Sazuna/UAT_keywords huggingface dataset:
On the Flux–Intensity Relation of Molecular Clouds. In this work, we report a study on the relationship between flux and intensity for molecular clouds. Our analysis is established on high-quality CO images from the Milky Way Imaging Scroll Painting project. The new flux–intensity relation characterizes the flux variation of molecular clouds above specific intensity levels. We found that the flux–intensity relation exhibits two prominent features. First, the flux–intensity relation generally follows exponential shapes; second, hierarchical structures of molecular clouds are imprinted on flux–intensity relations. Specifically, 12CO flux–intensity relations are composed of one or more exponential segments, and for molecular clouds with segmented flux–intensity relations, the edge and the flux of the high-temperature component are strikingly consistent with 13CO emission. Further analysis shows that a similar relationship also exists between 13CO flux–intensity relations and C18O emission. The mean brightness temperature of molecular clouds is tightly associated with the decay rate of flux, the break temperature of exponential segments, and, to a certain extent, the flux fraction of the high-temperature component. Broadly, the flux–intensity relation of a molecular tracer, either in optically thick or in optically thin cases, has the capability to outline the silhouette of internal structures of molecular clouds, proving to be a potent tool for probing structures of molecular clouds.

Keywords: Observational astronomy, Astrostatistics techniques, Molecular spectroscopy, Astronomy data analysis, Molecular clouds
JWST Reveals a Surprisingly High Fraction of Galaxies Being Spiral-like at 0.5 ≤ z ≤ 4. Spiral arms are one of the most important features used to classify the morphology of local galaxies. The cosmic epoch when spiral arms first appeared contains essential clues to the evolution of disk galaxies. In this Letter, we used James Webb Space Telescope images from the Cosmic Evolution Early Release Science Survey to visually identify spiral galaxies with redshift 0.5 ≤ z ≤ 4 and stellar mass ≥1010 M ⊙. Out of 873 galaxies, 216 were found to have a spiral structure. The spiral galaxies in our sample have higher star formation rates and larger sizes than nonspiral galaxies. We found the observed spiral fraction decreases from 48% at z ∼ 0.75 to 8% at z ∼ 2.75. These fractions are higher than the fractions observed with the Hubble Space Telescope. We even detect possible spiral-like features at redshifts z &gt; 3. We artificially redshifted low-redshift galaxies to high redshifts and reinspected them to evaluate observational effects. By varying the input spiral fraction of the redshifted sample, we found that the input fraction of ∼35% matches the observed fraction at z = 2–3 the best. We are able to rule out spiral fractions being &lt;20% (2σ) and &lt;10% (3σ) for real galaxies at z ∼ 3. This fraction is surprisingly high and implies that the formation of spiral arms, as well as disks, was earlier in the Universe.

Keywords: Spiral galaxies, Disk galaxies, Galaxy structure, Spiral arms, Galaxy evolution, Extragalactic astronomy, High-redshift galaxies, Galaxies
Probing the C IV Continuum Size–Luminosity Relation in Active Galactic Nuclei with Photometric Reverberation Mapping. Reverberation mapping accurately determines virial black hole masses only for redshifts z &lt; 0.2 by utilizing the relationship between the Hβ broad-line region (BLR) size and the 5100 Å continuum luminosity established with ∼200 active galactic nuclei. For quasars at z ∼ 2–3 determining the BLR size is time-consuming and limited by seasonal gaps, requiring, e.g., ∼20 yr of monitoring of the C IV emission lines. In this work, we demonstrate that an efficient alternative is to use a continuum size–luminosity relation, which can be obtained up to 150 times faster than BLR sizes using photometric reverberation mapping (PRM). We outline the method and its feasibility based on simulations and propose an observational strategy that can be carried out with meter-class telescopes. In particular, we focus on the ESO La Silla 2.2 m telescope as it is suitable for an efficient PRM campaign. These observations will provide the scaling factor between the accretion disk and the BLR size (for C IV-1350 Å), which is crucial for estimating the masses of black holes at higher redshifts (z ≳ 2–3).

