Sazuna/UAT_keywords huggingface dataset:
Redshift Prediction with Images for Cosmology Using a Bayesian Convolutional Neural Network with Conformal Predictions. In the emerging era of big data astrophysics, large-scale extragalactic surveys will soon provide high-quality imaging for billions of celestial objects to answer major questions in astrophysics such as the nature of dark matter and dark energy. Precision cosmology with surveys requires accurate photometric redshift (photo-z) estimation with well-constrained uncertainties as inputs for weak lensing models to measure cosmological parameters. Machine learning methods have shown promise in optimizing the information gained from galaxy images in photo-z estimation; however, many of these methods are limited in their ability to estimate accurate uncertainties. In this work, we present one of the first applications of Bayesian convolutional neural networks (BCNNs) for photo-z estimation and uncertainties. In addition, we use conformal mapping to calibrate the photo-z uncertainties to achieve good statistical coverage. We use the public GalaxiesML data set of ∼300k galaxies from the Hyper Suprime-Cam survey containing five-band photometric images and known spectroscopic redshifts from 0 &lt; z &lt; 4. We find that the performance is much improved when using images compared to photometry, with the BCNN achieving 0.098 rms error, a standard outlier rate of 3.9%, a 3σ outlier rate of 4.5%, and a bias of 0.0007. The performance drops significantly beyond z &gt; 1.5 due to the relative lack of training data beyond those redshifts. This investigation demonstrates the power of using images directly and we advocate that future photo-z analysis of large-scale surveys include galaxy images.

Keywords: Cosmology, Galaxy distances, Bayesian statistics, Redshifted, Convolutional neural networks
The Origins of Narrow Spectra of Fast Radio Bursts. Observations find that some fast radio bursts (FRBs) have extremely narrowband spectra, i.e., Δν/ν 0 ≪ 1. We show that, when the angular size of the emission region is larger than the Doppler beaming angle, the observed spectral width (Δν/ν 0) exceeds 0.58 due to the high-latitude effects for a source outside the magnetosphere, even when the spectrum in the source's comoving frame is monochromatic. The angular size of the source for magnetospheric models of FRBs can be smaller than the Doppler beaming angle, in which case this geometric effect does not influence the observed bandwidth. We discuss various propagation effects to determine if any could transform a broad-spectrum radio pulse into a narrow spectrum signal at the observer's location. We find that plasma lensing and scintillation can result in a narrow bandwidth in the observed spectrum. However, the likelihood of these phenomena being responsible for the narrow observed spectra with Δν/ν 0 &lt; 0.58 in the fairly large observed sample of FRBs is exceedingly small.

Keywords: Non-thermal radiation sources
Very Extended Ionized Gas Discovered around NGC 1068 with the Circumgalactic Hα Spectrograph. We have performed wide-field, ultra-low-surface-brightness Hα emission-line mapping around NGC 1068 with the newly commissioned Circumgalactic Hα Spectrograph. NGC 1068 is notable for its active galactic nucleus, which globally ionizes gas in the disk and halo. Line-emitting diffuse ionized gas is distributed throughout the galactic disk and large-scale ionized filaments are found well beyond the disk, aligned with the cone angle of the central jet. We report the discovery of a new ribbon of ionized gas around NGC 1068 beyond even the known outer filamentary structure, located 20 kpc from the galaxy. The Hα surface brightness of this ribbon is on the order of the bright telluric lines, ranging from 4 to 16 R, with fainter regions on the order of the sky background continuum. Unlike previous extended emission, the ribbon is not as well aligned with the current axis of the central jet. It is not associated with any galactic structure or known tidal features in the halo of NGC 1068, though it may originate from a larger distribution of unmapped neutral atomic or molecular gas in the halo. The morphology of the ribbon emission in Hα is correlated with extended UV emission around NGC 1068. Hα-to-UV flux ratios in the ribbon are comparable to extended emission-line ratios in the halos of NGC 5128, NGC 253, and M82. The Hα excess in the ribbon gas suggests ionization by slow shocks or a mixture of in situ star formation and photoionization and collisional ionization processes.

