ abundance observations.

Keywords: Laboratory astrophysics, Diffuse molecular clouds, Reaction rates, Electron recombination reactions
Hunting for Neutrino Emission from Multifrequency Variable Sources. Pinpointing the neutrino sources is crucial to unveil the mystery of high-energy cosmic rays. The search for neutrino source candidates from coincident neutrino-photon signatures and objects with particular electromagnetic flaring behaviors can increase our chances of finding neutrino emitters. In this paper, we first study the temporal correlations of astrophysical flares with neutrinos, considering a few hundred multifrequency sources from the Atacama Large Millimeter/submillimeter Array, the Wide-field Infrared Survey Explorer (WISE), Swift, and Fermi in the containment regions of IceCube high-energy alerts. Furthermore, the spatial correlations between blazars and neutrinos are investigated using the subset of 10 yr IceCube track-like neutrinos with around 250,000 events. In a second test, we account for 2700 blazars with different types of flaring stages in addition to their position. No significant neutrino emissions were found from our analyses. Our results indicate an interesting trend showing that the infrared flaring phases of WISE blazars might be correlated with the arrival times of the neutrino alerts. A possible overflow of neutrinos associated with two of our selected blazar samples is discussed in detail. One is characterized by a significant flaring lag in infrared with respect to γ-rays, as seen for TXS 0506+056, and the other is characterized by highly simultaneous infrared and γ-ray flares. Our investigation suggests the need to improve current multifrequency light-curve catalogs to pair with the advent of more sensitive neutrino observatories.

Keywords: High energy astrophysics, Blazars, Light curves, Neutrino astronomy, Active galactic nuclei
Investigating the [C II]-to-H I Conversion Factor and the H I Gas Budget of Galaxies at z ≈ 6 with Hydrodynamic Simulations. One of the most fundamental baryonic matter components of galaxies is the neutral atomic hydrogen (H I). At low redshifts, this component can be traced directly through the 21 cm transition, but to infer the H I gas content of the most distant galaxies, a viable tracer is needed. We here investigate the fidelity of the fine-structure transition of the (2 P 3/2 - 2 P 1/3) transition of singly ionized carbon C II at 158 μm as a proxy for H I in a set simulated galaxies at z ≈ 6, following the work by Heintz et al. We select 11,125 star-forming galaxies from the SIMBA simulations, with far-infrared line emissions postprocessed and modeled within the SIGAME framework. We find a strong connection between C II and H I, with the relation between this C II-to-H I relation (β [C II]) being anticorrelated with the gas-phase metallicity of the simulated galaxies. We further use these simulations to make predictions for the total baryonic matter content of galaxies at z ≈ 6, and specifically the H I gas mass fraction. We find mean values of M H I/M ⋆ = 1.4 and M H I/M bar,tot = 0.45. These results provide strong evidence for H I being the dominant baryonic matter component by mass in galaxies at z ≈ 6.

Keywords: Interstellar medium, High-redshift galaxies, Astronomical simulations, Interstellar atomic gas
Corrections to Estimated Accretion Disk Size due to Color Correction, Disk Truncation, and Disk Wind. We consider three corrections to the disk sizes estimated at a given frequency using accretion models. They are due to a color correction, a disk truncation at an inner radius larger than the innermost stable circular orbit, and disk winds, which we apply to the standard disk model. We apply our results to the estimates of the disk sizes based on microlensing. We find that these three effects combined can explain the long-standing problem of the disk sizes from microlensing being larger than those estimated using the standard disk model (i.e., that without accounting for the above effects). In particular, an increase of the color correction with the increasing temperature can lead to a strong increase of the half-light radius even if this correction is close to unity at the temperature corresponding to an observed frequency. Our proposed formalism for calculating the half-light radius also resolves the long-standing issue of discrepancies between the disk size estimates based on the accretion rate and on the observed flux.

Keywords: Accretion, Galaxy accretion disks, Active galactic nuclei, Gravitational microlensing
Metallicities of Five z &gt; 5 Emission-line Galaxies in SMACS 0723 Revealed by JWST. JWST's Early Release Observations of the lensing cluster SMACS J0723.3-7327 have given an unprecedented spectroscopic look into the high-redshift universe. These observations reveal five galaxies at z &gt; 5. All five have detectable [O III]λ4363 line emission, indicating that these galaxies have high temperatures and low metallicities and that they are highly star-forming. In recent work, the metallicities of these five galaxies have been studied using various techniques. Here we summarize and compare these previous results, as well as perform our own measurements of the metallicities using improved methodologies that optimize the extraction of the emission lines. In particular, we use simultaneous line fitting and a fixed Balmer decrement correction, as well as a novel footprint measurement of the emission lines in the 2D spectra, to produce higher-fidelity line ratios that are less sensitive to calibration and systematic effects. We then compare our metallicities to those of z ≲ 1 galaxies with high rest-frame equivalent widths of Hβ, finding that they may be good analogs. Finally, we estimate that the JWST galaxies out to z ~ 8 are young compared to the age of the universe.

