THE INCIDENCE OF COOL GAS IN {approx}10{sup 13} M{sub sun} HALOS
- Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, IL (United States)
We present the first results of an ongoing spectroscopic follow-up of close luminous red galaxies (LRGs) and Mg II {lambda}{lambda}2796,2803 absorber pairs for an initial sample of 15 photometrically selected LRGs at physical projected separations {rho} {approx_lt} 350 h {sup -1} kpc from a QSO sight line. Our moderate-resolution spectra confirm a physical association between the cool gas (T {approx} 10{sup 4} K) revealed by the presence of Mg II absorption features and the LRG halo in five cases. In addition, we report an empirical estimate of the maximum covering fraction ({kappa}{sub max}) of cool gas in massive, {approx_gt}10{sup 13} h {sup -1} M{sub sun} dark matter halos hosting LRGs at z {approx} 0.5. This study is performed using a sample of foreground LRGs that are located at {rho} < 400 h {sup -1} kpc from a QSO sight line. The LRGs are selected to have a robust photometric redshift {sigma}{sub z}/(1 + z{sub ph}) {approx_equal} 0.03. We determine {kappa}{sub max} based on the incidence of Mg II absorption systems that occur within z{sub ph} {+-} 3 {sigma}{sub z} in the spectra of the background QSOs. Despite the large uncertainties in z{sub ph}, this experiment provides a conservative upper limit to the covering fraction of cool gas in the halos of LRGs. We find that {kappa}{sub max} {approx} 0.07 at W{sub r} (2796) {>=} 1.0 A and {kappa}{sub max} {approx} 0.18 at W{sub r} (2796) {>=} 0.5 A, averaged over 400 h {sup -1} kpc radius. Our study shows that while cool gas is present in {approx_gt}10{sup 13} h {sup -1} M{sub sun} halos, the mean covering fraction of strong absorbers is no more than 7%.
- OSTI ID:
- 21452928
- Journal Information:
- Astrophysical Journal, Vol. 716, Issue 2; Other Information: DOI: 10.1088/0004-637X/716/2/1263; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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