Probing the Cool Interstellar and Circumgalactic Gas of Three Massive Lensing Galaxies at z=0.4-0.7

TL;DR

This study uses multi-sightline absorption spectroscopy to investigate the properties and origins of cool gas in the halos of three massive, quiescent lensing galaxies at redshifts 0.4-0.7, revealing diverse gas absorption features and enrichment patterns.

Contribution

It provides the first multi-sightline analysis of cool gas around distant passive elliptical galaxies, highlighting the role of SNe Ia in enriching halo gas and demonstrating the power of this approach to understand gas origins.

Findings

Diverse absorption features among different lens sightlines.

Detection of large velocity spreads and super-solar Fe/Mg ratios.

Evidence for SNe Ia enrichment in the halo gas.

Abstract

We present multi-sightline absorption spectroscopy of cool gas around three lensing galaxies at z=0.4-0.7. These lenses have half-light radii r_e=2.6-8 kpc and stellar masses of log M*/Ms=10.9-11.4, and therefore resemble nearby passive elliptical galaxies. The lensed QSO sightlines presented here occur at projected distances of d=3-15 kpc (or d~1-2 r_e) from the lensing galaxies, providing for the first time an opportunity to probe both interstellar gas at r~r_e and circumgalactic gas at larger radii r>>re of these distant quiescent galaxies. We observe distinct gas absorption properties among different lenses and among sightlines of individual lenses. Specifically, while the quadruple lens for HE0435-1223 shows no absorption features to very sensitive limits along all four sightlines, strong Mg II, Fe II, Mg I, and Ca II absorption transitions are detected along both sightlines near the double lens for HE0047-1756, and in one of the two sightlines near the double lens for HE1104-1805. The absorbers are resolved into 8-15 individual components with a line-of-sight velocity spread of dv~300-600 km/s. The large ionic column densities, log N>14, observed in two components suggest that these may be Lyman limit or damped Lya absorbers with a significant neutral hydrogen fraction. The majority of the absorbing components exhibit a uniform super solar Fe/Mg ratio with a scatter of <0.1 dex across the full dv range. Given a predominantly old stellar population in these lensing galaxies, we argue that the observed large velocity width and Fe-rich abundance pattern can be explained by SNe Ia enriched gas at radius r~r_e. We show that additional spatial constraints in line-of-sight velocity and relative abundance ratios afforded by a multi-sightline approach provide a powerful tool to resolve the origin of chemically-enriched cool gas in massive halos.