Probing the cool interstellar and circumgalactic gas of three massive lensing galaxies atz= 0.4–0.7

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 * /M = 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 r e 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 HE 0435−1223 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 HE 0047−1756, and in one of the two sightlines near the double lens for HE 1104−1805. The absorbers are resolved into 8 − 15 individual components with a line-of-sight velocity spread of ∆ v ≈ 300 − 600 km s −1 . The large ionic column densities, log N > ∼ 14, observed in two components suggest that these may be Lyman limit or damped Lyα 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 ∆ v 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 multisightline approach provide a powerful tool to resolve the origin of chemically-enriched cool gas in massive halos.

The Circumgalactic Medium in Massive Halos

“…This is in stark contrast to an α-element enhanced chemical composition found in young, star-forming galaxies (Dessauges-Zavadsky et al, 2004;Crighton et al, 2013;Fox et al, 2014, e.g. ) and see Zahedy et al (2016a) for a detailed comparison, and clearly indicates different origins between gas associated with star-forming galaxies and with massive quiescent galaxies.…”

“…Rigby et al, 2002;Narayanan et al, 2008;Zahedy et al, 2016a). Similarly, the Mg II doublet transitions enable accurate Mg II column density measurements N(Mg II ) for all but a few saturated components.…”

“…Mathews & Brighenti, 2003;Humphrey & Buote, 2006). Therefore, it seems likely that the observed Fe-rich gas at d ≈ r e from the lenses originates in the ISM of these massive galaxies, where SNe Ia play a dominant role in driving the observed large velocity width and Fe-rich abundance pattern (Zahedy et al, 2016a). If the ISM of massive galaxies at intermediate redshift is locally enriched by SNe Ia, then the observed Fe/Mg is expected to decline with increasing projected distance.…”

“…This exercise demonstrates that useful empirical constraints for the relative Fe and Mg abundances can be obtained even in the absence of accurate measurements of N(H I) and gas metallicity. A recent study utilizing multiply-lensed QSOs for probing gas at small projected distances, d < ∼ 20 kpc or ≈ 1 − 2 effective radii r e , from the lensing galaxies has uncovered important new clues for the origin of chemically-enriched cool gas in massive halos (Zahedy et al, 2016a). These lensing galaxies at z = 0.4 − 0.7 share similar properties concerning both the quiescent state and halo mass scales (M h > ∼ 10 13 M ), but display distinct absorption-line profiles between different lensing galaxies and between different sightlines of individual lenses.…”

Quasar lenses and pairs in the VST-ATLAS and Gaia

“…Oguri et al 2014); (ii) a magnified view of the background quasar, accretion disk, and host galaxy (Peng et al 2006;Sluse et al 2015;Motta et al 2017;Ding et al 2017); (iii) information about distances and thus cosmological parameters (Refsdal 1964;Cárdenas et al 2013;Treu & Marshall 2016;Suyu et al 2017). Spectroscopy of close sightlines, be they to multiple quasar images or to pairs of physically distinct quasars, is a probe of: (i) kinematics of the cosmic web at high redshift (Rauch et al 2005); (ii) small-scale structure of Lyα absorbers (Smette et al 1992;Dinshaw et al 1998;Rorai et al 2017); (iii) physical conditions of the cool ISM/CGM of galaxies and quasars (Farina et al 2014;Zahedy et al 2016).…”