adsabs/SciX_UAT_keywords huggingface dataset:
A Framework for Obtaining Accurate Posteriors of Strong Gravitational Lensing Parameters with Flexible Priors and Implicit Likelihoods Using Density Estimation

We report the application of implicit likelihood inference to the prediction of the macroparameters of strong lensing systems with neural networks. This allows us to perform deep-learning analysis of lensing systems within a well-defined Bayesian statistical framework to explicitly impose desired priors on lensing variables, obtain accurate posteriors, and guarantee convergence to the optimal posterior in the limit of perfect performance. We train neural networks to perform a regression task to produce point estimates of lensing parameters. We then interpret these estimates as compressed statistics in our inference setup and model their likelihood function using mixture density networks. We compare our results with those of approximate Bayesian neural networks, discuss their significance, and point to future directions. Based on a test set of 100,000 strong lensing simulations, our amortized model produces accurate posteriors for any arbitrary confidence interval, with a maximum percentage deviation of 1.4% at the 21.8% confidence level, without the need for any added calibration procedure. In total, inferring 100,000 different posteriors takes a day on a single GPU, showing that the method scales well to the thousands of lenses expected to be discovered by upcoming sky surveys.

Keywords: strong gravitational lensing; convolutional neural networks; neural networks; markov chain monte carlo; posterior distribution; prior distribution; bayes' theorem; computational methods; gpu computing; confidence interval; gravitational lensing; gaussian mixture model
Spectroscopic Confirmation of Obscured AGN Populations from Unsupervised Machine Learning

We present the result of a spectroscopic campaign targeting active galactic nucleus (AGN) candidates selected using a novel unsupervised machine-learning (ML) algorithm trained on optical and mid-infrared photometry. AGN candidates are chosen without incorporating prior AGN selection criteria and are fainter, redder, and more numerous, ∼340 AGN deg‑2, than comparable photometric and spectroscopic samples. In this work, we obtain 178 rest-optical spectra from two candidate ML-identified AGN classes with the Hectospec spectrograph on the MMT Observatory. We find that our first ML-identified group is dominated by Type I AGNs (85%) with a <3% contamination rate from non-AGNs. Our second ML-identified group is mostly comprised of Type II AGNs (65%), with a moderate contamination rate of 15% primarily from star-forming galaxies. Our spectroscopic analyses suggest that the classes recover more obscured AGNs, confirming that ML techniques are effective at recovering large populations of AGNs at high levels of extinction. We demonstrate the efficacy of pairing existing WISE data with large-area and deep optical/near-infrared photometric surveys to select large populations of AGNs and recover obscured growth of supermassive black holes. This approach is well suited to upcoming photometric surveys, such as Euclid, Rubin, and Roman.

Keywords: active galactic nuclei; dimensionality reduction; galaxy spectroscopy
Hubble Space Telescope Search for Activity in High-perihelion Objects

Solar system objects with perihelia beyond the orbit of Jupiter (q > 5 au) are too cold for water ice to generate an appreciable coma via sublimation. Despite this, numerous high-perihelion objects (HPOs) including many comets and recently escaped Kuiper Belt objects (Centaurs) are observed to be active out at least to the orbit of Saturn (q ∼ 10 au). Peak equilibrium temperatures at 10 au (∼125 K), while far too low to sublimate water ice, are sufficient to sublimate supervolatiles such as CO and CO2 ice. Temperatures at 10 au are also high enough to trigger the rapid crystallization of exposed amorphous ice, thus constituting another possible driver of distant activity. While supervolatile ices can sublimate strongly (as ${r}_{{\rm{H}}}^{-2} ) to at least Kuiper Belt (30 au) distances, crystallization is an exponential function of temperature that cannot be sustained much beyond ∼10 au. The heliocentric dependence of the activity thus suggests an observational test. If activity in high-perihelion objects is triggered by crystallization, then no examples of activity should be found with perihelia of q ≫ 10 au. If, on the other hand, activity is due to free sublimation of exposed supervolatile ices, or another cause, then distant activity might be detected. We obtained sensitive, high-resolution Hubble Space Telescope observations of HPOs to search for activity beyond the crystallization zone. No examples of activity were detected in 53 objects with q > 15 au, consistent with the crystallization trigger hypothesis. However, sensitivity limits are such that we cannot reject the alternative hypothesis that mass loss is driven by the sublimation of supervolatile ices. We also searched for binary companions in our sample, finding none and setting an empirical 3σ limit to the binary fraction of <8%.