Keywords: Metallicity, Galaxy spectroscopy, High-redshift galaxies, Emission line galaxies
First AI for Deep Super-resolution Wide-field Imaging in Radio Astronomy: Unveiling Structure in ESO 137-006. We introduce the first AI-based framework for deep, super-resolution, wide-field radio interferometric imaging and demonstrate it on observations of the ESO 137-006 radio galaxy. The algorithmic framework to solve the inverse problem for image reconstruction builds on a recent "plug-and-play" scheme whereby a denoising operator is injected as an image regularizer in an optimization algorithm, which alternates until convergence between denoising steps and gradient-descent data fidelity steps. We investigate handcrafted and learned variants of high-resolution, high dynamic range denoisers. We propose a parallel algorithm implementation relying on automated decompositions of the image into facets and the measurement operator into sparse low-dimensional blocks, enabling scalability to large data and image dimensions. We validate our framework for image formation at a wide field of view containing ESO 137-006 from 19 GB of MeerKAT data at 1053 and 1399 MHz. The recovered maps exhibit significantly more resolution and dynamic range than CLEAN, revealing collimated synchrotron threads close to the galactic core.

Keywords: Computational astronomy, Aperture synthesis, Convolutional neural networks, Radio galaxies, Astronomy image processing
VLBA Reveals the Absence of a Compact Radio Core in the Radio-intermediate Quasar J2242+0334 at z = 5.9. High-resolution imaging is crucial for exploring the origin and mechanism of radio emission in quasars, especially at high redshifts. We present 1.5 GHz Very Long Baseline Array (VLBA) images of the radio continuum emission from the radio-intermediate quasar (RIQ) J2242+0334 at z = 5.9. This object was previously detected at both 1.5 GHz and 3 GHz with the Karl G. Jansky Very Large Array (VLA) as a point source. However, there is no clear detection in the VLBA images at both the full resolution of 10.7 mas × 4.5 mas (61.7 pc × 26.0 pc) and a tapered resolution of 26 mas × 21 mas (150 pc × 121 pc). This suggests that the radio emission from the quasar is diffuse on milliarcsecond scales with surface brightness fainter than the 3σ detection limit of 40.5 μJy beam-1 in the full-resolution image. The radio emission in the RIQ J2242+0334 is likely to be wind-like (i.e., diffuse) rather than in the form of collimated jets. This is different from the previous radio detections of the most luminous quasars at z ~ 6 that are usually dominated by compact, high brightness temperature radio sources. Meanwhile, compared with RIQs at low redshifts, the case of J2242+0334 suggests that not all RIQs are beamed radio-quiet quasars. This optically faint RIQ provides an important and unique example to investigate the radio activity in the less powerful active galactic nuclei at the earliest cosmic epoch.

Keywords: Radio continuum emission, Early universe, Quasars
First Millimeter Flares Detected from ϵ Eridani with the Atacama Large Millimeter/submillimeter Array. We report the detection of three large millimeter flaring events from the nearby Sun-like, ϵ Eridani, found in archival Atacama Large Millimeter/submillimeter Array (ALMA) 12 m and Atacama Compact Array observations at 1.33 mm taken from 2015 January 17 to 18 and 2016 October 24 to November 23, respectively. This is the first time that flares have been detected from a Sun-like star at millimeter wavelengths. The largest flare among our data was detected in the ALMA observations on 2015 January 17 from 20:09:10.4-21:02:49.3 UT with a peak flux density of 28 ± 7 mJy and a duration of 9 s. The peak brightness of the largest flare is 3.4 ± 0.9 × 1014 erg s-1 Hz-1, a factor of &gt;50× times brighter than the star's quiescent luminosity and &gt;10× brighter than solar flares observed at comparable wavelengths. We find changes in the spectral index (F ν  ∝ ν  α ) at the flare peak, with α = 1.81 ± 1.94 and a lower limit on the fractional linear polarization ∣Q/I∣ = 0.08 ± 0.12. This positive spectral index is more similar to millimeter solar flares, differing from M-dwarf flares also detected at millimeter wavelengths that exhibit steeply negative spectral indices.

