Significant H I and metal differences around the z = 0.83 lens galaxy toward the doubly lensed quasar SBS 0909+532.
CASHMAN F.H., KULKARNI V.P. and LOPEZ S.
Abstract (from CDS):
We report a large difference in neutral hydrogen (H I) and metal column densities between the two sight lines probing opposite sides of the lensing galaxy at zlens = 0.83 toward the doubly lensed quasar SBS 0909+532. Using archival HST-STIS and Keck HIRES spectra of the lensed quasar images, we measure log N_H I_ = 18.77 ± 0.12 cm–2 toward the brighter image (A) at an impact parameter of rA = 3.15 kpc and log N_H I_ = 20.38 ± 0.20 cm–2 toward the fainter image (B) at an impact parameter of rB = 5.74 kpc. This difference by a factor of ∼41 is the highest difference between sight lines for a lens galaxy in which H I has been measured, suggesting patchiness and/or anisotropy on these scales. We estimate an average Fe abundance gradient between the sight lines to be >=+0.35 dex kpc–1. The N_Fe II/NMg II_ ratios for the individual components detected in the Keck HIRES spectra have supersolar values for all components in sight line A and for 11 out of 18 components in sight line B, suggesting that Type Ia supernovae may have contributed to the chemical enrichment of the galaxy's environment. Additionally, these observations provide complementary information to detections of cold gas in early-type galaxies and the tension between these and some models of cloud survival.