Keywords: Active galaxies, Seyfert galaxies, Spectroscopy, Circumgalactic medium, H II regions
Structured Jet Model for Multiwavelength Observations of the Jetted Tidal Disruption Event AT 2022cmc. AT 2022cmc is a recently documented tidal disruption event that exhibits a luminous jet, accompanied by fast-declining X-ray and long-lasting radio and millimeter emission. Motivated by the distinct spectral and temporal signatures between the X-ray and radio observations, we propose a multizone model involving relativistic jets with different Lorentz factors. We systematically study the evolution of faster and slower jets in an external density profile, considering the continuous energy injection rate associated with time-dependent accretion rates before and after the mass fallback time. We investigate time-dependent multiwavelength emission from both the forward shock (FS) and reverse shock (RS) regions of the fast and slow jets, in a self-consistent manner. Our analysis demonstrates that the energy injection rate can significantly impact the jet evolution and subsequently influence the lightcurves. We find that the X-ray spectra and lightcurves could be described by electron synchrotron emission from the RS of the faster jet, in which the late-time X-ray upper limits, extending to 400 days after the disruption, could be interpreted as a jet break. Meanwhile, the radio observations can be interpreted as a result of synchrotron emission from the FS region of the slower jet. We also discuss prospects for testing the model with current and future observations.

Keywords: Tidal disruption, Relativistic jets, Transient sources, Radiative processes
Thermodynamic Evolution of Plumes. Plumes are considered to play an important role in the origin of the solar wind. However, an understanding of their thermodynamic evolution is not complete. Here, we perform a detailed study of a plume inside a coronal hole throughout its lifetime, using the observations from the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager. We find that the plume's formation is preceded by frequent occurrences of small-scale jets and jetlets at its base, leading to the gradual development of plume haze. The plume rapidly developed within the first 6 hr into its well-known morphology. Light curves from all extreme ultraviolet channels exhibit a similar profile, suggesting its multithermal nature and intensity modulation over its lifespan. Moreover, the photospheric magnetic field dynamics at the plume's base are highly correlated with its light curve in 171 Å. We calculate outflow velocities, observed prominently in the 171 Å passband and mildly in the 193 and 211 Å passbands, with median speeds lower in higher temperature bands but occasionally comparable to the respective sound speeds. When data are averaged over larger spatial scales, the plume appears isothermal along its length, with constant temperature throughout its lifetime. However, an analysis of the differential emission measure at full resolution reveals the presence of higher-temperature plasma, indicating internal temperature structures within the plume. These results provide new insights into the formation, dynamics, and thermal properties of coronal plumes, placing tighter constraints on models to understand their thermodynamic evolution and potential role in the solar wind.

Keywords: Solar coronal holes, Solar coronal plumes
Searching for Bumps in the Cosmological Road: Do Type Ia Supernovae with Early Excesses Have Biased Hubble Residuals?. Flux excesses in the early-time light curves of Type Ia supernovae (SNe Ia) are predicted by multiple theoretical models and have been observed in a number of nearby SNe Ia over the last decade. However, the astrophysical processes that cause these excesses may affect their use as standardizable candles for cosmological parameter measurements. We perform a systematic search for early-time excesses in SNe Ia observed by the Zwicky Transient Facility (ZTF) to study whether SNe Ia with these excesses yield systematically different Hubble residuals. We analyze two compilations of SN Ia light curves from ZTF's first year of operations: 127 high-cadence light curves from Y. Yao et al. and 305 light curves from the ZTF cosmology data release of S. Dhawan et al. We detect significant early-time excesses for 17 SNe Ia in these samples and find that the excesses have a median g ‑ r color of 0.10 ± 0.11 mag; we do not find a clear preference for blue excesses as predicted by several models. Using the SALT3 model, we measure Hubble residuals for these two samples, finding that excess-having SNe Ia may have lower Hubble residuals (HR) after correcting for shape, color, and host-galaxy mass, at ∼2–3σ significance; our baseline result is ΔHR = ‑0.056 ± 0.026 mag (2.2σ). We compare the host-galaxy masses of excess-having and no-excess SNe Ia and find they are consistent, though at marginal significance excess-having SNe Ia may prefer lower-mass hosts. Additional discoveries of early excess SNe Ia will be a powerful way to understand potential biases in SN Ia cosmology and probe the physics of SN Ia progenitors.