Keywords: comets; small solar system bodies; centaur group
Colors of Jupiter Trojan Dynamical Families as Measured by the Zwicky Transient Facility

We use data from the first two years of the public survey of the Zwicky Transient Facility to analyze colors of proposed Jupiter Trojan asteroid families. The well studied Eurybates cluster remains the only family with a significant number of color measurements, and we find that the average colors of this family are less red than typical Jupiter Trojans, in agreement with smaller studies. The limited number of objects detected in this and other surveys for the other families makes their colors continue to be uncertain.

Keywords: asteroid surfaces; jupiter trojans
Constraints on Evolutionary Timescales for M Dwarf Planets from Dynamical Stability Arguments

The diversity of dynamical conditions among exoplanets is now well established. Yet, the relevance of orbital dynamical timescales to biological evolutionary timescales is poorly understood. Given that even minor orbital changes may place significant pressure on any organisms living on a planet, dynamical sculpting has important implications for the putative evolution of life. In this manuscript, we employ a Monte Carlo framework to investigate how a range of exoplanetary dynamical sculpting timescales affects timescales for biological evolution. We proceed with minimal assumptions for how dynamical sculpting proceeds and the emergence and persistence of life. We focus our investigation on M dwarf stars, the most common exoplanetary hosts in the Milky Way. We assign dynamical statuses, dependent on stellar age, to a suite of planetary systems, varying the rate of dynamical disruption within limits that are consistent with present-day planet demographics. We then simulate the observed yield of planets according to the completeness of NASA's Kepler and TESS missions, and investigate the properties of these samples. With this simplified approach, we find that systems hosting multiple transiting planets ought to have, on average, shorter dynamically uninterrupted intervals than single-transiting systems. However, depending upon the rate of dynamical sculpting, planets orbiting older stars will exhibit the opposite trend. Even modest constraints on stellar age would help identify older stars for which this holds. The degree of these effects varies, dependent upon both the intrinsic dynamical demographics of exoplanets and whether we consider planets detected by NASA's Kepler or TESS missions.

Keywords: m dwarf stars; transits; habitable planets
Extreme Variability in a Long-duration Gamma-Ray Burst Associated with a Kilonova

The recent discovery of a kilonova from the long-duration gamma-ray burst (GRB) GRB 211211A challenges classification schemes based on temporal information alone. Gamma-ray properties of GRB 211211A reveal an extreme event, which stands out among both short and long GRBs. We find very short variations (few milliseconds) in the lightcurve of GRB 211211A and estimate ~1000 for the Lorentz factor of the outflow. We discuss the relevance of the short variations in identifying similar long GRBs resulting from compact mergers. Our findings indicate that in future gravitational-wave follow-up campaigns, some long-duration GRBs should be treated as possible strong gravitational-wave counterparts.

Keywords: gamma-ray bursts; gamma-rays
Confirmation of the Stellar Binary Microlensing Event, Macho 97-BLG-28

