Sazuna/UAT_keywords huggingface dataset:
Powerful Radio-loud Quasars Are Triggered by Galaxy Mergers in the Cosmic Bright Ages. While supermassive black holes are ubiquitous features of galactic nuclei, only a small minority are observed during episodes of luminous accretion. The physical mechanism(s) driving the onset of fueling and ignition in these active galactic nuclei (AGN) are still largely unknown for many galaxies and AGN-selection criteria. Attention has focused on AGN triggering by means of major galaxy mergers gravitationally funneling gas toward the galactic center, with evidence both for and against this scenario. However, several recent studies have found that radio-loud AGN overwhelmingly reside in ongoing or recent major galaxy mergers. In this study, we test the hypothesis that major galaxy mergers are important triggers for radio-loud AGN activity in powerful quasars during cosmic noon (1 ≲ z ≲ 2). To this end, we compare Hubble Space Telescope WFC3/IR observations of the z &gt; 1 3CR radio-loud broad-lined quasars to three matched radio-quiet quasar control samples. We find strong evidence for major-merger activity in nearly all radio-loud AGN, in contrast to the much lower merger fraction in the radio-quiet AGN. These results suggest major galaxy mergers are key ingredients in launching powerful radio jets. Given many of our radio-loud quasars are blue, our results present a possible challenge to the "blowout" paradigm of galaxy evolution models in which blue quasars are the quiescent end result following a period of red quasar feedback initiated by a galaxy merger. Finally, we find a tight correlation between black hole mass and host galaxy luminosity for these different high-redshift AGN samples that is inconsistent with those observed for local elliptical galaxies.

Keywords: Radio loud quasars, Radio jets, Active galactic nuclei, Galaxy mergers
CLASS Angular Power Spectra and Map-component Analysis for 40 GHz Observations through 2022. Measurement of the largest angular scale (ℓ &lt; 30) features of the cosmic microwave background (CMB) polarization is a powerful way to constrain the optical depth to reionization and search for the signature of inflation through the detection of primordial B-modes. We present an analysis of maps covering 73.6% of the sky made from the 40 GHz channel of the Cosmology Large Angular Scale Surveyor (CLASS) from 2016 August to 2022 May. Taking advantage of the measurement stability enabled by front-end polarization modulation and excellent conditions from the Atacama Desert, we show this channel achieves higher sensitivity than the analogous frequencies from satellite measurements in the range 10 &lt; ℓ &lt; 100. Simulations show the CLASS linear (circular) polarization maps have a white noise level of $125(130)\,\mu {\rm{K}}\,\mathrm{arcmin}$ . We measure the Galaxy-masked EE and BB spectra of diffuse synchrotron radiation and compare to space-based measurements at similar frequencies. In combination with external data, we expand measurements of the spatial variations of the synchrotron spectral energy density (SED) to include new sky regions and measure the diffuse SED in the harmonic domain. We place a new upper limit on a background of circular polarization in the range 5 &lt; ℓ &lt; 125 with the first bin showing D  ℓ  &lt; 0.023 $\mu {{\rm{K}}}_{\mathrm{CMB}}^{2}$ at 95% confidence. These results establish a new standard for recovery of the largest-scale CMB polarization from the ground and signal exciting possibilities when the higher sensitivity and higher-frequency CLASS channels are included in the analysis.

Keywords: Early universe, Cosmic microwave background radiation, Observational cosmology, Astronomy data analysis, Polarimeters
Modeling of Radio Supernovae: Including the Effects of Inhomogeneities and Radiative Cooling. The presence of inhomogeneities in a spatially unresolved source is often hard to establish. This limits the accuracy with which the source properties can be determined. It is shown how observed features not expected for a homogeneous model can be used to infer the properties of the inhomogeneities in radio supernovae. Furthermore, the observed consequences of radiative cooling can be seriously affected by inhomogeneities. It is shown that the deduced source properties are very sensitive to the observed value of the cooling frequency; even a lower limit is often useful to constrain its characteristics. It is argued that the main synchrotron emission region in SN 2003L has a small volume filling factor, possibly as low as a few percent. On the contrary, deviations from homogeneity are substantially smaller in SN 2002ap. The observed properties of Type Ib/c radio supernovae in general indicate the volume filling factor to remain rather constant with time for individual sources, but those peaking later at radio frequencies have lower filling factors. The conditions in the main synchrotron component in both SN 2003L and SN 2002ap are consistent with equipartition of energy between relativistic electrons and magnetic fields.

