A Correlation between Galaxy Morphology and Mg II Halo Absorption Strength

We compared the quantified morphological properties of 37 intermediate redshift Mg II absorption selected galaxies to the properties of the absorbing halo gas [0.03 Å ≤ W_r(2796) ≤ 2.90 Å], observed in the spectra of background quasars. The galaxy morphologies were measured using GIM2D modeling of Hubble Space Telescope WFPC2 images and the absorbing gas properties were obtained from Keck HIRES and VLT UVES quasar spectra. We found a 3.1 σ correlation between galaxy morphological asymmetries normalized by the quasar-galaxy projected separations, A/D, and the Mg II rest-frame equivalent widths. Saturation effects cause increased scatter in the relationship with increasing W_r(2796). We defined a subsample of 28 systems for which the fraction of saturated pixels in the absorption profiles is f_sat < 0.5. The correlation strengthened to 3.3 σ. We also find a paucity of small morphological asymmetries for galaxies selected by Mg II absorption as compared to those of the general population of field galaxies, as measured in the Medium Deep Survey. The K-S probability that the two samples are drawn from the same galaxy population is ruled out at a 99.8% confidence level. The A/D-W_r(2796) correlation suggests a connection between the processes that perturb galaxies and the quantity of gas in their halos, normalized by the impact parameter. It is clear that dramatic processes or events are not required for a galaxy to have an extended halo; the galaxies appear ``normal.'' We suggest that processes that populate halos with gas, such as satellite galaxy merging, accretion of the local cosmic web, and longer range galaxy-galaxy interactions, also induce the observed minor perturbations in the galaxies.