An Exploratory Analysis of New Large Gaia-informed Quasar Samples in SDSS-V

Shir Aviram, Benny Trakhtenbrot, Tom Dwelly, Scott F. Anderson, Sean Morrison, Michael Eracleous, Yue Shen, Mara Salvato, Donald P. Schneider, Roberto J. Assef, Catarina Aydar, Franz E. Bauer, W. N. Brandt, Joel R. Brownstein, Johannes Buchner, Jeremy Darling, Jose G. Fernandez-Trincado, Patrick B. Hall, Dong-Woo Kim, Anton M. Koekemoer, Stephanie LaMassa, Andrea Merloni, Claudio Ricci, Qian Yang, Grisha Zeltyn

First listed 2026-07-31 | Last updated 2026-07-29

Abstract

Quasars are luminous objects that provide insights into the physics and evolution of supermassive black holes (SMBHs) and their accretion flows, galaxy evolution, and even cosmology. In this study, we present an exploratory study based on the ongoing fifth generation of the Sloan Digital Sky Survey (SDSS-V) and its unique dual-hemisphere, wide-field, and multi-object spectroscopic capabilities, with the aim of creating a comprehensive, all-sky quasar sample. The targets were selected through two novel methods, GUA and Skewt-QSO, that rely primarily on data from WISE and Gaia, aiming to address gaps in previous large quasar samples. Our sample includes over 250,000 spectroscopically confirmed quasars reaching z~5, with tens of thousands of newly identified quasars in the southern hemisphere. The selection methods are highly pure, with well over 80% of the spectra collected being genuine quasars; the main contaminants are M-type stars. The detailed spectral decomposition procedure we employed shows that the quasars in the sample span a wide range of luminosities (Lbol~$10^{44}-10^{48} erg s^{-1}$), SMBH masses (MBH~$10^6-10^{10}$ Msun), and accretion rates (L/LEdd~0.01-1). The distributions of these properties are consistent with those of previous quasar catalogs, which are based on past generations of SDSS, once we account for potential selection biases related to the various survey depths. Our findings confirm that novel selection methods based on optical+IR colors and/or astrometry can yield a large, high-purity quasar sample over wide sky areas, including in cases where more nuanced multi-band photometry and/or multi-wavelength data in the X-ray or radio is not available. This SDSS-V sample, which will continue to grow, establishes a robust reference for future southern (time-domain) surveys, while enhancing and complementing our understanding of quasar demographics and SMBH evolution.

Short digest

Aviram et al. present an exploratory SDSS-V quasar census built from the Gaia- and WISE-informed GUA and Skewt_QSO target selections, yielding more than 250,000 spectroscopically confirmed quasars to z≈5 and tens of thousands of new southern-sky identifications. Both selections are exceptionally pure, exceeding 96% in the reported homogenized efficiency analysis, with M-type stars the principal contaminants. PyQSOFit spectral decompositions place the sample across Lbol≈10^44–10^48 erg s^-1, MBH≈10^6–10^10 Msun, and L/LEdd≈0.01–1; after matching for survey-depth-driven brightness differences, its inferred black-hole and accretion-property distributions agree closely with SDSS/DR16Q. The work establishes optical+IR-color and astrometric targeting as a practical route to a wide-area, high-purity southern-hemisphere quasar reference sample for future time-domain surveys.

Key figures to inspect

• Figure 1. This flowchart defines the GUA and Skewt_QSO parent samples and traces how their Gaia- and WISE-informed candidate selections enter SDSS-V target cartons and the final analysis sets. It is the essential selection-function figure for interpreting the survey-scale claims.
• Figure 7. The all-sky maps make the paper's hemispheric contribution immediately visible, separating the two SDSS-V selections and highlighting newly identified quasars against prior Milliquas and DESI coverage. This figure best conveys the expansion of spectroscopic quasar coverage in the southern sky.
• Figure 9. The selection-efficiency comparison provides the paper's clearest quantitative headline: both GUA and Skewt_QSO attain homogenized quasar purities above 96%, with conservative lower limits also shown. It directly supports the claim that simple optical+IR and astrometric selection can deliver unusually clean large samples.
• Figure 18. By matching GUA quasars to SDSS/DR16Q in brightness and redshift, this figure shows that the apparent differences in luminosity, black-hole mass, and Eddington-ratio distributions are largely selection-depth effects. It is the key diagnostic underpinning the conclusion that the SDSS-V sample is demographically consistent with earlier SDSS quasar catalogs.