Measuring the halo mass of Mg II absorbers from their cross-correlation with Luminous Red Galaxies

Abstract

Abstract. We study the cross-correlation between 716 Mg II quasar absorption systems and ∼ 100,000 Luminous Red Galaxies (LRGs) selected from the Sloan Digital Sky Survey Data Release 3 in the redshift range 0.4 z 0.8. The Mg II systems were selected to have λλ2796 & 2803 rest-frame equivalent widths 1.0Å and identifications confirmed by the Fe II λ2600 or Mg I λ2852 lines. Over co-moving scales 0.2-13h −1 Mpc, the Mg II-LRG cross-correlation has an amplitude 0.69 ± 0.09 times that of the LRG-LRG auto-correlation. Since LRGs have halo-masses of 10 13 M⊙, this strong cross-correlation signal implies that the absorber host-galaxies have halo-masses 1-2 × 10 12 M⊙.