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

Abstract

We present the results of the COS Intragroup Medium (COS-IGrM) Survey that used the Cosmic Origins Spectrograph on the Hubble Space Telescope to observe a sample of 18 UV bright quasars, each probing the intragroup medium (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 8 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 10 5.8 and 10 6 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.

A Complex Multiphase DLA Associated with a Compact Group at z=2.431 Traces Accretion, Outflows, and Tidal Streams

“…Further characterising the kinematics of Mg systems in loose groups, Nielsen et al (2018) found more optical depth at higher velocity than in isolated systems, possibly a signature of an intragroup medium (IGrM) or the interactions between galaxies. A similar enhancement for small loose groups was found in C (Burchett et al 2016) but O instead becomes weaker with lower covering fractions (Pointon et al 2017;Ng et al 2019;McCabe et al 2021;although Tchernyshyov et al 2021 found larger covering fractions for galaxies with neighbours and column densities log(𝑁 (O )/cm −2 ) < 14.1). To better understand the origin of these enhancements and complex kinematics, Hamanowicz et al (2020) suggested kinematically connecting the absorption components along the line-of-sight to each galaxy in the group.…”