Keywords: Cosmology, Light curves, Type Ia supernovae, Dark energy
Pre-peak Emission in Tidal Disruption Events. The rising part of a tidal disruption event light curve provides unique insight into early emission and the onset of accretion. Various mechanisms are proposed to explain the pre-peak emission, including shocks from debris interaction and reprocessing of disk emission. We study the pre-peak emission and its influence on the gas circularization by a series of gray radiation hydrodynamic simulations with varying black hole mass. We find that, given a super-Eddington fallback rate of  10ṀEdd , the stream–stream collision can occur multiple times and drive strong outflows of up to  9ṀEdd . By dispersing gas to ≳100r  s , the outflow can delay gas circularization and leads to sub-Eddington accretion rates during the first few stream–stream collisions. The stream–stream collision shock and circularization shock can sustain a luminosity of ∼1044 erg s‑1 for days. The luminosity is generally sub-Eddington and shows a weak correlation with accretion rate at early times. The outflow is optically thick, yielding a reprocessing layer with a size of ∼1014 cm and photospheric temperature of ∼4 × 104 K.

Keywords: Accretion, Hydrodynamical simulations, Tidal disruption, Compact radiation sources
Spectral Calculations of 3D Radiation Magnetohydrodynamic Simulations of Super-Eddington Accretion onto a Stellar-mass Black Hole. We use the Athena++ Monte Carlo (MC) radiation transfer module to postprocess simulation snapshots from nonrelativistic Athena++ radiation magnetohydrodynamic (RMHD) simulations. These simulations were run using a gray (frequency-integrated) approach but were also restarted and ran with a multigroup approach that accounts for Compton scattering with a Kompaneets operator. These simulations produced moderately super-Eddington accretion rates onto a 6.62 M ⊙ black hole. Since we only achieve inflow equilibrium out to 20─25 gravitational radii, we focus on the hard X-ray emission. We provide a comparison between the MC and RMHD simulations, showing that the treatment of Compton scattering in the gray RMHD simulations underestimates the gas temperature in the funnel regions above and below the accretion disk. In contrast, the restarted multigroup snapshots provide a treatment for the radiation field that is more consistent with the MC calculations, and result in postprocessed spectra with harder X-ray emission compared to their gray snapshot counterparts. We characterize these MC postprocessed spectra using commonly employed phenomenological spectral fitting models. We also attempt to fit our MC spectra directly to observations of the ultraluminous X-ray source (ULX) NGC 1313 X-1, finding best-fit values that are competitive to phenomenological model fits, indicating that first principle models of super-Eddington accretion may adequately explain the observed hard X-ray spectra in some ULX sources.

Keywords: X-ray astronomy, Astronomy data modeling, Schwarzschild black holes, Stellar mass black holes, Ultraluminous x-ray sources, Radiative transfer simulations, Astrophysical black holes, Magnetohydrodynamical simulations
Deciphering the Kinematic Substructure of Local Dark Matter with LAMOST K Giants. Numerical simulations indicate that correlations exist between the velocity distributions of stars and dark matter (DM). We study the local DM velocity distribution based on these correlations. We select K giants from LAMOST DR8 cross-matched with Gaia DR3, which have robust measurements of velocity and metallicity, and separate them into the disk, halo substructure, and isotropic halo components in the chemodynamical space utilizing the Gaussian mixture model. The substructure component is highly radially anisotropic and possibly related to the Gaia–Enceladus–Sausage (GES) merger event, while the isotropic halo component is accreted from the earliest mergers following the Maxwell–Boltzmann distribution (standard halo model [SHM]). We find that the GES-like substructure contributes ∼85% of the local nondisk stars in the solar neighborhood, which is nearly invariant when applying different volume cuts or additional angular momentum constraints. Utilizing the metallicity–stellar mass relation and the stellar mass–halo mass relation, we find that  ∼25‑15+24%  of local DM is in the kinematic substructure. Combined with the stellar distributions of nondisk components, we modify the heliocentric velocity distribution of local DM. It shifts to a lower speed with a sharper peak compared to the SHM and updates the detection limits of DM direct detection experiments. We discuss extensively the degeneracies present in the GMM fitting and propose that more kinematic and chemical information such as α abundance could help to break the degeneracy in the future. Our work confirms that the local DM velocity distribution deviates significantly from the SHM and needs to be properly accounted for in the DM detection experiments.

