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1. The Plane Quasar Survey: First Data Release

   https://doi.org/10.3847/1538-4365/ad58df  

   Werk, Jessica; Tchernyshyov, Kirill; Bish, Hannah; Zheng, Yong; Putman, Mary; Peek, Joshua; Schiminovich, David (July 2024, The Astrophysical Journal Supplement Series)

   Abstract We present a sample of 305 QSO candidates having ∣b∣ < 30°, the majority with GALEX magnitudes near-UV < 18.75. To generate this sample, we apply UV–IR color selection criteria to photometric data from the Ultraviolet Galactic Plane Survey as part of GALEX-CAUSE, the Million Quasars Catalog, Gaia DR2, and Pan-STARRS DR1. 165 of these 305 candidate UV-bright active galactic nuclei (AGN; 54%) have published spectroscopic redshifts from 45 different surveys, confirming them as AGN. We further obtained low-dispersion, optical, long-slit spectra with the Apache Point Observatory 3.5 m, MDM 2.4 m, and MDM 1.3 m telescopes for 84 of the candidates, and confirm 86% (N= 72) as AGN, generally withz< 0.6. Of these 72 confirmed AGN, 25 are newly discovered low-latitude QSOs without any previous spectroscopy. These sources fill a gap in the Galactic latitude coverage of the available samples of known UV-bright QSO background probes. Along with a description of the confirmed QSO properties, we provide the fully reduced, flux- and wavelength-calibrated spectra of 72 low-latitude QSOs through the Mikulski Archive for Space Telescopes. Future Hubble Space Telescope/Cosmic Origins Spectrograph spectroscopy of these low-Galactic-latitude QSOs has the potential to transform our view of the Milky Way and Local Group circumgalactic medium. 

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2. The WISE-2MASS Survey: Red Quasars Into the Radio Quiet Regime

   https://doi.org/10.3847/1538-4357/ac6bee  

   Glikman, E.; Lacy, M.; LaMassa, S.; Bradley, C.; Djorgovski, S. G.; Urrutia, T.; Gates, E. L.; Graham, M. J.; Urry, M.; Yoon, I. (July 2022, The Astrophysical Journal)

   Abstract We present a highly complete sample of broad-line (Type 1) QSOs out to z ∼ 3 selected by their mid-infrared colors, a method that is minimally affected by dust reddening. We remove host-galaxy emission from the spectra and fit for excess reddening in the residual QSOs, resulting in a Gaussian distribution of colors for unreddened (blue) QSOs, with a tail extending toward heavily reddened (red) QSOs, defined as having E ( B − V ) > 0.25. This radio-independent selection method enables us to compare red and blue QSO radio properties in both the FIRST (1.4 GHz) and VLASS (2–4 GHz) surveys. Consistent with recent results from optically selected QSOs from SDSS, we find that red QSOs have a significantly higher detection fraction and a higher fraction of compact radio morphologies at both frequencies. We employ radio stacking to investigate the median radio properties of the QSOs including those that are undetected in FIRST and VLASS, finding that red QSOs have significantly brighter radio emission and steeper radio spectral slopes compared with blue QSOs. Finally, we find that the incidence of red QSOs is strongly luminosity dependent, where red QSOs make up >40% of all QSOs at the highest luminosities. Overall, red QSOs comprise ∼40% of higher luminosity QSOs, dropping to only a few percent at lower luminosities. Furthermore, red QSOs make up a larger percentage of the radio-detected QSO population. We argue that dusty AGN-driven winds are responsible for both the obscuration as well as excess radio emission seen in red QSOs. 

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3. Strong lensed QSOs with variability detectable by LSST: How many are there?

   https://doi.org/10.1093/mnras/stad2201  

   Taak, Yoon Chan; Treu, Tommaso (July 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Strong lensed quasi-stellar objects (QSOs) are valuable probes of the Universe in numerous aspects. Two of these applications, reverberation mapping and measuring time delays for determining cosmological parameters, require the source QSOs to be variable with sufficient amplitude. In this paper, we forecast the number of strong lensed QSOs with sufficient variability to be detected by the Vera C. Rubin Telescope Legacy Survey of Space and Time (LSST). The damped random walk model is employed to model the variability amplitude of lensed QSOs taken from a mock catalogue by Oguri & Marshall (2010). We expect 30–40 per cent of the mock lensed QSO sample, which corresponds to ∼1000, to exhibit variability detectable with LSST. A smaller subsample of 250 lensed QSOs will show larger variability of >0.15 mag for bright lensed images with i < 21 mag, allowing for monitoring with smaller telescopes. We discuss systematic uncertainties in the prediction by considering alternative prescriptions for variability and mock lens catalogue with respect to our fiducial model. Our study shows that a large-scale survey of lensed QSOs can be conducted for reverberation mapping and time delay measurements following up on LSST. 