Keywords: High-luminosity active galactic nuclei, Quasars, Reverberation mapping, Medium band photometry, Active galactic nuclei, Time domain astronomy, High-redshift galaxies, Time series analysis, Near infrared astronomy
Dissecting the Crab Nebula with JWST: Pulsar Wind, Dusty Filaments, and Ni/Fe Abundance Constraints on the Explosion Mechanism. We present JWST observations of the Crab Nebula, the iconic remnant of the historical SN 1054. The observations include NIRCam and MIRI imaging mosaics plus MIRI/MRS spectra that probe two select locations within the ejecta filaments. We derive a high-resolution map of dust emission and show that the grains are concentrated in the innermost, high-density filaments. These dense filaments coincide with multiple synchrotron bays around the periphery of the Crab's pulsar wind nebula (PWN). We measure synchrotron spectral index changes in small-scale features within the PWN's torus region, including the well-known knot and wisp structures. The index variations are consistent with Doppler boosting of emission from particles with a broken power-law distribution, providing the first direct evidence that the curvature in the particle injection spectrum is tied to the acceleration mechanism at the termination shock. We detect multiple nickel and iron lines in the ejecta filaments and use photoionization models to derive nickel-to-iron abundance ratios that are a factor of 3–8 higher than the solar ratio. We also find that the previously reported order-of-magnitude higher Ni/Fe values from optical data are consistent with the lower values from JWST when we reanalyze the optical emission using updated atomic data and account for local extinction from dust. We discuss the implications of our results for understanding the nature of the explosion that produced the Crab Nebula and conclude that the observational properties are most consistent with a low-mass Fe core-collapse supernova, even though an electron-capture explosion cannot be ruled out.

Keywords: Core-collapse supernovae, Pulsars, Supernova remnants, Pulsar wind nebulae, Supernovae
Deep Search for Phosphine in a Prestellar Core. Understanding in which chemical forms phosphorus exists in star- and planet-forming regions and how phosphorus is delivered to planets are of great interest from the viewpoint of the origin of life on Earth. Phosphine (PH3) is thought to be a key species to understanding phosphorus chemistry, but never has been detected in star- and planet-forming regions. We performed sensitive observations of the ortho-PH3 10 ‑ 00 transition (266.944 GHz) toward the low-mass prestellar core L1544 with the Atacama Compact Array stand-alone mode of the Atacama Large Millimeter/submillimeter Array. The line was not detected down to 3σ levels in 0.07 km s‑1 channels of 18 mK. The nondetection provides the upper limit to the gas-phase PH3 abundance of 5 × 10‑12 with respect to H2 in the central part of the core. Based on the gas-ice astrochemical modeling, we find the scaling relationship between the gas-phase PH3 abundance and the volatile (gas and ice with larger volatility than water) P elemental abundance for given physical conditions. This characteristic and well-constrained physical properties of L1544 allow us to constrain the upper limit to the volatile P elemental abundance of 5 × 10‑9, which is a factor of 60 lower than the overall P abundance in the interstellar medium. Then the majority of P should exist in refractory forms. The volatile P elemental abundance of L1544 is smaller than that in the coma of comet 67P/C-G, implying that the conversion of refractory phosphorus to volatile phosphorus could have occurred along the trail from the presolar core to the protosolar disk through, e.g., sputtering by accretion/outflow shocks.

Keywords: Interstellar molecules, Interstellar medium, Astrochemistry
Source Region of the Solar Wind: Statistics of the Doppler Velocities at the Chromosphere. The solar wind has been extensively studied recently with in situ observations, and the understanding of its counterpart near the solar surface has also progressed significantly. With the spectroscopic observations from the Chinese Hα Solar Explorer (CHASE), the chromospheric Dopplergram of the full solar disk is first obtained almost simultaneously. By investigating the statistics of the Doppler velocities at the chromosphere, we find that the coronal hole (CH) regions are dominated by Doppler blueshifts, with a stronger net magnetic flux region corresponding to smaller blueshift velocity. In addition to the average blueshift, the probability density of the Doppler shift is not symmetrically distributed but shows an excess at the redshift side, while the reference region does not show such an asymmetry. The redshift asymmetry may provide a possible clue for the interchange reconnection that might happen just above the chromosphere. By sampling the regions at the network boundaries in the CHs, the probability density is slightly enhanced at the parts of both larger blueshifts and redshifts compared with the result for the whole CH region. As the reference region also shows such enhancement, the crucial area associated with the origin of solar wind is not identified efficiently by sampling the overall network boundaries as demonstrated here. The present study shows the first attempt at interpreting the origin of solar wind in the transient CHs based on the CHASE spectroscopic observations, and a combination of full-disk and high-resolution observations is helpful in the future for firmly understanding the source region of solar wind.

