Abstract

The circumgalactic medium (CGM) is host to large reservoirs of gas around galaxies, potentially on its way to becoming the fuel for galactic star formation. As gas flows from the intergalactic medium (IGM) and on into the CGM, we should be able to detect it as cold gas accretion. Much of this cold gas is too diffuse for easy detection, however if a telescope stares far enough and long enough, we should be able to see it. I will be focusing on recent results from our program to map the CGM of 18 galaxies in the MHONGOOSE survey in neutral hydrogen (HI) with the Green Bank Telescope. For this program we obtained deep observations with high HI column density sensitivity, and focused on the diffuse HI detected outside the disks of each galaxy. By quantifying the fraction of diffuse HI in the CGM, we were able to look for correlations with other properties of the galaxies, such as the baryonic and halo masses. We also analyzed each map as a function of radius, creating column density and cumulative flux profiles for each galaxy in our sample. Most galaxies showed an increasing cumulative flux profile at large radii, suggesting that either an HI truncation radius was not reached, or that we are seeing the large-scale diffuse structure from the IGM.