Keywords: Non-thermal radiation sources, Radiative processes, Radio continuum emission, Shocks, Magnetic fields, Supernovae
JWST Mid-infrared Spectroscopy Resolves Gas, Dust, and Ice in Young Stellar Objects in the Large Magellanic Cloud. In this work, we present spectra of 11 young stellar objects (YSOs) taken with the Mid-Infrared Instrument / Medium Resolution Spectroscopy (MRS) instrument on board the James Webb Space Telescope (JWST). The YSOs are located in the N79 region of the Large Magellanic Cloud (LMC), an active star-forming region with hundreds of Spitzer- and Herschel-identified YSOs and host to super star cluster (SSC) candidate H72.97-69.39. The three giant molecular clouds in N79 (East, West, and South) have varying star formation rates and stellar populations. MRS follow-up observations of four Spitzer-identified YSOs in N79 East, West, and South have revealed that what seemed to be a single, massive YSO is actually a cluster of YSOs. We discuss the emission and absorption lines of six YSOs that have complete or almost-complete spectral coverage from 4.9–27.9 μm. YSO Y3, located in N79 East, is the youngest source in this study and likely to be less than 10,000 yr old, as inferred from the prominent CH4, NH3, CH3OH, CH3OCHO, and CO2 ice absorption features. The most luminous source is the central ionizing YSO of SSC H72.97-69.39, Y4, which has dozens of fine-structure and H2 emission lines. Unlike the other YSOs in this work, Y4 has no polyaromatic hydrocarbon emission lines, due to the intense ionizing radiation destroying these large carbon-chain molecules. The mass accretion rates based on the H I (7-6) line luminosities of YSOs Y1, Y2, Y4, and Y9 range between 1.22 × 10‑4–1.89 × 10‑2 M ⊙ yr‑1. For the first time in the mid-infrared, we are able to resolve individual high-mass protostars forming in small clusters in an extragalactic environment like the LMC.

Keywords: Young stellar objects, Large Magellanic Cloud
Chemical Cartography of the Sagittarius Stream with Gaia. The stellar stream connected to the Sagittarius (Sgr) dwarf galaxy is the most massive tidal stream that has been mapped in the Galaxy, and is the dominant contributor to the outer stellar halo of the Milky Way (MW). We present metallicity maps of the Sgr stream, using 34,240 red giant branch stars with inferred metallicities from Gaia BP/RP spectra. This sample is larger than previous samples of Sgr stream members with chemical abundances by an order of magnitude. We measure metallicity gradients with respect to Sgr stream coordinates (Λ, B), and highlight the gradient in metallicity with respect to stream latitude coordinate B, which has not been observed before. Including the core, we find ∇[M/H] = ‑2.48 ± 0.08 × 10‑2 dex deg‑1 above the stream track (B &gt; B 0, where B 0 = 1.5° is the latitude of the Sgr remnant) and ∇[M/H] = ‑2.02 ± 0.08 × 10‑2 dex deg‑1 below the stream track (B &lt; B 0). By painting metallicity gradients onto a tailored N-body simulation of the Sgr stream, we find that the observed metallicities in the stream are consistent with an initial radial metallicity gradient in the Sgr dwarf galaxy of ∼‑0.1 to ‑0.2 dex kpc‑1, well within the range of observed metallicity gradients in Local Group dwarf galaxies. Our results provide novel observational constraints for the internal structure of the dwarf galaxy progenitor of the Sgr stream. Leveraging new large data sets in conjunction with tailored simulations, we can connect the present-day properties of disrupted dwarfs in the MW to their initial conditions.

Keywords: Stellar streams, Milky Way stellar halo, Chemical abundances, Galaxy chemical evolution
Coronagraphic Data Post-processing Using Projections on Instrumental Modes. Directly observing exoplanets with coronagraphs is impeded by the presence of speckles from aberrations in the optical path, which can be mitigated in hardware with wave front control, as well as in post-processing. This work explores using an instrument model in post-processing to separate astrophysical signals from residual aberrations in coronagraphic data. The effect of wave front error (WFE) on the coronagraphic intensity consists of a linear contribution and a quadratic contribution. When either of the terms is much larger than the other, the instrument response can be approximated by a transfer matrix mapping WFE to detector plane intensity. From this transfer matrix, a useful projection onto instrumental modes that removes the dominant error modes can be derived. We apply this approach to synthetically generated Roman Space Telescope hybrid Lyot coronagraph data to extract "robust observables," which can be used instead of raw data for applications such as detection testing. The projection improves planet flux ratio detection limits by about 28% in the linear regime and by over a factor of 2 in the quadratic regime, illustrating that robust observables can increase sensitivity to astrophysical signals and improve the scientific yield from coronagraphic data. While this approach does not require additional information such as observations of reference stars or modulations of a deformable mirror, it can and should be combined with these other techniques, acting as a model-informed prior in an overall post-processing strategy.

