Sazuna/UAT_keywords huggingface dataset:
A Late-time Radio Flare Following a Possible Transition in Accretion State in the Tidal Disruption Event AT 2019azh. We report here radio follow-up observations of the optical tidal disruption event (TDE) AT 2019azh. Previously reported X-ray observations of this TDE showed variability at early times and a dramatic increase in luminosity, by a factor of ~10, about 8 months after optical discovery. The X-ray emission is mainly dominated by intermediate hard-soft X-rays and is exceptionally soft around the X-ray peak, which is L  X  ~ 1043 erg s-1. The high cadence 15.5 GHz observations reported here show an early rise in radio emission followed by an approximately constant light curve, and a late-time flare. This flare starts roughly at the time of the observed X-ray peak luminosity and reaches its peak about 110 days after the peak in the X-ray, and a year after optical discovery. The radio flare peaks at ν L  ν  ~ 1038 erg s-1, a factor of two higher than the emission preceding the flare. In light of the late-time radio and X-ray flares, and the X-ray spectral evolution, we speculate a possible transition in the accretion state of this TDE, similar to the observed behavior in black hole X-ray binaries. We compare the radio properties of AT 2019azh to other known TDEs, and focus on the similarities to the late-time radio flare of the TDE ASASSN-15oi.

Keywords: Black holes, High energy astrophysics, Tidal disruption, Transient sources, Time domain astronomy, Radio transient sources
Using LSST Microlensing to Constrain Dark Compact Objects in Spherical and Disk Configurations. The Legacy Survey of Space and Time (LSST) with the Vera Rubin Observatory will provide strong microlensing constraints on dark compact objects (DCOs) in our Galaxy. However, most current forecasts limit their analysis to Primordial Black Holes (PBH). It is unclear how well LSST microlensing will be able to constrain alternative models of DCOs with different Galactic spatial profile distributions at a subdominant DM fraction. In this work, we investigate how well LSST microlensing will constrain spherical or disk-like Galactic spatial distributions of DCOs, taking into account extended observing times, baryonic microlensing background, and sky distribution of LSST sources. These extensions represent significant improvements over existing microlensing forecasts in terms of both accuracy and versatility. We demonstrate this power by deriving new LSST sensitivity projections for DCOs in spherical and disk-like distributions. We forecast that LSST will be able to constrain one-solar-mass PBHs to have a DM fraction under 4.1 × 10-4. One-solar-mass objects in a dark disk distribution with the same dimensions as the Galactic disk will be constrained below 3.1 × 10-4, while those with m = 105 M ⊙ will be constrained to below 3.4 × 10-5. We find that compressed dark disks can be constrained up to a factor of ~10 better than ones with identical dimensions to the baryonic disk. We also find that dark disks become less tightly constrained when they are tilted with respect to our own disk. This forecasting software is a versatile tool, capable of constraining any model of DCOs in the Milky Way with microlensing, and is made publicly available.

Keywords: Milky Way dark matter halo, Dark matter distribution, Sky surveys, Dark matter, Navarro-Frenk-White profile, Compact objects, Particle physics, Gravitational microlensing, Microlensing event rate, Particle astrophysics
Disks and Outflows in the Intermediate-mass Star-forming Region NGC 2071 IR. We present Atacama Large Millimeter Array band 6/7 (1.3 mm/0.87 mm) and Very Large Array Ka-band (9 mm) observations toward NGC 2071 IR, an intermediate-mass star-forming region. We characterize the continuum and associated molecular line emission toward the most luminous protostars, i.e., IRS1 and IRS3, on ~100 au (0.″2) scales. IRS1 is partly resolved in the millimeter and centimeter continuum, which shows a potential disk. IRS3 has a well-resolved disk appearance in the millimeter continuum and is further resolved into a close binary system separated by ~40 au at 9 mm. Both sources exhibit clear velocity gradients across their disk major axes in multiple spectral lines including C18O, H2CO, SO, SO2, and complex organic molecules like CH3OH, 13CH3OH, and CH3OCHO. We use an analytic method to fit the Keplerian rotation of the disks and give constraints on physical parameters with a Markov Chain Monte Carlo routine. The IRS3 binary system is estimated to have a total mass of 1.4-1.5 M ☉. IRS1 has a central mass of 3-5 M ☉ based on both kinematic modeling and its spectral energy distribution, assuming that it is dominated by a single protostar. For both IRS1 and IRS3, the inferred ejection directions from different tracers, including radio jet, water maser, molecular outflow, and H2 emission, are not always consistent, and for IRS1 these can be misaligned by ~50°. IRS3 is better explained by a single precessing jet. A similar mechanism may be present in IRS1 as well but an unresolved multiple system in IRS1 is also possible.

