Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-line Spectroscopy. II. Methods and Models

Journal Article · Mon May 01 04:00:00 EDT 2017 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.3847/1538-4365/AA6B59· OSTI ID:22872708

Keeney, Brian A.; Stocke, John T.; Danforth, Charles W.; Shull, J. Michael; Pratt, Cameron T.; Green, James C. ^[1]; Froning, Cynthia S. ^[2]; Penton, Steven V. ^[3]; Savage, Blair D. ^[4]

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1. Center for Astrophysics and Space Astronomy, Department of Astrophysical and Planetary Sciences, University of Colorado, 389 UCB, Boulder, CO 80309 (United States)
2. Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)
3. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
4. Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States)

We present basic data and modeling for a survey of the cool, photoionized circumgalactic medium (CGM) of low-redshift galaxies using far-UV QSO absorption-line probes. This survey consists of “targeted” and “serendipitous” CGM subsamples, originally described in Stocke et al. (Paper I). The targeted subsample probes low-luminosity, late-type galaxies at z<0.02 with small impact parameters (〈ρ〉=71 kpc), and the serendipitous subsample probes higher luminosity galaxies at z≲0.2 with larger impact parameters (〈ρ〉=222 kpc). Hubble Space Telescope and FUSE UV spectroscopy of the absorbers and basic data for the associated galaxies, derived from ground-based imaging and spectroscopy, are presented. We find broad agreement with the COS-Halos results, but our sample shows no evidence for changing ionization parameter or hydrogen density with distance from the CGM host galaxy, probably because the COS-Halos survey probes the CGM at smaller impact parameters. We find at least two passive galaxies with H i and metal-line absorption, confirming the intriguing COS-Halos result that galaxies sometimes have cool gas halos despite no on-going star formation. Using a new methodology for fitting H i absorption complexes, we confirm the CGM cool gas mass of Paper I, but this value is significantly smaller than that found by the COS-Halos survey. We trace much of this difference to the specific values of the low-z metagalactic ionization rate assumed. After accounting for this difference, a best-value for the CGM cool gas mass is found by combining the results of both surveys to obtain log(M/M{sub ⊙})=10.5±0.3, or ∼30% of the total baryon reservoir of an L⩾L{sup ∗}, star-forming galaxy.

• OSTI ID: 22872708
• Journal Information: Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 1 Vol. 230; ISSN 0067-0049; ISSN APJSA2
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
BARYONS
DISTANCE
GALAXIES
HYDROGEN
IMPACT PARAMETER
LUMINOSITY
MASS
METALS
PHOTOIONIZATION
RED SHIFT
SIMULATION
SPECTROSCOPY
STARS
TELESCOPES
ULTRAVIOLET RADIATION