Keywords: Exoplanet astronomy, Coronagraphic imaging, Exoplanet detection methods, Direct imaging
MIDIS: JWST NIRCam and MIRI Unveil the Stellar Population Properties of Lyα Emitters and Lyman-break Galaxies at z ≃ 3─7. We study the stellar population properties of 182 spectroscopically confirmed (MUSE/VLT) Lyα emitters (LAEs) and 450 photometrically selected Lyman-break galaxies (LBGs) at z = 2.8─6.7 in the Hubble Extreme Deep Field. Leveraging the combined power of Hubble Space Telescope and JWST NIRCam and MIRI observations, we analyze their rest-frame UV-through-near-IR spectral energy distributions, with MIRI playing a crucial role in robustly assessing the LAEs' stellar masses and ages. Our LAEs are low-mass objects $({{\rm{log}}}_{10}({M}_{\star }/{M}_{\odot })\simeq 7.5)$ with little or no dust extinction (E(B − V) ≃ 0.1) and a blue UV continuum slope (β ≃ −2.2). While 75% of our LAEs are young (&lt;100 Myr), the remaining 25% have significantly older stellar populations (≥100 Myr). These old LAEs are statistically more massive, less extinct, and have lower specific star formation rate than young LAEs. Besides, they populate the plane of M ⋆ versus star formation rate along the main sequence of star-forming galaxies, while young LAEs populate the starburst region. The comparison between the LAEs' properties and those of a stellar-mass-matched sample of LBGs shows no statistical difference between these objects, except for the LBGs' redder UV continuum slope and marginally larger E(B − V) values. Interestingly, 48% of the LBGs have ages &lt;10 Myr and are classified as starbursts, but lack detectable Lyα emission. This is likely due to H I resonant scattering and/or dust-selective extinction. Overall, we find that JWST observations are crucial in determining the properties of LAEs and shedding light on their comparison with LBGs.

Keywords: Lyman-alpha galaxies, Infrared telescopes, Lyman-break galaxies, Galaxy evolution
Explaining the GWSkyNet-Multi Machine Learning Classifier Predictions for Gravitational-wave Events. GWSkyNet-Multi is a machine learning model developed for the classification of candidate gravitational-wave events detected by the LIGO and Virgo observatories. The model uses limited information released in the low-latency Open Public Alerts to produce prediction scores indicating whether an event is a merger of two black holes (BHs), a merger involving a neutron star (NS), or a non-astrophysical glitch. This facilitates time-sensitive decisions about whether to perform electromagnetic follow-up of candidate events during LIGO-Virgo-KAGRA (LVK) observing runs. However, it is not well understood how the model is leveraging the limited information available to make its predictions. As a deep learning neural network, the inner workings of the model can be difficult to interpret, impacting our trust in its validity and robustness. We tackle this issue by systematically perturbing the model and its inputs to explain what underlying features and correlations it has learned for distinguishing the sources. We show that the localization area of the 2D sky maps and the computed coherence versus incoherence Bayes factors are used as strong predictors for distinguishing between real events and glitches. The estimated distance to the source is further used to discriminate between binary BH mergers and mergers involving NSs. We leverage these findings to show that events misclassified by GWSkyNet-Multi in LVK's third observing run have distinct sky areas, coherence factors, and distance values that influence the predictions and explain these misclassifications. The results help identify the model's limitations and inform potential avenues for further optimization.