The high-magnification microlensing event MACHO-97-BLG-28 was previously determined to be a binary system composed of either two M dwarfs or an M dwarf and a brown dwarf. We present a revised light-curve model using additional data from the Mt. Stromlo 74″ telescope, model estimates of stellar limb darkening, and fitting of the blend separately for each telescope and passband. We find a lensing system with a larger mass ratio, q = 0.28 ± 0.01, and smaller projected separation, s = 0.61 ± 0.01, than those presented in the original study. We revise the estimate of the lens-source relative proper motion to μrel = 2.8 ± 0.5 mas yr-1, which indicates that 16.07 yr after the event maximum the lens and source should have separated by 46 ± 8 mas. We revise the radius of the source star using more recent reddening maps and angular diameter-color relations to R* = (10.3 ± 1.9) R⊙. K- and J-band adaptive optics images of the field taken at this epoch using the NIRC2 imager on the Keck telescope show that the source and lens are still blended, consistent with our light-curve model. With no statistically significant excess flux detection we constrain the mass, ${M}_{L}={0.24}_{-0.12}^{+0.28}\,{M}_{\odot }$ , and distance, DL = 7.0 ± 1.0 kpc, of the lensing system. This supports the interpretation of this event as a stellar binary in the Galactic bulge. This lens mass gives a companion mass of $M={0.07}_{-0.04}^{+0.08}\,{M}_{\odot }$ , close to the boundary between being a star and a brown dwarf.

Keywords: exoplanets; gravitational microlensing; proper motions
PROJECT-J: JWST Observations of HH46 IRS and Its Outflow. Overview and First Results

We present the first results of the JWST program PROJECT-J (PROtostellar JEts Cradle Tested with JWST), designed to study the Class I source HH46 IRS and its outflow through NIRSpec and MIRI spectroscopy (1.66–28 μm). The data provide line images (∼6.″6 in length with NIRSpec, and up to ∼20″ with MIRI) revealing unprecedented details within the jet, the molecular outflow, and the cavity. We detect, for the first time, the redshifted jet within ∼90 au from the source. Dozens of shock-excited forbidden lines are observed, including highly ionized species such as [Ne III] 15.5 μm, suggesting that the gas is excited by high velocity (>80 km s‑1) shocks in a relatively high-density medium. Images of H2 lines at different excitations outline a complex molecular flow, where a bright cavity, molecular shells, and a jet-driven bow shock interact with and are shaped by the ambient conditions. Additional NIRCam 2 μm images resolve the HH46 IRS ∼110 au binary system and suggest that the large asymmetries observed between the jet and the H2 wide-angle emission could be due to two separate outflows being driven by the two sources. The spectra of the unresolved binary show deep ice bands and plenty of gaseous lines in absorption, likely originating in a cold envelope or disk. In conclusion, JWST has unraveled for the first time the origin of the HH46 IRS complex outflow demonstrating its capability to investigate embedded regions around young stars, which remain elusive even at near-IR wavelengths.

Keywords: young stellar objects; protostars; stellar jets; infrared spectroscopy; protoplanetary disks
Plasma Emission Induced by Electron Cyclotron Maser Instability in Solar Plasmas with a Large Ratio of Plasma Frequency to Gyrofrequency

In plasmas with a large ratio of plasma frequency to gyrofrequency (ωpe/Ωce), energetic electrons characterized by \partial f/\partial {V}_{\perp }> 0 can excite electron cyclotron maser instability (ECMI), generating waves of upper hybrid (UH), Z, and W modes. It has been presumed that these ECMI waves can somehow convert to escaping X-O modes as fundamental (F) or harmonic (H) plasma emission. Here we perform a fully kinetic, electromagnetic particle-in-cell simulation to investigate the proposed radiation process. ECMI is driven by energetic electrons with a Dory-Guest-Harris distribution representative of a double-sided loss cone, and ωpe/Ωce is set to be 10. We find that the electrostatic UH mode is the fastest-growing mode. Around the time when its energy starts to decline, the W mode grows to be dominant. During this stage, we observe significant F and H plasma emission. The F emission is in the O mode with a bandwidth around 0.1-0.2 Ωce, and the H emission is contributed by both X and O modes with a narrower bandwidth. We suggest that the O-F emission is caused by coalescence of almost counterpropagating Z and W modes, while the H emission arises from coalescence of an almost counterpropagating UH mode at relatively large wave number. Thus the plasma emission investigated here is induced by a combination of wave growth due to ECMI and further nonlinear wave-coupling processes. The result is relevant to understanding solar radio bursts as well as other astronomical radio sources that are excited by energetic electrons trapped within certain magnetic structures.