Keywords: Milky Way stellar halo, Milky Way dynamics, Milky Way Galaxy
Data-driven MHD Simulation of the Formation of a Magnetic Flux Rope and an Inclined Solar Eruption. Solar energetic events are caused by the release of magnetic energy accumulated in the solar atmosphere. To understand their initiating physical mechanisms, the dynamics of the coronal magnetic fields must be studied. Unfortunately, the dominant mechanisms are still unclear due to a lack of direct measurements. Numerical simulations based on magnetohydrodynamics (MHD) can reproduce the dynamical evolution of solar coronal magnetic field, providing a useful tool to explore flare initiation. Data-driven MHD simulations, in which the time-series observational data of the photospheric magnetic field is used as the simulation boundary condition, can explore different mechanisms. To investigate the accumulation of free magnetic energy through a solar eruption, we simulated the first of several large flares in NOAA active region 11283. We used a data-driven model that was governed by zero-beta MHD, focusing on the free magnetic energy accumulation prior to the M5.3 flare (2011 September 6 at 01:59 UT). We reproduced the flare-associated eruption following the formation of twisted magnetic fields, or a magnetic flux rope (MFR), formed by photospheric motions at its footpoints. We found that the eruption was first triggered by the growth of the torus instability. The erupting MFR caused magnetic reconnections with neighboring magnetic field lines located along the direction of the eruption. Using the simulation results and an axial-radial decay index centered on the MFR, we find a natural explanation for the inclination of the eruption and a possible approach to predict the direction of solar eruptive events.

Keywords: Solar magnetic flux emergence, Solar flares, Solar physics, Solar coronal mass ejections, Solar corona, Magnetohydrodynamical simulations
Superphot+: Real-time Fitting and Classification of Supernova Light Curves. Photometric classifications of supernova (SN) light curves have become necessary to utilize the full potential of large samples of observations obtained from wide-field photometric surveys, such as the Zwicky Transient Facility (ZTF) and the Vera C. Rubin Observatory. Here, we present a photometric classifier for SN light curves that does not rely on redshift information and still maintains comparable accuracy to redshift-dependent classifiers. Our new package, Superphot+, uses a parametric model to extract meaningful features from multiband SN light curves. We train a gradient-boosted machine with fit parameters from 6061 ZTF SNe that pass data quality cuts and are spectroscopically classified as one of five classes: SN Ia, SN II, SN Ib/c, SN IIn, and SLSN-I. Without redshift information, our classifier yields a class-averaged F 1-score of 0.61 ± 0.02 and a total accuracy of 0.83 ± 0.01. Including redshift information improves these metrics to 0.71 ± 0.02 and 0.88 ± 0.01, respectively. We assign new class probabilities to 3558 ZTF transients that show SN-like characteristics (based on the ALeRCE Broker light-curve and stamp classifiers) but lack spectroscopic classifications. Finally, we compare our predicted SN labels with those generated by the ALeRCE light-curve classifier, finding that the two classifiers agree on photometric labels for 82% ± 2% of light curves with spectroscopic labels and 72% ± 0% of light curves without spectroscopic labels. Superphot+ is currently classifying ZTF SNe in real time via the ANTARES Broker, and is designed for simple adaptation to six-band Rubin light curves in the future.

Keywords: Nested sampling, Light curve classification , Transient detection, Supernovae
Contemporaneous X-Ray Observations of 30 Bright Radio Bursts from the Prolific Fast Radio Burst Source FRB 20220912A. We present an extensive contemporaneous X-ray and radio campaign performed on the repeating fast radio burst (FRB) source FRB 20220912A for 8 weeks immediately following the source's detection by CHIME/FRB. This includes X-ray data from XMM-Newton, NICER, and Swift, and radio detections of FRB 20220912A from CHIME/Pulsar and Effelsberg. We detect no significant X-ray emission at the time of 30 radio bursts with upper limits on a 0.5─10.0 keV X-ray fluence of (1.5─14.5) × 10−10 erg cm−2 (99.7% credible interval, unabsorbed) on a timescale of 100 ms. Translated into a fluence ratio η x/r = F X-ray/F radio, this corresponds to η x/r &lt; 7 × 106. For persistent emission from the location of FRB 20220912A, we derive a 99.7% 0.5─10.0 keV isotropic flux limit of 8.8 × 10−15 erg cm−2 s−1 (unabsorbed) or an isotropic luminosity limit of 1.4 × 1041 erg s−1 at a distance of 362.4 Mpc. We derive a hierarchical extension to the standard Bayesian treatment of low-count and background-contaminated X-ray data, which allows the robust combination of multiple observations. This methodology allows us to place the best (lowest) 99.7% credible interval upper limit on an FRB η x/r to date, η x/r &lt; 2 × 106, assuming that all 30 detected radio bursts are associated with X-ray bursts with the same fluence ratio. If we instead adopt an X-ray spectrum similar to the X-ray burst observed contemporaneously with FRB-like emission from the Galactic magnetar SGR 1935+2154 detected on 2020 April 28, we derive a 99.7% credible interval upper limit on η x/r of 8 × 105, which is only 3 times the observed value of η x/r for SGR 1935+2154.