Keywords: Gravitational wave astronomy, Convolutional neural networks, Gravitational wave sources
Active Galactic Nuclei in a Mid-infrared Selected Galaxy Sample at z &gt; 0.13: [Ne V]λ3426 Line Emission as a Benchmark. We present a 24 μm-selected spectroscopic sample z &gt; 0.13 (median &lt;z&gt; = 0.41) in the Lockman Hole field, consisting of 4035 spectra. Our aim is to identify active galactic nuclei (AGNs) and determine their fraction in this mid-infrared-selected sample. In this work, we use the [Ne V]λ3426 emission line to spectroscopically identify AGNs. Combined with broad-line Type I AGNs selected in our previous study, our sample consists of 887 (∼22%) spectroscopically confirmed AGNs. We perform a stacking analysis on the remaining spectra and find that in various mid-infrared (MIR) wedge-selected AGN candidates, the stacked spectra still show significant [Ne V]λ3426 emission. In contrast, no clear [Ne V]λ3426 signal is detected in non-AGN candidates falling outside the wedges. Assuming a range of AGN MIR spectral energy distribution (SED) slope of ‑0.3 &lt;α &lt; 0.7, and an average star-forming relation derived from 65 star-forming templates, we develop a robust method to separate the AGN and star-forming contributions to the MIR SEDs using the rest-frame L 12/L 1.6 versus L 4.5/L 1.6 diagram. We separate the objects into bins of L 12 and find that the AGN fraction increases with increasing L 12. We also find that the stacked [Ne V]λ3426 strength scales with L 12. The pure AGN luminosity at 12 μm exhibits a positive correlation with the star formation rates, indicating possible coevolution and common gas supply between the AGNs and their host galaxies. Varying population properties across the redshift range explored contribute to the observed correlation.

Keywords: AGN host galaxies, Galaxy spectroscopy, Active galactic nuclei, Infrared galaxies
LISA Galactic Binaries with Astrometry from Gaia DR3. Galactic compact binaries with orbital periods shorter than a few hours emit detectable gravitational waves (GWs) at low frequencies. Their GW signals can be detected with the future Laser Interferometer Space Antenna (LISA). Crucially, they may be useful in the early months of the mission operation in helping to validate LISA's performance in comparison to prelaunch expectations. We present an updated list of 55 candidate LISA-detectable binaries with measured properties, for which we derive distances based on Gaia Data Release 3 astrometry. Based on the known properties from electromagnetic observations, we predict the LISA detectability after 1, 3, 6, and 48 months using Bayesian analysis methods. We distinguish between verification and detectable binaries as being detectable after 3 and 48 months, respectively. We find 18 verification binaries and 22 detectable sources, which triples the number of known LISA binaries over the last few years. These include detached double white dwarfs, AM CVn binaries, one ultracompact X-ray binary, and two hot subdwarf binaries. We find that across this sample the GW amplitude is expected to be measured to ≈10% on average, while the inclination is expected to be determined with ≈15° precision. For detectable binaries, these average errors increase to ≈50% and ≈40°, respectively.

Keywords: Gravitational wave sources, White dwarf stars, Compact binary stars, Semi-detached binary stars
Exploring Neutral Hydrogen in Radio MOlecular Hydrogen Emission Galaxies (MOHEGs) and Prospects with the SKA. Empirical studies of cold gas content are essential for comprehending the star formation activities and evolution in galaxies. However, it is not straightforward to understand these processes because they depend on various physical properties of the interstellar medium. Massive Faranoff–Riley I/II type radio galaxies rich in molecular hydrogen with lower star formation activities are known as radio molecular hydrogen emission galaxies (MOHEGs). We present a study of neutral hydrogen-gas-associated radio MOHEGs at redshifts &lt;0.2 probed via the H I 21 cm absorption line. Neutral hydrogen is detected in 70% of these galaxies, which are located at a distance of 8–120 kpc from the neighboring galaxies. These galaxies show a scarcity of H I gas as compared to merging galaxies at similar redshifts. We found no strong correlation between N(H I), NH, and the galaxy properties, regardless of whether the H I is assumed to be cold or warm, indicating that the atomic gas probably plays no important role in star formation. The relation between the total hydrogen gas surface density and the star formation surface density deviates from the standard Kennicutt–Schmidt law. Our study highlights the importance of H I studies and offers insights into the role of atomic and molecular hydrogen gas in explaining the properties of these galaxies. In the upcoming H I 21 cm absorption surveys with next-generation radio telescopes such as the Square Kilometre Array and pathfinder instruments, it may be possible to provide better constraints for these correlations.