Keywords: solar corona; solar activity; radio bursts; solar coronal radio emission; plasma astrophysics
JADES: Resolving the Stellar Component and Filamentary Overdense Environment of Hubble Space Telescope (HST)-dark Submillimeter Galaxy HDF850.1 at z = 5.18

HDF850.1 is the brightest submillimeter galaxy (SMG) in the Hubble Deep Field. It is known as a heavily dust-obscured star-forming galaxy embedded in an overdense environment at z = 5.18. With nine-band NIRCam images at 0.8-5.0 μm obtained through the JWST Advanced Deep Extragalactic Survey, we detect and resolve the rest-frame UV-optical counterpart of HDF850.1, which splits into two components because of heavy dust obscuration in the center. The southern component leaks UV and Hα photons, bringing the galaxy ~100 times above the empirical relation between infrared excess and UV continuum slope (IRX-β UV). The northern component is higher in dust attenuation and thus fainter in UV and Hα surface brightness. We construct a spatially resolved dust-attenuation map from the NIRCam images, well matched with the dust continuum emission obtained through millimeter interferometry. The whole system hosts a stellar mass of 1010.8±0.1 M ⊙ and star formation rate (SFR) of 102.8±0.2 M ⊙ yr-1, placing the galaxy at the massive end of the star-forming main sequence at this epoch. We further confirm that HDF850.1 resides in a complex overdense environment at z = 5.17-5.30, which hosts another luminous SMG at z = 5.30 (GN10). The filamentary structures of the overdensity are characterized by 109 Hα-emitting galaxies confirmed through NIRCam slitless spectroscopy at 3.9-5 μm, of which only eight were known before the JWST observations. Given the existence of a similar galaxy overdensity in the GOODS-S field, our results suggest that 50% ± 20% of the cosmic star formation at z = 5.1-5.5 occur in protocluster environments.

Keywords: high-redshift galaxies; luminous infrared galaxies; ultraluminous infrared galaxies; galaxy evolution; james webb space telescope
The Subterahertz Solar Cycle: Polar and Equatorial Radii Derived from SST and ALMA

At subterahertz frequencies—i.e., millimeter and submillimeter wavelengths—there is a gap in measurements of the solar radius, as well as other parameters of the solar atmosphere. As the observational wavelength changes, the radius varies because the altitude of the dominant electromagnetic radiation is produced at different heights in the solar atmosphere. Moreover, radius variations throughout long time series are indicative of changes in the solar atmosphere that may be related to the solar cycle. Therefore, the solar radius is an important parameter for the calibration of solar atmospheric models enabling a better understanding of the atmospheric structure. In this work, we use data from the Solar Submillimeter-wave Telescope (SST) and the Atacama Large Millimeter/submillimeter Array (ALMA) at frequencies of 100, 212, 230, and 405 GHz to measure the equatorial and polar radii of the Sun. The radii measured with extensive data from the SST agree with the radius-versus-frequency trend present in the literature. The radii derived from ALMA maps at 230 GHz also agree with the radius-versus-frequency trend, whereas the 100 GHz radii are slightly above the values reported by other authors. In addition, we analyze the equatorial and polar radius behavior over the years by determining the correlation coefficient between solar activity and subterahertz radius time series at 212 and 405 GHz (SST). The variations of the SST-derived radii over 13 yr are correlated to the solar activity when considering equatorial regions of the solar atmosphere and anticorrelated when considering polar regions. The ALMA-derived radius time series for 100 and 230 GHz show very similar behaviors with those of SST.

