A Correlation between Galaxy Morphology and MgiiHalo Absorption Strength

(Abridged) We compared the quantified morphological properties of 37intermediate redshift MgII absorption selected galaxies to the properties ofthe absorbing halo gas, observed in the spectra of background quasars. Thegalaxy morphologies were measured using GIM2D modeling of Hubble SpaceTelescope WFPC-2 images and the absorbing gas properties were obtained fromHIRES/Keck and UVES/VLT quasar spectra. We found a 3.1 sigma correlationbetween galaxy morphological asymmetries normalized by the quasar-galaxyprojected separations, A/D, and the MgII rest-frame equivalent widths.Saturation effects cause increased scatter in the relationship with increasingW_r(2796). We defined a subsample for which the fraction of saturated pixels inthe absorption profiles is f_sat<0.5. The correlation strengthened to 3.3sigma. We also find a paucity of small morphological asymmetries for galaxiesselected by MgII absorption as compared to those of the general population offield galaxies, as measured in the Medium Deep Survey. The K-S probability thatthe two samples are drawn from the same galaxy population is ruled out at a99.8% confidence level. The A/D-W_r(2796) correlation suggests a connectionbetween the processes that perturb galaxies and the quantity of gas in theirhalos, normalized by the impact parameter. Since the perturbations are minor,it is clear that dramatic processes or events are not required for a galaxy tohave an extended halo; the galaxies appear "normal". We suggest that common,more mild processes that populate halos with gas, such as satellite galaxymerging, accretion of the local cosmic web, and longer-range galaxy-galaxyinteractions, consequently also induce the observed minor perturbations in thegalaxies.Comment: Accepted for publication in the Astrophysical Journa