Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21741204g&link_type=abstract
American Astronomical Society, AAS Meeting #217, #412.04; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
We present the first results of an ongoing spectroscopic follow-up of close luminous red galaxies (LRGs) and MgII λλ2796,2803 absorber pairs for an initial sample of 15 photometrically selected LRGs at physical projected separations ρ ≤ 350 h-1 kpc from a QSO sight line. Our moderate-resolution spectra confirm a physical association between the cool gas (T˜ 104 K) revealed by the presence of MgII absorption features and the LRG halo in five cases. In addition, we report an empirical estimate of the maximum covering fraction (κmax) of cool gas in massive,˜1013 h-1 Msun dark matter halos hosting LRGs at z 0.5. This study is performed using a sample of foreground LRGs that are located at ρ < 400 h-1 kpc from a QSO sight line. The LRGs are selected to have a robust photometric redshift σz(1+zph) ≈ 0.03.We determine κmax based on the incidence of MgII absorption systems that occur within zph ± 3 σzin the spectra of the background QSOs. Despite the large uncertainties in zph, this experiment provides a conservative upper limit to the covering fraction of cool gas in the halos of LRGs. We find that κmax ≈ 0.07 at Wr(2796) ≥ 1.0Ǻ and κmax ≈ 0.18 at Wr(2796) ≥ 0.5 Ǻ, averaged over 400 h-1 kpc radius. Our study shows that while cool gas is present in 1013 h-1 Msun halos, the mean covering fraction of strong absorbers is no more than 7%.
J.-R.G. acknowledges support from the Brinson Foundation predoctoral fellowship and from the Sigma-Xi Grant-in-Aid of Research program. H.-W. C. acknowledges partial support from NASA grant NNG06GC36G and NSF grant AST-0607510.
Chen Haibin
Gauthier Jean-Rene
Tinker Jeremy
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