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ABSTRACT Determining black hole masses and accretion rates with better accuracy and precision is crucial for understanding quasars as a population. These are fundamental physical properties that underpin models of active galactic nuclei. A primary technique to measure the black hole mass employs the reverberation mapping of low-redshift quasars, which is then extended via the radius–luminosity relationship for the broad-line region to estimate masses based on single-epoch spectra. An updated radius–luminosity relationship incorporates the flux ratio of optical Fe ii to H β ($$\equiv \mathcal {R}_{\rm Fe}$$) to correct for a bias in which more highly accreting systems have smaller line-emitting regions than previously realized. In this work, we demonstrate and quantify the effect of using this Fe-corrected radius-luminosity relationship on mass estimation by employing archival data sets possessing rest-frame optical spectra over a wide range of redshifts. We find that failure to use an Fe-corrected radius predictor results in overestimated single-epoch black hole masses for the most highly accreting quasars. Their accretion rate measures (LBol/LEdd and $$\dot{\mathscr{M}}$$ ) are similarly underestimated. The strongest Fe-emitting quasars belong to two classes: high-z quasars with rest-frame optical spectra, which, given their extremely high luminosities, require high accretion rates, and their low-z analogues, which, given their low black holes masses, must have high accretion rates to meet survey flux limits. These classes have mass corrections downward of about a factor of two, on average. These results strengthen the association of the dominant Eigenvector 1 parameter $$\mathcal {R}_{\rm Fe}$$ with the accretion process. 

Abstract The most reliable single-epoch supermassive black hole mass (M_BH) estimates in quasars are obtained by using the velocity widths of low-ionization emission lines, typically the Hβλ4861 line. Unfortunately, this line is redshifted out of the optical band atz≈ 1, leavingM_BHestimates to rely on proxy rest-frame ultraviolet (UV) emission lines, such as Civλ1549 or Mgiiλ2800, which contain intrinsic challenges when measuring, resulting in uncertainM_BHestimates. In this work, we aim at correctingM_BHestimates derived from the Civand Mgiiemission lines based on estimates derived from the Hβemission line. We find that employing the equivalent width of Civin derivingM_BHestimates based on Mgiiand Civprovides values that are closest to those obtained from Hβ. We also provide prescriptions to estimateM_BHvalues when only Civ, only Mgii, and both Civand Mgiiare measurable. We find that utilizing both emission lines, where available, reduces the scatter of UV-basedM_BHestimates by ∼15% when compared to previous studies. Lastly, we discuss the potential of our prescriptions to provide more accurate and precise estimates ofM_BHgiven a much larger sample of quasars at 3.20 ≲z≲ 3.50, where both Mgiiand Hβcan be measured in the same near-infrared spectrum. 

Abstract Quasars atz≳ 1 most often have redshifts measured from rest-frame ultraviolet emission lines. One of the most common such lines, Civλ1549, shows blueshifts up to ≈5000 km s⁻¹and in rare cases even higher. This blueshifting results in highly uncertain redshifts when compared to redshift determinations from rest-frame optical emission lines, e.g., from the narrow [Oiii]λ5007 feature. We present spectroscopic measurements for 260 sources at 1.55 ≲z≲ 3.50 having −28.0 ≲M_i≲ − 30.0 mag from the Gemini Near Infrared Spectrograph–Distant Quasar Survey (GNIRS-DQS) catalog, augmenting the previous iteration, which contained 226 of the 260 sources whose measurements are improved upon in this work. We obtain reliable systemic redshifts based on [Oiii]λ5007 for a subset of 121 sources, which we use to calibrate prescriptions for correcting UV-based redshifts. These prescriptions are based on a regression analysis involving Civfull-width-at-half-maximum intensity and equivalent width, along with the UV continuum luminosity at a rest-frame wavelength of 1350 Å. Applying these corrections can improve the accuracy and the precision in the Civ-based redshift by up to ∼850 km s⁻¹and ∼150 km s⁻¹, respectively, which correspond to ∼8.5 and ∼1.5 Mpc in comoving distance atz= 2.5. Our prescriptions also improve the accuracy of the best available multifeature redshift determination algorithm by ∼100 km s⁻¹, indicating that the spectroscopic properties of the Civemission line can provide robust redshift estimates for high-redshift quasars. We discuss the prospects of our prescriptions for cosmological and quasar studies utilizing upcoming large spectroscopic surveys. 

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. 

Abstract We report the first results of a high-redshift (z≳ 5) quasar survey using the Dark Energy Spectroscopic Instrument (DESI). As a DESI secondary target program, this survey is designed to carry out a systematic search and investigation of quasars at 4.8 <z< 6.8. The target selection is based on the DESI Legacy Imaging Surveys (the Legacy Surveys) DR9 photometry, combined with the Pan-STARRS1 data andJ-band photometry from public surveys. A first quasar sample has been constructed from the DESI Survey Validation 3 (SV3) and first-year observations until 2022 May. This sample includes more than 400 new quasars at redshift 4.7 ≤z< 6.6, down to 21.5 magnitude (AB) in thezband, discovered from 35% of the entire target sample. Remarkably, there are 220 new quasars identified atz≥ 5, more than one-third of existing quasars previously published at this redshift. The observations so far result in an average success rate of 23% atz> 4.7. The current spectral data set has already allowed analysis of interesting individual objects (e.g., quasars with damped Lyαabsorbers and broad absorption line features), and statistical analysis will follow the survey’s completion. A set of science projects will be carried out leveraging this program, including quasar luminosity function, quasar clustering, intergalactic medium, quasar spectral properties, intervening absorbers, and properties of early supermassive black holes. Additionally, a sample of 38 new quasars atz∼ 3.8–5.7 discovered from a pilot survey in the DESI SV1 is also published in this paper. 

ABSTRACT We present the steps taken to produce a reliable and complete input galaxy catalogue for the Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey (BGS) using the photometric Legacy Survey DR8 DECam. We analyse some of the main issues faced in the selection of targets for the DESI BGS, such as star–galaxy separation, contamination by fragmented stars and bright galaxies. Our pipeline utilizes a new way to select BGS galaxies using Gaia photometry and we implement geometrical and photometric masks that reduce the number of spurious objects. The resulting catalogue is cross-matched with the Galaxy And Mass Assembly (GAMA) survey to assess the completeness of the galaxy catalogue and the performance of the target selection. We also validate the clustering of the sources in our BGS catalogue by comparing with mock catalogues and the Sloan Digital Sky Survey (SDSS) data. Finally, the robustness of the BGS selection criteria is assessed by quantifying the dependence of the target galaxy density on imaging and other properties. The largest systematic correlation we find is a 7 per cent suppression of the target density in regions of high stellar density. 

Abstract The DESI Milky Way Survey (MWS) will observe ≥8 million stars between 16 < r < 19 mag, supplemented by observations of brighter targets under poor observing conditions. The survey will permit an accurate determination of stellar kinematics and population gradients, characterize diffuse substructure in the thick disk and stellar halo, enable the discovery of extremely metal-poor stars and other rare stellar types, and improve constraints on the Galaxy’s 3D dark matter distribution from halo star kinematics. MWS will also enable a detailed characterization of the stellar populations within 100 pc of the Sun, including a complete census of white dwarfs. The target catalog from the preliminary selection described here is public (Available at https://data.desi.lbl.gov/public/ets/target/catalogs/and detailed at  https://desidatamodel.readthedocs.io).