Keywords: Debris disks, Stellar activity, Stellar flares, Circumstellar disks, Submillimeter astronomy, Radio astronomy
JWST Sneaks a Peek at the Stellar Morphology of z 2 Submillimeter Galaxies: Bulge Formation at Cosmic Noon. We report morphological analyses of seven submillimeter galaxies (SMGs) at z ~ 2 using the James Webb Space Telescope NIRCam images taken as part of the public CEERS and PRIMER surveys. Through two-dimensional surface brightness profile fitting we find evidence of compact reddened stellar structures in all the SMGs, in particular in the F444W filter, suggesting an ubiquitous presence of stellar bulges. The median size of these bulges at F444W with a bootstrapped uncertainty is found to be 0.7 ± 1.0 kpc (0.6-0.7-3.9 kpc for 14th-50th-86th percentiles) and the median Sérsic index is 0.7 ± 0.9 (0.4-0.7-2.8 for 14th-50th-86th percentiles). Structures akin to spiral arms and bars are also identified, and their asymmetric shapes, tidal features, as well as evidence of nearby galaxies at consistent redshifts as those of corresponding SMGs suggest that these SMGs are undergoing dynamical interactions, likely responsible for the triggering of their star-forming activity. Via a curve-of-growth analysis we deduce half-light radii for the NIRCam wave bands, finding that sizes are significantly smaller at longer wavelengths in all cases, in particular that the median size ratio between F444W and F150W is 0.6 ± 0.1. However, we also find that F444W sizes, roughly corresponding to rest-frame H band, are not smaller than those of submillimeter continuum as measured by the Atacama Large Millimeter/submillimeter Array, contradicting certain recent predictions from theoretical models. Our results suggest that while stellar bulges are undergoing an active formation phase in SMGs at z ~ 2, the total stellar masses of SMGs are still dominated by their disks, not bulges.

Keywords: Galaxy formation, Galaxy structure, Galaxy interactions, Ultraluminous infrared galaxies, High-redshift galaxies
Hubble Space Telescope Reveals Spectacular Light Echoes Associated with the Stripped-envelope Supernova 2016adj in the Iconic Dust Lane of Centaurus A. We present a multiband sequence of Hubble Space Telescope images documenting the emergence and evolution of multiple light echoes (LEs) linked to the stripped-envelope supernova (SN) 2016adj located in the central dust lane of Centaurus A. Following point-spread function subtraction, we identify the earliest LE emission associated with an SN at only +34 days past the epoch of the B-band maximum. Additional HST images extending through +578 days cover the evolution of LE1 taking the form of a ring, while images taken on +1991 days reveal not only LE1 but also segments of a new inner LE ring (LE2) as well as two additional outer LE rings (LE3 and LE4). Adopting the single-scattering formalism, the angular radii of the LEs suggest they originate from discrete dust sheets in the foreground of the SN. This information, combined with measurements of color and optical depth of the scattering surfaces, informs a scenario with multiple sheets of clumpy dust characterized by a varying degree of holes. In this case, the larger the LE's angular radii, the farther in the foreground of the SN its dust sheet is located. However, an exception to this is LE2, which is formed by a dust sheet located in closer proximity to the SN than the dust sheets producing LE1, LE3, and LE4. The delayed appearance of LE2 can be attributed to its dust sheet having a significant hole along the line of sight between the SN and Earth.

Keywords: Type Ic supernovae, Core-collapse supernovae
Spectral Evolution of Dark Asteroid Surfaces Induced by Space Weathering over a Decade. The surfaces of airless bodies like asteroids in the solar system are known to be affected by space weathering. Experiments simulating space weathering are essential for studying the effects of this process on meteorite samples, but the problem is that the time spent to reproduce space weathering in these experiments is billions of times shorter than the actual phenomenon. In 2010 December, the T-type asteroid 596 Scheila underwent a collision with an impactor a few tens of meters in size. A decade later, there is an opportunity to study how the surface layer of this asteroid is being altered by space weathering after the impact. To do so, we performed visible spectrophotometric and near-infrared spectroscopic observations of 596 Scheila. The acquired spectrum is consistent with those observed shortly after the 2010 impact event within the observational uncertainty range. This indicates that the surface color of dark asteroids is not noticeably changed by space weathering over a 10 yr period. This study is the first to investigate color changes due to space weathering on an actual asteroid surface in the solar system. Considering that fresh layers are regularly created on asteroid surfaces by collisions, we suggest a genetic link between D/T-type and dark (low albedo) X-complex asteroids and very red objects such as 269 Justitia, 732 Tjilaki, and 203 Pompeja. New observations show that 203 Pompeja has an X-type-like surface, with some local surface areas exhibiting a very red spectrum.

Keywords: Main belt asteroids, Asteroids, Small Solar System bodies, Asteroid surfaces
Most Planets Might Have More than 5 Myr of Time to Form. The lifetime of protoplanetary disks is a crucial parameter for planet formation research. Observations of disk fractions in star clusters imply median disk lifetimes of 1-3 Myr. This very short disk lifetime calls for planet formation to occur extremely rapidly. We show that young, distant clusters (≤5 Myr, &gt;200 pc) often dominate these types of studies. Such clusters frequently suffer from limiting magnitudes leading to an over-representation of high-mass stars. As high-mass stars disperse their disks earlier, the derived disk lifetimes apply best to high-mass stars rather than low-mass stars. Including only nearby clusters (&lt;200 pc) minimizes the effect of limiting magnitude. In this case, the median disk lifetime of low-mass stars is with 5-10 Myr, thus much longer than often claimed. The longer timescales provide planets ample time to form. How high-mass stars form planets so much faster than low-mass stars is the next grand challenge.

Keywords: Exoplanets, Young star clusters, Protoplanetary disks, Planet formation