Keywords: solar atmosphere; solar radio emission; center to limb observations; time series analysis
Enhancing Pulsar Candidate Identification with Self-tuning Pseudolabeling Semisupervised Learning

In the field of astronomy, machine-learning technologies are becoming increasingly crucial for identifying radio pulsars. However, the process of acquiring labeled data, which is both time-consuming and potentially biased, poses a significant limitation to current methodologies. In response to these challenges, this study proposes and validates a self-tuning pseudolabeling semisupervised learning approach. This approach synthesizes a vast unlabeled data set with a considerably smaller set of labeled data, markedly enhancing classifier performance and effectuating a transition from traditional fully supervised learning methods to more efficient radio pulsar detection strategies. Our experimental outcomes demonstrate that even with a training set comprised of only 100 labeled pulsar candidates, this method can attain a recall rate of 92.35% and an F1 score of 93.89%. When the number of labeled examples is increased to 800, we observe a further improvement in performance, with the recall rate rising to 97.50% and the F1 score reaching 97.16%. The utility of the semisupervised learning approach is evident even with minimal labeled data, which is a common scenario in the search for pulsars, including in environments like globular clusters. What stands out is the method's capacity to detect pulsar candidates effectively with only a limited number of labeled examples. This emphasizes the robust potential of our approach to facilitate early-stage pulsar surveys and highlights its capability to yield substantial results even when labeled data are in short supply.

Keywords: pulsars; convolutional neural networks; radio pulsars; astronomy data analysis; astronomy data modeling; astronomical object identification
Spatial Extent of Molecular Gas, Dust, and Stars in Massive Galaxies at z ∼ 2.2-2.5 Determined with ALMA and JWST

We present the results of 0.″6-resolution observations of CO J = 3 - 2 line emission in 10 massive star-forming galaxies at z ~ 2.2-2.5 with the Atacama Large Millimeter/submillimeter Array (ALMA). We compare the spatial extent of molecular gas with those of dust and stars, traced by the 870 and 4.4 μm continuum emissions, respectively. The average effective radius of the CO emission is 1.75 ± 0.34 kpc, which is about 60% larger than that of the 870 μm emission and is comparable with that of the 4.4 μm emission. Utilizing the best-fit parametric models, we derive the radial gradients of the specific star formation rate (sSFR), gas depletion timescale, and gas-mass fraction within the observed galaxies. We find a more intense star formation activity with a higher sSFR and a shorter depletion timescale in the inner region than in the outer region. The central starburst may be the primary process for massive galaxies to build up a core. Furthermore, the gas-mass fraction is high, independent of the galactocentric radius in the observed galaxies, suggesting that the galaxies have not begun to quench star formation. Given the shorter gas depletion timescale in the center compared to the outer region, quenching is expected to occur in the center first and then propagate outward. We may be witnessing the observed galaxies in the formation phase of a core prior to the forthcoming phase of star formation propagating outward.

Keywords: starburst galaxies; high-redshift galaxies
Hubble Space Telescope Imaging Reveals That SN 2015bh Is Much Fainter than Its Progenitor

We present Hubble Space Telescope (HST) imaging of the site of SN 2015bh in the nearby spiral galaxy NGC 2770 taken between 2017 and 2019, nearly four years after the peak of the explosion. In 2017-2018, the transient fades steadily in optical filters before declining more slowly to F814W = -7.1 mag in 2019, ≈4 mag below the level of its eruptive luminous blue variable (LBV) progenitor observed with HST in 2008-2009. The source fades at a constant color of F555W - F814W = 0.4 mag until 2018, similar to SN 2009ip and consistent with a spectrum dominated by interaction of the ejecta with circumstellar material (CSM). A deep optical spectrum obtained in 2021 lacks signatures of ongoing interaction (L Hα ≲ 1038 erg s-1 for broadened emission ≲2000 km s-1), but indicates the presence of a nearby H II region (≲300 pc). The color evolution of the fading source makes it unlikely that emission from a scattered-light echo or binary OB companion of the progenitor contributes significantly to the flattening of the late-time light curve. The remaining emission in 2019 may plausibly be attributed an evolved/inflated companion or an unresolved (≲3 pc), young stellar cluster. Importantly, the color evolution of SN 2015bh rules out scenarios in which the surviving progenitor is obscured by nascent dust and does not clearly indicate a transition to a hotter, optically faint state. The simplest explanation is that the massive progenitor did not survive. SN 2015bh likely represents a remarkable example of the terminal explosion of a massive star preceded by decades of end-stage eruptive variability.

Keywords: supernovae; luminous blue variable stars; massive stars; stellar mass loss; evolved stars