More Like this

1. Discovery of the most luminous quasar of the last 9 Gyr

   https://doi.org/10.1017/pasa.2022.36  

   Onken, Christopher A.; Lai; Wolf, Christian; Lucy, Adrian B.; Hon, Wei Jeat; Tisserand, Patrick; Sokoloski, Jennifer L.; Luna, Gerardo J.; Manick, Rajeev; Fan, Xiaohui; et al (January 2022, Publications of the Astronomical Society of Australia)

   Abstract We report the discovery of a bright ( $g = 14.5$ mag (AB), $K = 11.9$ mag (Vega)) quasar at redshift $z=0.83$ — the optically brightest (unbeamed) quasar at $z>0.4$ . SMSS J114447.77-430859.3, at a Galactic latitude of $$b=+18.1^{\circ}$$ , was identified by its optical colours from the SkyMapper Southern Survey (SMSS) during a search for symbiotic binary stars. Optical and near-infrared spectroscopy reveals broad Mg ii , H $$\unicode{x03B2}$$ , H $$\unicode{x03B1}$$ , and Pa $$\unicode{x03B2}$$ emission lines, from which we measure a black hole mass of $$\log_{10}\! (M_{\mathrm{BH}}/\mathrm{M}_{\odot}) = 9.4 \pm 0.5$$ . With its high luminosity, $$L_{\mathrm{bol}} = (4.7\pm1.0)\times10^{47}\,\mathrm{erg\,s}^{-1}$$ or $$M_{i}(z=2) = -29.74$$ mag (AB), we estimate an Eddington ratio of $$\approx1.4$$ . As the most luminous quasar known over the last $${\sim}$$ 9 Gyr of cosmic history, having a luminosity $$8\times$$ greater than 3C 273, the source offers a range of potential follow-up opportunities. 

   more » « less
2. Bridging Quasars and Little Red Dots: Insights into Broad-line Active Galactic Nuclei at z = 5–8 from the First JWST COSMOS-3D Dataset

   https://doi.org/10.3847/1538-4357/ae1b9b  

   Lin, Xiaojing; Fan, Xiaohui; Wang, Feige; Sun, Fengwu; Champagne, Jaclyn B; Egami, Eiichi; Kakiichi, Koki; Lyu, Jianwei; Tee, Wei Leong; Yang, Jinyi; et al (December 2025, The Astrophysical Journal)

   Abstract We report the discovery of 13 broad-line active galactic nuclei (AGNs) atz= 5–8 from the first 10% of JWST Cycle 3 Treasury Program COSMOS-3D. These AGNs are identified by their broad Hαor Hβemission lines through NIRCam grism slitless spectroscopy. One object atz= 7.646 with broad Hβemission has an F444W magnitude of 23.6 mag, making it one of the brightestz> 7.5 broad-line AGNs yet known. Among the 13 AGNs, 10 objects exhibit reddened optical continua with slopesβ_opt> 0. The remaining three resemble UV-luminous quasars at similar redshift but withβ_optless blue than those of typical unobscured quasars. We also obtain MIRI photometry (7.7–18μm) for two AGNs and place strong constraints on their rest-frame near-IR spectral energy distribution. We find no significant variability in the rest-frame UV by comparing the COSMOS-3D and COSMOS-Web F115W images taken apart by 60 days in the rest-frame. We compute the Hαluminosity function (LF) atz≈ 5–6 and find potential redshift evolution compared toz≈ 4–5. We also derive the HβLF atz∼ 8 by combining our sample with those from the literature. The broad Hβemitters in this work suggest a number density 2 orders of magnitude higher than that predicted by the quasar LF based on rest-frame UV-selected samples. As a preview, our work showcases the ability of the COSMOS-3D grism survey to provide a complete view of the properties, growth, and evolution of bright broad-line AGNs atz> 5. 

   more » « less
3. 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. 

   more » « less
4. Shedding New Light on Weak Emission-line Quasars in the C iv–Hβ Parameter Space

   https://doi.org/10.3847/1538-4357/acd04d  

   Ha, Trung; Dix, Cooper; Matthews, Brandon M.; Shemmer, Ohad; Brotherton, Michael S.; Myers, Adam D.; Richards, Gordon T.; Maithil, Jaya; Anderson, Scott F.; Brandt, W N; et al (June 2023, The Astrophysical Journal)

   Abstract Weak emission-line quasars (WLQs) are a subset of type 1 quasars that exhibit extremely weak Lyα+ Nvλ1240 and/or Civλ1549 emission lines. We investigate the relationship between emission-line properties and accretion rate for a sample of 230 “ordinary” type 1 quasars and 18 WLQs atz< 0.5 and 1.5 <z< 3.5 that have rest-frame ultraviolet and optical spectral measurements. We apply a correction to the Hβ-based black hole mass (M_BH) estimates of these quasars using the strength of the optical Feiiemission. We confirm previous findings that WLQs’M_BHvalues are overestimated by up to an order of magnitude using the traditional broad-emission-line region size–luminosity relation. With thisM_BHcorrection, we find a significant correlation between Hβ-based Eddington luminosity ratios and a combination of the rest-frame Civequivalent width and Civblueshift with respect to the systemic redshift. This correlation holds for both ordinary quasars and WLQs, which suggests that the two-dimensional Civparameter space can serve as an indicator of accretion rate in all type 1 quasars across a wide range of spectral properties. 

   more » « less
5. An empirical reionization history model inferred from the low-redshift Lyman continuum survey and the star-forming galaxies at z > 8

   https://doi.org/10.1093/mnras/stad3483  

   Lin, Yu-Heng; Scarlata, Claudia; Williams, Hayley; Chen, Wenlei; Kelly, Patrick; Langeroodi, Danial; Hjorth, Jens; Chisholm, John; Koekemoer, Anton M; Zitrin, Adi; et al (November 2023, Monthly Notices of the Royal Astronomical Society)

   We present a new analysis of the rest-frame ultraviolet (UV) and optical spectra of a sample of three z > 8 galaxies discovered behind the gravitational lensing cluster RX J2129.4+0009. We combine these observations with z > 7.5 galaxies from the literature, for which similar measurements are available. As already pointed out in other studies, the high [O iii]λ5007/[O ii]λ3727 ratios (O32) and steep UV continuum slopes (β) are consistent with the values observed for low-redshift Lyman continuum emitters, suggesting that such galaxies contribute to the ionizing budget of the intergalactic medium. We construct a logistic regression model to estimate the probability of a galaxy being a Lyman continuum emitter based on the measured MUV, β, and O32. Using this probability and the UV luminosity function, we construct an empirical model that estimates the contribution of high-redshift galaxies to reionization. The preferred scenario in our analysis shows that at z ∼ 8, the average escape fraction of the galaxy population [i.e. including both LyC emitters (LCEs) and non-emitters] varies with MUV, with intermediate UV luminosity (−19 < MUV < −16) galaxies having larger escape fraction. Galaxies with faint UV luminosity (−16 < MUV < −13.5) contribute most of the ionizing photons. The relative contribution of faint versus bright galaxies depends on redshift, with the intermediate UV galaxies becoming more important over time. UV bright galaxies, although more likely to be LCEs at a given log(O32) and β, contribute the least of the total ionizing photon budget. 

   more » « less