The Radio Universe at Low Surface Brightness: Feedback & accretion in
  the circumgalactic medium
  Massive galaxies at high-z are known to co-evolve with their circumgalactic
medium (CGM). If we want to truly understand the role of the CGM in the early
evolution of galaxies and galaxy-clusters, we need to fully explore the
multi-phase nature of the CGM. We present two novel science cases that utilize
low-surface-brightness observations in the radio regime to better understand
the CGM around distant galaxies. At the lowest temperatures, observations of
widespread molecular gas are providing evidence for the cold baryon cycle that
grows massive galaxies. At the highest temperatures, observations of the
Sunyaev-Zeldovich Effect are starting to reveal the effect of quasar feedback
onto the hot gas in the CGM. We discuss the critical role that radio
interferometers with compact configurations in the millimeter regime will play
over the next decade in understanding the crucial role of the multi-phase CGM
in galaxy evolution.