Keywords: Quiet solar chromosphere, Solar wind, Solar corona, Solar magnetic fields, Solar coronal holes
Low-mass Galaxy Interactions Trigger Black Hole Activity. The existence of high-z overmassive supermassive black holes represents a major conundrum in our understanding of black hole evolution. In this Letter, we probe from the observational point of view how early Universe environmental conditions could have acted as an evolutionary mechanism for the accelerated growth of the first black holes. Under the assumption that the early Universe is dominated by dwarf galaxies, we investigate the hypothesis that dwarf–dwarf galaxy interactions trigger black hole accretion. We present the discovery of 82 dwarf–dwarf galaxy pairs and 11 dwarf galaxy groups using the Hubble Space Telescope, doubling existing samples. The dwarf systems span a redshift range of 0.13 &lt; z &lt; 1.5, and a stellar mass range of 7.24 &lt; log(M */M ⊙) &lt; 9.73. We performed an X-ray study of a subset of these dwarf systems with Chandra and detected six new active galactic nuclei (AGN), increasing the number of known dwarf–dwarf-merger-related AGN from one to seven. We then compared the frequency of these AGN in grouped/paired dwarfs to that of isolated dwarfs and found a statistically significant enhancement (4σ–6σ) in the interacting sample. This study, the first of its kind at the lowest mass scales, implies that the presence of a nearby dwarf neighbor is efficient in triggering black hole accretion. These results open new avenues for indirect studies of the emergence of the first supermassive black holes.

Keywords: Supermassive black holes, Dwarf galaxies, Active galactic nuclei, Galaxy mergers
LHS 1140 b Is a Potentially Habitable Water World. LHS 1140 b is a small planet orbiting in the habitable zone of its M4.5V dwarf host. Recent mass and radius constraints have indicated that it has either a thick H2-rich atmosphere or substantial water by mass. Here we present a transmission spectrum of LHS 1140 b between 1.7 and 5.2 μm, obtained using the NIRSpec instrument on JWST. By combining spectral retrievals and self-consistent atmospheric models, we show that the transmission spectrum is inconsistent with H2-rich atmospheres with varied size and metallicity, leaving a water world as the remaining scenario to explain the planet's low density. Specifically, a H2-rich atmosphere would result in prominent spectral features of CH4 or CO2 on this planet, but they are not seen in the transmission spectrum. Instead, the data favor a high mean molecular weight atmosphere (possibly N2 dominated with H2O and CO2) with a modest confidence. Forming the planet by accreting C- and N-bearing ices could naturally give rise to a CO2- or N2-dominated atmosphere, and if the planet evolves to or has the climate-stabilizing mechanism to maintain a moderate-size CO2/N2-dominated atmosphere, the planet could have liquid-water oceans. Our models suggest CO2 absorption features with an expected signal of 20 ppm at 4.2 μm. As the existence of an atmosphere on TRAPPIST-1 planets is uncertain, LHS 1140 b may well present the best current opportunity to detect and characterize a habitable world.

