Sanskriti Das: A deep search for missing accretion in the circumgalactic medium

The circumgalactic HI might hold the clue to the missing accretion: the mismatch between the HI accretion rate and star formation rate of local (z~0) galaxies. If it traces the neutral fraction of a predominantly ionized CGM, it could also host missing galactic baryons. Using the Green Bank Telescope, we probed the 21-cm emission from HI in the CGM of several local galaxies out to 100 kpc impact parameter at an unprecedented sensitivity of 1e16 cm^-2. We detected HI of diverse spectral shapes, kinematic properties, and column densities. Interferometric maps from the Westerbork Synthesis Radio Telescope cannot explain more than 50% of these single-dish detections. This excess circumgalactic HI along major axes pointings co-rotate with the HI disks and is an inflow/fountain along the minor axes pointings. Whether it accounts for the missing baryons and missing accretion is subject to individual targets.