Detection of a Multiphase Intragroup Medium: Results from the COS-IGrM Survey

Abstract

Abstract We present the results of the Cosmic Origins Spectrograph-Intragroup Medium (COS-IGrM) Survey that used the COS on the Hubble Space Telescope to observe a sample of 18 UV bright quasars, each probing the IGrM of a galaxy group. We detect Lyα, C ii, N v, Si ii, Si iii, and O vi in multiple sightlines. The highest ionization species detected in our data is O vi, which was detected in eight out of 18 quasar sightlines. The wide range of ionization states observed provide evidence that the IGrM is patchy and multiphase. We find that the O vi detections generally align with radiatively cooling gas between 105.8 and 106 K. The lack of O vi detections in 10 of the 18 groups illustrates that O vi may not be the ideal tracer of the volume filling component of the IGrM. Instead, it either exists at trace levels in a hot IGrM or is generated in the boundary between the hotter IGrM and cooler gas.