Keywords: Exoplanet atmospheric composition , Bayesian statistics, Exoplanets, Astronomy data analysis, Transmission spectroscopy, Atmospheric composition, Habitable planets
On the Pair-instability Supernova Origin of J1010+2358. The first (Population III) stars formed only out of H and He and were likely more massive than present-day stars. Massive Population III stars in the range 140─260 M ⊙ are predicted to end their lives as pair-instability supernovae (PISNe), enriching the environment with a unique abundance pattern, with high ratios of odd to even elements. Recently, the most promising candidate for a pure descendant of a zero-metallicity massive PISN (260 M ⊙) was discovered by the LAMOST survey, the star J1010+2358. However, key elements to verify the high PISN contribution, C and Al, were missing from the analysis. To rectify this, we obtained and analyzed a high-resolution Very Large Telescope/UVES spectrum, correcting for 3D and/or non-local thermodynamic equilibrium effects. Our measurements of both C and Al give much higher values (∼1 dex) than expected from a 260 M ⊙ PISN. Furthermore, we find significant discrepancies with the previous analysis and therefore a much less pronounced odd─even pattern. Our results show that J1010+2358 cannot be a pure descendant of a 260 M ⊙ PISN. Instead, we find that the best-fit model consists of a 13 M ⊙ Population II core-collapse supernova combined with a Population III supernova. Alternative, less favored solutions ( χ2/χbest2≍2.3 ) include a 50% contribution from a 260 M ⊙ PISN or a 40% contribution from a Population III Type Ia supernova. Ultimately, J1010+2358 is certainly a unique star giving insights into the earliest chemical enrichment; however, this star is not a pure PISN descendant. * Based on observations made with the Very Large Telescope (VLT) of the ESO at the La Silla Paranal Observatory under the program ID 112.26WJ.001

Keywords: Early universe, Population III stars, Stellar abundances, Galactic archaeology, Chemical abundances, Milky Way stellar halo
Filter Design for Estimation of Stellar Metallicity: Insights from Experiments with Gaia XP Spectra. We search for an optimal filter design for the estimation of stellar metallicity, based on synthetic photometry from Gaia XP spectra convolved with a series of filter-transmission curves defined by different central wavelengths and bandwidths. Unlike previous designs based solely on maximizing metallicity sensitivity, we find that the optimal solution provides a balance between the sensitivity and uncertainty of the spectra. With this optimal filter design, the best precision of metallicity estimates for relatively bright (G ∼ 11.5) stars is excellent, σ [Fe/H] = 0.034 dex for FGK dwarf stars, superior to that obtained utilizing custom sensitivity-optimized filters (e.g., SkyMapper v). By selecting hundreds of high-probability member stars of the open cluster M67, our analysis reveals that the intrinsic photometric-metallicity scatter of these cluster members is only 0.036 dex, consistent with this level of precision. Our results clearly demonstrate that the internal precision of photometric-metallicity estimates can be extremely high, even providing the opportunity to perform chemical tagging for very large numbers of field stars in the Milky Way. This experiment shows that it is crucial to take into account uncertainty alongside the sensitivity when designing filters for measuring the stellar metallicity and other parameters.

Keywords: Fundamental parameters of stars, Metallicity, Astronomy data analysis, Photometry
Friends Not Foes: Strong Correlation between Inner Super-Earths and Outer Gas Giants. The connection between outer gas giants and inner super-Earths reflects their formation and evolutionary histories. Past work exploring this link has suggested a tentative positive correlation between these two populations, but these studies have been limited by small sample sizes and in some cases sample biases. Here we take a new look at this connection with a sample of 184 super-Earth systems with publicly available radial velocity data and resolved outer gas giants. We calculate the frequency of outer gas giants (GG) in super-Earth (SE) systems, dividing our sample into metal-rich ([Fe/H] &gt; 0) and metal-poor ([Fe/H]≤0) hosts. We find P(GG∣SE, [Fe/H]&gt;0) =  28.0‑4.6+4.9%  and P(GG∣SE, [Fe/H]≤0) =  4.5‑1.9+2.6% . Comparing these conditional occurrence rates to field giant occurrence rates from Rosenthal et al. (2021), we show that there is a distinct positive correlation between inner super-Earths and outer gas giants for metal-rich host stars at the 2.7σ level, but this correlation disappears for metal-poor systems. We further find that, around metal-rich stars, the GG/SE correlation enhances slightly for systems with giants that are more distant (beyond 3 au), more eccentric (e &gt; 0.2), and/or in multi-gas giant systems. Such trends disappear around metal-poor stars with the exception of systems of multiple giants in which we observe a tentative anti-correlation. Our findings highlight the critical role metallicity (disk solid budget) plays in shaping the overall planetary architecture.