Keywords: Protostars, Stellar jets, Star formation, Protoplanetary disks
Effects of CO-dark Gas on Measurements of Molecular Cloud Stability and the Size-Linewidth Relationship. Stars form within molecular clouds, so characterizing the physical states of molecular clouds is key to understanding the process of star formation. Cloud structure and stability are frequently assessed using metrics including the virial parameter and Larson scaling relationships between cloud radius, velocity dispersion, and surface density. Departures from the typical Galactic relationships between these quantities have been observed in low-metallicity environments. The amount of H2 gas in cloud envelopes without corresponding CO emission is expected to be high under these conditions; therefore, this CO-dark gas could plausibly be responsible for the observed variations in cloud properties. We derive simple corrections that can be applied to empirical clump properties (mass, radius, velocity dispersion, surface density, and virial parameter) to account for CO-dark gas in clumps following power-law and Plummer mass density profiles. We find that CO-dark gas is not likely to be the cause of departures from Larson's relationships in low-metallicity regions, but that virial parameters may be systematically overestimated. We demonstrate that correcting for CO-dark gas is critical for accurately comparing the dynamical state and evolution of molecular clouds across diverse environments.

Keywords: Molecular clouds, Interstellar medium
The Time Domain Spectroscopic Survey: Changing-look Quasar Candidates from Multi-epoch Spectroscopy in SDSS-IV. Active galactic nuclei (AGN) can vary significantly in their rest-frame optical/UV continuum emission, and with strong associated changes in broad line emission, on much shorter timescales than predicted by standard models of accretion disks around supermassive black holes. Most such changing-look or changing-state AGN-and at higher luminosities, changing-look quasars (CLQs)-have been found via spectroscopic follow-up of known quasars showing strong photometric variability. The Time Domain Spectroscopic Survey of the Sloan Digital Sky Survey IV (SDSS-IV) includes repeat spectroscopy of large numbers of previously known quasars, many selected irrespective of photometric variability, and with spectral epochs separated by months to decades. Our visual examination of these repeat spectra for strong broad line variability yielded 61 newly discovered CLQ candidates. We quantitatively compare spectral epochs to measure changes in continuum and Hβ broad line emission, finding 19 CLQs, of which 15 are newly recognized. The parent sample includes only broad line quasars, so our study tends to find objects that have dimmed, i.e., turn-off CLQs. However, we nevertheless find four turn-on CLQs that meet our criteria, albeit with broad lines in both dim and bright states. We study the response of Hβ and Mg II emission lines to continuum changes. The Eddington ratios of CLQs are low, and/or their Hβ broad line width is large relative to the overall quasar population. Repeat quasar spectroscopy in the upcoming SDSS-V black hole Mapper program will reveal significant numbers of CLQs, enhancing our understanding of the frequency and duty cycle of such strong variability, and the physics and dynamics of the phenomenon.

Keywords: Accretion, Variable radiation sources, Quasars, Active galactic nuclei, Catalogs
Characteristics of Multi-scale Current Sheets in the Solar Wind at 1 au Associated with Magnetic Reconnection and the Case for a Heliospheric Current Sheet Avalanche. Wind spacecraft measurements are analyzed to obtain a current sheet (CS) normal width d cs distribution of 3374 confirmed magnetic reconnection exhausts in the ecliptic plane of the solar wind at 1 au. The d cs distribution displays a nearly exponential decay from a peak at d cs = 25 d  i  to a median at d cs = 85 d  i  and a 95th percentile at d cs = 905 d  i  with a maximum exhaust width at d cs = 8077 d  i . A magnetic field θ-rotation angle distribution increases linearly from a relatively few high-shear events toward a broad peak at 35° &lt; θ &lt; 65°. The azimuthal ϕ angles of the CS normal directions of 430 thick d cs ≥ 500 d  i  exhausts are consistent with a dominant Parker-spiral magnetic field and a CS normal along the ortho-Parker direction. The CS normal orientations of 370 kinetic-scale d cs &lt; 25 d  i  exhausts are isotropic in contrast, and likely associated with Alfvénic solar wind turbulence. We propose that the alignment of exhaust normal directions from narrow d cs ~ 15-25 d  i  widths to well beyond d cs ~ 500 d  i  with an ortho-Parker azimuthal direction of a large-scale heliospheric current sheet (HCS) is a consequence of CS bifurcation and turbulence within the HCS exhaust that may trigger reconnection of the adjacent pair of bifurcated CSs. The proposed HCS-avalanche scenario suggests that the underlying large-scale parent HCS closer to the Sun evolves with heliocentric distance to fracture into many, more or less aligned, secondary CSs due to reconnection. A few wide exhaust-associated HCS-like CSs could represent a population of HCSs that failed to reconnect as frequently between the Sun and 1 au as other HCSs.

