Identifying Missing Quasars from the DESI Bright Galaxy Survey

Journal Article · Wed Feb 19 00:00:00 UTC 2025 · The Astronomical Journal

DOI: https://doi.org/10.3847/1538-3881/adabc9 · OSTI ID:3009751

Juneau, S. ; Canning, R.; Alexander, D. M. ; Pucha, R. ; Fawcett, V. A. ; Myers, A. D.; Moustakas, J. ; Ruiz-Macias, O.; Cole, S. ; Pan, Z. ; Aguilar, J.; Ahlen, S. ; Alam, S. ; Bailey, S. ; Brooks, D.; Chaussidon, E. ; Circosta, C.; Claybaugh, T.; Davis, T. M. ; Dawson, K. ; de la Macorra, A. ; Dey, Arjun ; Doel, P.; Fanning, K. ; Forero-Romero, J. E. ; Gaztañaga, E.; Gontcho A Gontcho, S. ; Gutierrez, G.; Hahn, C. ; Honscheid, K.; Kehoe, R.; Kisner, T. ; Kremin, A. ; Lambert, A.; Landriau, M. ; Le Guillou, L. ; Manera, M. ; Martini, P. ; Meisner, A. ; Miquel, R.; Muñoz-Gutiérrez, A.; Nie, J. ; Palanque-Delabrouille, N. ; Percival, W. J. ; Poppett, C.; Prada, F. ; Ravoux, C. ; Rezaie, M. ; Rossi, G.; Sanchez, E. ; Schlafly, E. F. ; Schlegel, D.; Schubnell, M.; Seo, H. ; Silber, J. ; Siudek, M. ; Sprayberry, D.; Tan, T. ; Tarlé, G. ; Yèche, C. ; Zhou, Z. ; Zou, H.

The Dark Energy Spectroscopic Instrument (DESI) cosmology survey includes a Bright Galaxy Survey (BGS), which will yield spectra for over 10 million bright galaxies (r < 20.2 AB mag). The resulting sample will be valuable for both cosmological and astrophysical studies. However, the star/galaxy separation criterion implemented in the nominal BGS target selection algorithm excludes quasar host galaxies in addition to bona fide stars. While this excluded population is comparatively rare (∼3–4 per square degrees), it may hold interesting clues regarding galaxy and quasar physics. Therefore, we present a target selection strategy that was implemented to recover these missing active galactic nuclei (AGN) from the BGS sample. The design of the selection criteria was both motivated and confirmed using spectroscopy. The resulting BGS-AGN sample is uniformly distributed over the entire DESI footprint. According to DESI survey validation data, the sample comprises 93% quasi-stellar objects (QSOs), 3% narrow-line AGN or blazars with a galaxy contamination rate of 2%, and a stellar contamination rate of 2%. Peaking around redshift z = 0.5, the BGS-AGN sample is intermediary between quasars from the rest of the BGS and those from the DESI QSO sample in terms of redshifts and AGN luminosities. The stacked spectrum is nearly identical to that of the DESI QSO targets, confirming that the sample is dominated by quasars. We highlight interesting small populations reaching z > 2, which are either faint quasars with nearby projected companions or very bright quasars with strong absorption features including the Lyα forest, metal absorbers, and/or broad absorption lines.

• Research Organization: Andes U., Bogota; BCCP, Berkeley; Baltimore, Space Telescope Sci.; Barcelona, Autonoma U.; Barcelona, IEEC; Barcelona, IFAE; Beijing Observ.; Boston U.; Chicago U., KICP; Clemson U.; Durham U.; Durham U., ICC; Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Granada U., Theor. Phys. Astrophys.; ICREA, Barcelona; IRFU, Saclay; Kansas State U.; LPC, Clermont-Ferrand; LPNHE, Paris; LSST, Tucson; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Madrid, CIEMAT; Marseille, CPPM; Michigan U.; Natl. Solar Observ., Tucson; Newcastle upon Tyne U.; Ohio State U.; Ohio State U., Dept. Astron.; Ohio U., Athens; Perimeter Inst. Theor. Phys.; Portsmouth U., ICG; Princeton U.; SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Sejong U.; Siena Coll., Loudonville; Southern Methodist U.; TIFR, Mumbai, DHEP; Tsinghua U., Beijing, CHEP; U. Michigan, Ann Arbor; UC, Berkeley, Space Sci. Dept.; UNAM, Mexico; Univ. of Utah, Salt Lake City, UT (United States); University Coll. London; University of Michigan, Ann Arbor, MI (United States); University of Wyoming, Laramie, WY (United States); Utah U.; Waterloo U.; Wyoming U.
• Sponsoring Organization: National Science Foundation (NSF); Science Technology Facilities Council (STFC); U.S. National Science Foundation (NSF); U.S. National Science Foundation (NSF), Division of Astronomical Sciences; US Department of Energy; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), High Energy Physics (HEP); USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25); United Kingdom Research and Innovation; United Kingdom Research and Innovation grant
• Grant/Contract Number: 89243024CSC000002; AC02-05CH11231; AC02-76SF00515; SC0009959; SC0019022; SC0019193; SC0020086
• OSTI ID: 3009751
• Report Number(s): FERMILAB-PUB--24-0145-PPD; FERMILAB-PUB-24-0145-PPD; arXiv:2404.03621
• Journal Information: The Astronomical Journal, Journal Name: The Astronomical Journal Journal Issue: 3 Vol. 169; ISSN 0004-6256; ISSN 1538-3881
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English