Keywords: Exoplanet astronomy, Exoplanet evolution, Exoplanet formation
Probing the Distinct Extinction Law of the Pillars of Creation in M16 with JWST. Investigating the extinction law in regions of high dust extinction, such as the Pillars of Creation within the M16 region, is crucial for understanding the densest parts of the interstellar medium (ISM). In this study, we utilize observations from the Near-Infrared Camera and the Mid-Infrared Instrument onboard the James Webb Space Telescope (JWST) to analyze the color-excess ratios E(F090W ‑ λ)/E(F090W ‑ F200W) across a wavelength range of 0.9–7.7 μm. Our method involves performing linear regression on color–color diagrams to derive these ratios. The enhanced detection capabilities of JWST data allow us to probe the distinct extinction law to the densest regions in M16 corresponding to an extinction depth up to A  V  ∼ 60 mag. Remarkably, the resultant color-excess ratio curve exhibits a flatter profile than predicted by typical dust extinction models with R  V  = 5.5 for dense ISM environments. Moreover, we observe that the mid-infrared extinction law diverges from the near-infrared power law, showing a tendency for the slope to flatten as the wavelength increases. These findings have significant implications for our understanding of the dust properties in dense interstellar environments.

Keywords: Interstellar extinction, Interstellar dust, Dense interstellar clouds, Reddening law
Pulsar Timing Noise from Brownian Motion of the Sun. Recently, pulsar timing arrays (PTAs) reported a signal at nanohertz frequencies consistent with a stochastic gravitational-wave background. Here, I show that the Brownian motion of the Sun as a result of its random gravitational interactions with the cluster of thousands of unmodeled main-belt asteroids of diameters ≲80 km, combined with small inaccuracies in the estimated masses of larger asteroids, introduces timing noise for pulsars, which is up to 20% of the reported signal at frequencies of ∼1 few years–1. The asteroid contribution needs to be modeled better in order to obtain accurate inferences from the PTA signal.

Keywords: Gravitational wave astronomy, Asteroid belt
Connecting Solar Wind Velocity Spikes Measured by Solar Orbiter and Coronal Brightenings Observed by SDO. The Parker Solar Probe's discovery that magnetic switchbacks and velocity spikes in the young solar wind are abundant has prompted intensive research into their origin(s) and formation mechanism(s) in the solar atmosphere. Recent studies, based on in situ measurements and numerical simulations, argue that velocity spikes are produced through interchange magnetic reconnection. Our work studies the relationship between interplanetary velocity spikes and coronal brightenings induced by changes in the photospheric magnetic field. Our analysis focuses on the characteristic periodicities of velocity spikes detected by the Proton Alpha Sensor on the Solar Orbiter during its fifth perihelion pass. Throughout the time period analyzed here, we estimate their origin along the boundary of a coronal hole. Around the boundary region, we identify periodic variations in coronal brightening activity observed by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. The spectral characteristics of the time series of in situ velocity spikes, remote coronal brightenings, and remote photospheric magnetic flux exhibit correspondence in their periodicities. Therefore, we suggest that the localized small-scale magnetic flux within coronal holes fuels a magnetic reconnection process that can be observed as slight brightness augmentations and outward fluctuations or jets. These dynamic elements may act as mediators, bonding magnetic reconnection with the genesis of velocity spikes and magnetic switchbacks.

Keywords: Supergranulation, Solar coronal transients, Solar wind, Interplanetary magnetic fields
Fits for the Convective Envelope Mass in Massive Stars. We explore the evolution of massive stars (&gt;8 M ⊙) with 1D models and present analytical fits to the masses and binding energies of the convective portions of their envelopes. These fits are given as functions of total mass, metallicity, and surface temperature (used as a proxy for evolutionary phase). They enable the application of the two-stage common envelope (CE) formalism in rapid binary population synthesis frameworks. We estimate that the degree of orbital hardening following CE ejection spans 6 orders of magnitude and is a very strong function of the accretor mass, and, to a lesser extent, donor evolutionary phase.

Keywords: Stellar evolution, Common envelope evolution, Common envelope binary stars