Keywords: Interplanetary turbulence, Solar wind, Solar magnetic reconnection, Heliosphere
COMAP Early Science. I. Overview. The CO Mapping Array Project (COMAP) aims to use line-intensity mapping of carbon monoxide (CO) to trace the distribution and global properties of galaxies over cosmic time, back to the Epoch of Reionization (EoR). To validate the technologies and techniques needed for this goal, a Pathfinder instrument has been constructed and fielded. Sensitive to CO(1-0) emission from z = 2.4-3.4 and a fainter contribution from CO(2-1) at z = 6-8, the Pathfinder is surveying 12 deg2 in a 5 yr observing campaign to detect the CO signal from z ~ 3. Using data from the first 13 months of observing, we estimate P CO(k) = -2.7 ± 1.7 × 104 μK2 Mpc3 on scales k = 0.051 -0.62 Mpc-1, the first direct three-dimensional constraint on the clustering component of the CO(1-0) power spectrum. Based on these observations alone, we obtain a constraint on the amplitude of the clustering component (the squared mean CO line temperature bias product) of ${\left\langle {Tb}\right\rangle }^{2}\lt 49$ μK2, nearly an order-of-magnitude improvement on the previous best measurement. These constraints allow us to rule out two models from the literature. We forecast a detection of the power spectrum after 5 yr with signal-to-noise ratio (S/N) 9-17. Cross-correlation with an overlapping galaxy survey will yield a detection of the CO-galaxy power spectrum with S/N of 19. We are also conducting a 30 GHz survey of the Galactic plane and present a preliminary map. Looking to the future of COMAP, we examine the prospects for future phases of the experiment to detect and characterize the CO signal from the EoR.

Keywords: Molecular gas, Cosmological evolution, High-redshift galaxy clusters, Astronomical instrumentation, CO line emission, Radio astronomy
COMAP Early Science. II. Pathfinder Instrument. Line intensity mapping (LIM) is a new technique for tracing the global properties of galaxies over cosmic time. Detection of the very faint signals from redshifted carbon monoxide (CO), a tracer of star formation, pushes the limits of what is feasible with a total-power instrument. The CO Mapping Project Pathfinder is a first-generation instrument aiming to prove the concept and develop the technology for future experiments, as well as delivering early science products. With 19 receiver channels in a hexagonal focal plane arrangement on a 10.4 m antenna and an instantaneous 26-34 GHz frequency range with 2 MHz resolution, it is ideally suited to measuring CO (J = 1-0) from z ~ 3. In this paper we discuss strategies for designing and building the Pathfinder and the challenges that were encountered. The design of the instrument prioritized LIM requirements over those of ancillary science. After a couple of years of operation, the instrument is well understood, and the first year of data is already yielding useful science results. Experience with this Pathfinder will guide the design of the next generations of experiments.