Keywords: Neutron stars, High energy astrophysics, Magnetars, X-ray bursts, Radio transient sources
A Multiwavelength Portrait of the 3C 220.3 Lensed System. The 3C 220.3 system is a rare case of a foreground narrow-line radio galaxy ("galaxy A," z  A  = 0.6850) lensing a background submillimeter galaxy (z SMG = 2.221). New spectra from MMT/Binospec confirm that the companion galaxy ("galaxy B") is part of the lensing system with z  B  = 0.6835. New three-color Hubble Space Telescope (HST) data reveal a full Einstein ring and allow a more precise lens model. The new HST images also reveal extended emission around galaxy A, and the spectra show extended [O II] emission with irregular morphology and complex velocity structure. All indications are that the two lensing galaxies are a gravitationally interacting pair. Strong [O II] emission from both galaxies A and B suggests current star formation, which could be a consequence of the interaction. This would indicate a younger stellar population than previously assumed and imply smaller stellar masses for the same luminosity. The improved lens model and expanded spectral energy distributions have enabled better stellar mass estimates for the foreground galaxies. The resulting dark matter fractions are ∼0.8, which are higher than previously calculated. Deeper Chandra imaging shows extended X-ray emission but no evidence for an X-ray point source associated with either galaxy. The detection of X-rays from the radio lobes of 3C 220.3 allows an estimate of ∼3 nT for the magnetic fields in the lobes, a factor of ∼3 below the equipartition fields, as is typical for radio galaxies.

Keywords: Strong gravitational lensing, Active galaxies, Radio lobes, Radio galaxies, Infrared galaxies, Dark matter
Anomaly Detection and Approximate Similarity Searches of Transients in Real-time Data Streams. We present Lightcurve Anomaly Identification and Similarity Search (LAISS), an automated pipeline to detect anomalous astrophysical transients in real-time data streams. We deploy our anomaly detection model on the nightly Zwicky Transient Facility (ZTF) Alert Stream via the ANTARES broker, identifying a manageable ∼1─5 candidates per night for expert vetting and coordinating follow-up observations. Our method leverages statistical light-curve and contextual host galaxy features within a random forest classifier, tagging transients of rare classes (spectroscopic anomalies), of uncommon host galaxy environments (contextual anomalies), and of peculiar or interaction-powered phenomena (behavioral anomalies). Moreover, we demonstrate the power of a low-latency (∼ms) approximate similarity search method to find transient analogs with similar light-curve evolution and host galaxy environments. We use analogs for data-driven discovery, characterization, (re)classification, and imputation in retrospective and real-time searches. To date, we have identified ∼50 previously known and previously missed rare transients from real-time and retrospective searches, including but not limited to superluminous supernovae (SLSNe), tidal disruption events, SNe IIn, SNe IIb, SNe I-CSM, SNe Ia-91bg-like, SNe Ib, SNe Ic, SNe Ic-BL, and M31 novae. Lastly, we report the discovery of 325 total transients, all observed between 2018 and 2021 and absent from public catalogs (∼1% of all ZTF Astronomical Transient reports to the Transient Name Server through 2021). These methods enable a systematic approach to finding the "needle in the haystack" in large-volume data streams. Because of its integration with the ANTARES broker, LAISS is built to detect exciting transients in Rubin data.

Keywords: Classification, Astrostatistics techniques, Light curves, Time domain astronomy, Transient detection, Supernovae, Random Forests, Astronomical methods, Time series analysis