16742

The observed growth in both the size and mass of galactic disks since redshift two requires an even larger increase in the specific angular momentum of the gas accreted from the circumgalactic medium comma which is the only reservoir of gas that can sustain disk star formation for 10 billion years. The rotation of inflowing circumgalactic gas is therefore central to the development of the angular momentum of stellar disks. Observing gas accretion is complicated by the galactic outflows that feedback from massive stars drive out of the galactic plane. While the position angle and axis ratio describe the projected shape of the galactic disk comma this leaves an ambiguity of which side of the galaxy minor axis tips toward the observer. This ambiguity produces degenerate solutions in modeling gas flows and identifying the origin of the observed gas comma because observers do not know where the gas lies along line-of-sight. We propose new WFC3-UVIS imaging observation to map the spiral structures of 11 z=0.25 galaxies with circumgalactic Mg II absorption detected in the quasar sightlines. We will determine the 3D disk orientation using rotation curves and the wrapping direction of galaxy spiral arms. The imaging sample will be combined with 3 Mg II absorbing galaxies with spiral arms detected in archival images comma bringing our sample to 14 galaxies. We collected high-resolution spectra of the quasars paired with the galaxies these spectra resolved multiple Mg II components. The 3D orientation will constrain parameters of physical models (disks comma radial inflow comma and conical outflow) in individual sightlines. The measured gas flow properties will provide new constraints for models of disk growth.