Keywords: Galaxy clusters, Molecular gas, Galaxy formation, High-redshift galaxy clusters, Radio telescopes, Astronomical instrumentation, Cassegrain telescopes, Radio astronomy
COMAP Early Science. III. CO Data Processing. We describe the first-season CO Mapping Array Project (COMAP) analysis pipeline that converts raw detector readouts to calibrated sky maps. This pipeline implements four main steps: gain calibration, filtering, data selection, and mapmaking. Absolute gain calibration relies on a combination of instrumental and astrophysical sources, while relative gain calibration exploits real-time total-power variations. High-efficiency filtering is achieved through spectroscopic common-mode rejection within and across receivers, resulting in nearly uncorrelated white noise within single-frequency channels. Consequently, near-optimal but biased maps are produced by binning the filtered time stream into pixelized maps; the corresponding signal bias transfer function is estimated through simulations. Data selection is performed automatically through a series of goodness-of-fit statistics, including χ 2 and multiscale correlation tests. Applying this pipeline to the first-season COMAP data, we produce a data set with very low levels of correlated noise. We find that one of our two scanning strategies (the Lissajous type) is sensitive to residual instrumental systematics. As a result, we no longer use this type of scan and exclude data taken this way from our Season 1 power spectrum estimates. We perform a careful analysis of our data processing and observing efficiencies and take account of planned improvements to estimate our future performance. Power spectrum results derived from the first-season COMAP maps are presented and discussed in companion papers.

Keywords: Molecular gas, Cosmological evolution, CO line emission, Radio astronomy, High-redshift galaxies
COMAP Early Science. IV. Power Spectrum Methodology and Results. We present the power spectrum methodology used for the first-season COMAP analysis, and assess the quality of the current data set. The main results are derived through the Feed-Feed Pseudo-Cross-Spectrum (FPXS) method, which is a robust estimator with respect to both noise modeling errors and experimental systematics. We use effective transfer functions to take into account the effects of instrumental beam smoothing and various filter operations applied during the low-level data processing. The power spectra estimated in this way have allowed us to identify a systematic error associated with one of our two scanning strategies, believed to be due to residual ground or atmospheric contamination. We omit these data from our analysis and no longer use this scanning technique for observations. We present the power spectra from our first season of observing, and demonstrate that the uncertainties are integrating as expected for uncorrelated noise, with any residual systematics suppressed to a level below the noise. Using the FPXS method, and combining data on scales k = 0.051-0.62 Mpc-1, we estimate P CO(k) = -2. 7 ± 1.7 × 104 μK2 Mpc3, the first direct 3D constraint on the clustering component of the CO(1-0) power spectrum in the literature.

Keywords: Molecular gas, Cosmological evolution, CO line emission, Radio astronomy, High-redshift galaxies
COMAP Early Science. V. Constraints and Forecasts at z   3. We present the current state of models for the z ~ 3 carbon monoxide (CO) line intensity signal targeted by the CO Mapping Array Project (COMAP) Pathfinder in the context of its early science results. Our fiducial model, relating dark matter halo properties to CO luminosities, informs parameter priors with empirical models of the galaxy-halo connection and previous CO (1-0) observations. The Pathfinder early science data spanning wavenumbers k = 0.051-0.62 Mpc-1 represent the first direct 3D constraint on the clustering component of the CO (1-0) power spectrum. Our 95% upper limit on the redshift-space clustering amplitude A clust ≲ 70 μK2 greatly improves on the indirect upper limit of 420 μK2 reported from the CO Power Spectrum Survey (COPSS) measurement at k ~ 1 Mpc-1. The COMAP limit excludes a subset of models from previous literature and constrains interpretation of the COPSS results, demonstrating the complementary nature of COMAP and interferometric CO surveys. Using line bias expectations from our priors, we also constrain the squared mean line intensity-bias product, ${\left\langle {Tb}\right\rangle }_{2}$ ≲ 50 μK2, and the cosmic molecular gas density, ρ H2 &lt; 2.5 × 108 M ⊙ Mpc-3 (95% upper limits). Based on early instrument performance and our current CO signal estimates, we forecast that the 5 yr Pathfinder campaign will detect the CO power spectrum with overall signal-to-noise ratio of 9-17. Between then and now, we also expect to detect the CO-galaxy cross-spectrum using overlapping galaxy survey data, enabling enhanced inferences of cosmic star formation and galaxy evolution history.