Keywords: Star formation, Fanaroff-Riley radio galaxies
Do Faculae Affect Autocorrelation Rotation Periods in Sun-like Stars?. Rotational periods derived from autocorrelation function (ACF) techniques on stars photometrically similar to the Sun in Kepler data have proven difficult to reliably determine. We investigate various instrumental and astrophysical factors affecting the accuracy of these measurements, including the effects of observational windows and noise, stellar activity and inclination, spectral passbands, and the separate normalization of contiguous segments. We validate that the flux variations due to faculae are very periodic, but starspots are the dominant source of bolometric and visible differential variability in Sun-like stars on rotational timescales. We quantify how much stronger the relative contribution of faculae would have to be to render Sun-like light curves periodic enough to reliably measure with autocorrelation methods. We also quantify how long starspot lifetimes need to be to render pure spot light curves periodic enough. In general, longer observational windows yield more accurate ACF measurements, even when faculae are not present. Due to the enhancement of the relative contribution of faculae, observing stars with intermediate inclinations, during activity minima, and/or through bluer passbands has the effect of strengthening the periodicity of the light curve. We search for other manifestations of faculae in broadband photometry of Sun-like stars and conclude that without absolute flux measurements or restriction to shorter-wavelength passbands, differential light curves are uninformative about faculae.

Keywords: Starspots, Solar rotation, Light curves, Sunspots, Solar faculae, Stellar rotation
The ALMA View of Positive Black Hole Feedback in the Dwarf Galaxy Henize 2─10. Henize 2─10 is a dwarf starburst galaxy hosting a ∼106 M ☉ black hole (BH) that is driving an ionized outflow and triggering star formation within the central ∼100 pc of the galaxy. Here, we present Atacama Large Millimeter/submillimeter Array continuum observations from 99 to 340 GHz, as well as spectral line observations of the molecules CO (1─0, 3─2), HCN (1─0, 3─2), and HCO+ (1─0, 3─2), with a focus on the BH and its vicinity. Incorporating centimeter-wave radio measurements from the literature, we show that the spectral energy distribution of the BH is dominated by synchrotron emission from 1.4 to 340 GHz, with a spectral index of α ≈ − 0.5. We analyze the spectral line data and identify an elongated molecular gas structure around the BH with a velocity distinct from the surrounding regions. The physical extent of this molecular gas structure is ≈130 pc × 30 pc and the molecular gas mass is ∼106 M ☉. Despite an abundance of molecular gas in this general region, the position of the BH is significantly offset from the peak intensity, which may explain why the BH is radiating at a very low Eddington ratio. Our analysis of the spatially resolved line ratio between CO J = 3─2 and J = 1─0 implies that the CO gas in the vicinity of the BH is highly excited, particularly at the interface between the BH outflow and the regions of triggered star formation. This suggests that the cold molecular gas is being shocked by the bipolar outflow from the BH, supporting the case for positive BH feedback.

Keywords: Active galaxies, Dwarf galaxies, Interstellar medium
Dust Polarization of Prestellar and Protostellar Sources in OMC-3. We present the Atacama Large Millimeter/submillimeter Array observations of linearly polarized 1.1 mm continuum emission at ∼0.″14 (55 au) resolution and CO (J = 2‑1) emission at ∼1.″5 (590 au) resolution toward one prestellar (MMS 4), four Class 0 (MMS 1, MMS 3, MMS 5, and MMS 6), one Class I (MMS 7), and one flat-spectrum (MMS 2) sources in the Orion Molecular Cloud 3 region. The dust disk-like structures and clear CO outflows are detected toward all sources except for MMS 4. The diameters of these disk-like structures, ranging from 16 to 97 au, are estimated based on the deconvolved full width half maximum (FWHM) values obtained from the multi-Gaussian fitting. Polarized emissions are detected toward MMS 2, MMS 5, MMS 6, and MMS 7, while no polarized emission is detected toward MMS 1, MMS 3, and MMS 4. MMS 2, MMS 5, and MMS 7 show organized polarization vectors aligned with the minor axes of the disk-like structures, with mean polarization fractions ranging from 0.6% to 1.2%. The strongest millimeter source, MMS 6, exhibits complex polarization orientations and a remarkably high polarization fraction of ∼10% around the Stokes I peak, and 15%–20% on the arm-like structure, as reported by Takahashi et al. (2019). The origins of the polarized emission, such as self-scattering and dust alignment due to the magnetic field or radiative torque, are discussed for individual sources. Some disk-like sources exhibit a polarized intensity peak shift toward the nearside of the disk, which supports that the polarized emission originates from self-scattering.

Keywords: Young stellar objects, Dust continuum emission, Polarimetry