CGM² — Probing the Circumgalactic Medium of Low-redshift Galaxies Using QSO Spectroscopy

The COS and Gemini Mapping the Circumgalactic Medium (CGMCGM ≡ CGM² ) Survey combines HST-COS spectra of 22 z < 1 QSOs and Gemini GMOS spectra of hundreds of galaxies per QSO field to study the properties of gaseous halos surrounding galaxies. We present initial results from the survey, including GMOS spectroscopy of over 1000 galaxies in the foreground of the QSOs. Working with new python-based packages focused on quasar absorption spectroscopic analysis, pyigm and veeper, we are assessing the composition, kinematics and spatial extent of the CGM and its connection to host galaxy properties. Current and future work for the undergraduate-led component of this large survey includes assembling a database of galaxy ISM gas-phase oxygen abundances, emission-line-based star-formation rates, and Voigt-profile fitting of associated CGM absorbers. Ultimately, the comprehensive galaxy-absorber catalogs produced by this study are five times larger than all previous low-redshift samples combined and cover an epoch that has never before been systematically surveyed, offering new insights into the nature of the cosmic baryon cycle.