Keywords: Molecular gas, Cosmological evolution, CO line emission, Radio astronomy, High-redshift galaxies
COMAP Early Science. VI. A First Look at the COMAP Galactic Plane Survey. We present early results from the CO Mapping Array Project (COMAP) Galactic Plane Survey conducted between 2019 June and 2021 April, spanning 20° &lt; ℓ &lt; 40° in Galactic longitude and ∣b∣ &lt; 1.°5 in Galactic latitude with an angular resolution of 4.'5. We present initial results from the first part of the survey, including the diffuse emission and spectral energy distributions of H II regions and supernova remnants (SNRs). Using low- and high-frequency surveys to constrain free-free and thermal dust emission contributions, we find evidence of excess flux density at 30 GHz in six regions, which we interpret as anomalous microwave emission. Furthermore we model ultracompact H II contributions using data from the 5 GHz CORNISH catalog and reject these as the cause of the 30 GHz excess. Six known SNRs are detected at 30 GHz, and we measure spectral indices consistent with the literature or show evidence of steepening. The flux density of the SNR W44 at 30 GHz is consistent with a power-law extrapolation from lower frequencies with no indication of spectral steepening in contrast with recent results from the Sardinia Radio Telescope. We also extract five hydrogen radio recombination lines (RRLs) to map the warm ionized gas, which can be used to estimate electron temperatures or to constrain continuum free-free emission. The full COMAP Galactic Plane Survey, to be released in 2023/2024, will span ℓ ~ 20°-220° and will be the first large-scale radio continuum and RRL survey at 30 GHz with 4.'5 resolution.

Keywords: Surveys, Supernova remnants, Interstellar medium, Radio continuum emission, H II regions, Milky Way Galaxy
COMAP Early Science. VII. Prospects for CO Intensity Mapping at Reionization. We introduce COMAP-EoR, the next generation of the Carbon Monoxide Mapping Array Project aimed at extending CO intensity mapping to the Epoch of Reionization. COMAP-EoR supplements the existing 30 GHz COMAP Pathfinder with two additional 30 GHz instruments and a new 16 GHz receiver. This combination of frequencies will be able to simultaneously map CO(1-0) and CO(2-1) at reionization redshifts (z ~ 5-8) in addition to providing a significant boost to the z ~ 3 sensitivity of the Pathfinder. We examine a set of existing models of the EoR CO signal, and find power spectra spanning several orders of magnitude, highlighting our extreme ignorance about this period of cosmic history and the value of the COMAP-EoR measurement. We carry out the most detailed forecast to date of an intensity mapping cross correlation, and find that five out of the six models we consider yield signal to noise ratios (S/Ns) ≳ 20 for COMAP-EoR, with the brightest reaching a S/N above 400. We show that, for these models, COMAP-EoR can make a detailed measurement of the cosmic molecular gas history from z ~ 2-8, as well as probe the population of faint, star-forming galaxies predicted by these models to be undetectable by traditional surveys. We show that, for the single model that does not predict numerous faint emitters, a COMAP-EoR-type measurement is required to rule out their existence. We briefly explore prospects for a third-generation Expanded Reionization Array (COMAP-ERA) capable of detecting the faintest models and characterizing the brightest signals in extreme detail.

Keywords: Molecular gas, Cosmological evolution, Radio astronomy, CO line emission, Reionization, High-redshift galaxies
The Splashback Mass Function in the Presence of Massive Neutrinos. We present a complementary methodology to constrain the total neutrino mass, ∑m  ν , based on the diffusion coefficient of the splashback mass function of dark matter halos. Analyzing the snapshot data from the Massive Neutrino Simulations, we numerically obtain the number densities of distinct halos identified via the SPARTA code as a function of their splashback masses at various redshifts for two different cases of ∑m  ν  = 0.0 and 0.1 eV. Then, we fit the numerical results to the recently developed analytic formula characterized by the diffusion coefficient that quantifies the degree of ambiguity in the identification of the splashback boundaries. Our analysis confirms that the analytic formula works excellently even in the presence of neutrinos and that the decrement of its diffusion coefficient with redshift is well described by a linear fit, B(z - z  c ), in the redshift range of 0.2 ≤ z ≤ 2. It turns out that the massive neutrino case yields a significantly lower value of B and a substantially higher value of z  c  than the massless neutrino case, which indicates that the higher the masses that neutrinos have, the more severely the splashback boundaries become disturbed by the surroundings. Given our result, we conclude that the total neutrino mass can in principle be constrained by measuring how rapidly the diffusion coefficient of the splashback mass function diminishes with redshifts at z ≥ 0.2. We also discuss the anomalous behavior of the diffusion coefficient found at lower redshifts for both of the ∑m  ν  cases, and ascribe it to the fundamental limitation of the SPARTA code at z ≤ 0.13.

Keywords: Large-scale structure of the universe