Johannes Zabl - Mini Workshop 3 October

Abstract: "A strong body of indirect observational evidence suggests that galaxies need to accrete gas from their surrounding medium. It is very much an ongoing challenge, though, to directly observe the accreting gas around individual galaxies.

Background quasars allow to probe the line-of-sight kinematics and physical properties of the gas surrounding intervening galaxies through the study of absorption lines. Since back-ground quasars do give the location of the gas, along with other key observables such as the gas column density, it is possible to put tight constraints on the mass flux of outflows and similarly for accretion depending on the galaxy orientation with respect to the quasar line-of-sight.

Unfortunately, background quasars are rare, and both the identification of galaxy-absorber pairs and the subsequent measurement of the galaxy orientation and kinematics are observationally expensive tasks, especially so at high redshifts. However, thanks to the MusE GAs FLOw and Wind [MEGAFLOW] survey, which is targeting 80+ galaxies associated to MgII systems at z=0.3-1.4 with the IFU spectrograph MUSE, we have a statistical sample of galaxy-absorber pairs to constrain the kinematics of the circumgalactic gas in an unprecedented way.

In this talk, I will focus on those galaxy-absorber pairs that we can identify as accretion cases. I will present the methodology and results with which we demonstrate the existence of predicted cold gas accretion-disks that are co-aligned and co-rotating with the associated galaxies. Further, I will demonstrate how we infer an approximate accretion rate and conclude that the inferred accretion rate is approximately consistent with self-regulating star formation.”