Identifying Circumgalactic Medium Absorption in QSO Spectra: A Bayesian Approach

We present a study of candidate galaxy–absorber pairs for 43 low-redshift QSO sightlines (0.06 < z < 0.85) observed with the Hubble Space Telescope/Cosmic Origins Spectrograph that lie within the footprint of the Sloan Digital Sky Survey with a statistical approach to match absorbers with gala...

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Bibliographic Details
Published in:The Astrophysical journal 2021-12, Vol.923 (1), p.44
Main Authors: Scott, Jennifer E., Shoemaker, Emileigh S., Hamill, Colin D.
Format: Article
Language:English
Subjects:
Absorbers
Astronomy & Astrophysics
ASTRONOMY AND ASTROPHYSICS
Astrophysics
Bayesian analysis
Circumgalactic medium
Galactic and extragalactic astronomy
Galaxies
Hubble Space Telescope
Intergalactic medium
Luminosity
Median (statistics)
Photometry
Red shift
Sky surveys (astronomy)
Space telescopes
Spectroscopic analysis
Stars & galaxies
Statistical methods
Stellar mass
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Summary:We present a study of candidate galaxy–absorber pairs for 43 low-redshift QSO sightlines (0.06 < z < 0.85) observed with the Hubble Space Telescope/Cosmic Origins Spectrograph that lie within the footprint of the Sloan Digital Sky Survey with a statistical approach to match absorbers with galaxies near the QSO lines of sight using only the SDSS Data Release 12 photometric data for the galaxies, including estimates of their redshifts. Our Bayesian methods combine the SDSS photometric information with measured properties of the circumgalactic medium to find the most probable galaxy match, if any, for each absorber in the line-of-sight QSO spectrum. We find ∼630 candidate galaxy–absorber pairs using two different statistics. The methods are able to reproduce pairs reported in the targeted spectroscopic studies upon which we base the statistics at a rate of 72%. The properties of the galaxies comprising the candidate pairs have median redshift, luminosity, and stellar mass, all estimated from the photometric data, z = 0.13, L = 0.1 L * , and log ( M * / M ⊙ ) = 9.7 . The median impact parameter of the candidate pairs is ∼430 kpc, or ∼3.5 times the galaxy virial radius. The results are broadly consistent with the high Ly α covering fraction out to this radius found in previous studies. This method of matching absorbers and galaxies can be used to prioritize targets for spectroscopic studies, and we present specific examples of promising systems for such follow-up.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac2954