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4. First HETDEX Spectroscopic Determinations of Lyα and UV Luminosity Functions at z = 2–3: Bridging a Gap between Faint AGNs and Bright Galaxies

   https://doi.org/10.3847/1538-4357/ac1e97  

   Zhang, Yechi; Ouchi, Masami; Gebhardt, Karl; Mentuch Cooper, Erin; Liu, Chenxu; Davis, Dustin; Jeong, Donghui; Farrow, Daniel J.; Finkelstein, Steven L.; Gawiser, Eric; et al (November 2021, The Astrophysical Journal)

   Abstract We present Ly α and ultraviolet (UV)-continuum luminosity functions (LFs) of galaxies and active galactic nuclei (AGNs) at z = 2.0–3.5 determined by the untargeted optical spectroscopic survey of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg 2 of fiber spectra sky coverage, obtaining 18,320 galaxies spectroscopically identified with Ly α emission, 2126 of which host type 1 AGNs showing broad (FWHM > 1000 km s −1 ) Ly α emission lines. We derive the Ly α (UV) LF over 2 orders of magnitude covering bright galaxies and AGNs in log L Ly α / [ erg s − 1 ] = 43.3 – 45.5 (−27 < M UV < −20) by the 1/ V max estimator. Our results reveal that the bright-end hump of the Ly α LF is composed of type 1 AGNs. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be α Sch = − 1.70 − 0.14 + 0.13 , which indicates that α Sch steepens from z = 2–3 toward high redshift. Our UV LF agrees well with previous AGN UV LFs and extends to faint-AGN and bright-galaxy regimes. The number fraction of Ly α -emitting objects ( X LAE ) increases from M UV * ∼ − 21 to bright magnitude due to the contribution of type 1 AGNs, while previous studies claim that X Ly α decreases from faint magnitudes to M UV * , suggesting a valley in the X Ly α –magnitude relation at M UV * . Comparing our UV LF of type 1 AGNs at z = 2–3 with those at z = 0, we find that the number density of faint ( M UV > −21) type 1 AGNs increases from z ∼ 2 to 0, as opposed to the evolution of bright ( M UV < −21) type 1 AGNs, suggesting AGN downsizing in the rest-frame UV luminosity. 

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5. Identifying Active Galactic Nuclei at z ∼ 3 from the HETDEX Survey Using Machine Learning

   https://doi.org/10.3847/1538-3881/acba92  

   Tardugno Poleo, Valentina; Finkelstein, Steven L.; Leung, Gene; Mentuch Cooper, Erin; Gebhardt, Karl; Farrow, Daniel J.; Gawiser, Eric; Zeimann, Greg; Schneider, Donald P.; Morabito, Leah; et al (March 2023, The Astronomical Journal)

   Abstract We used data from the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) to study the incidence of AGN in continuum-selected galaxies at z ∼ 3. From optical and infrared imaging in the 24 deg 2 Spitzer HETDEX Exploratory Large Area survey, we constructed a sample of photometric-redshift selected z ∼ 3 galaxies. We extracted HETDEX spectra at the position of 716 of these sources and used machine-learning methods to identify those which exhibited AGN-like features. The dimensionality of the spectra was reduced using an autoencoder, and the latent space was visualized through t-distributed stochastic neighbor embedding. Gaussian mixture models were employed to cluster the encoded data and a labeled data set was used to label each cluster as either AGN, stars, high-redshift galaxies, or low-redshift galaxies. Our photometric redshift (photo z ) sample was labeled with an estimated 92% overall accuracy, an AGN accuracy of 83%, and an AGN contamination of 5%. The number of identified AGN was used to measure an AGN fraction for different magnitude bins. The ultraviolet (UV) absolute magnitude where the AGN fraction reaches 50% is M UV = −23.8. When combined with results in the literature, our measurements of AGN fraction imply that the bright end of the galaxy luminosity function exhibits a power law rather than exponential decline, with a relatively shallow faint-end slope for the z ∼ 3 AGN luminosity function. 

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