The smooth MgII gas distribution through the interstellar/extra-planar/halo interface

We report the first measurements of MgII absorption systems associated with spectroscopically confirmed z ∼ 0.1 star-forming galaxies at projected distances of D < 6 kpc. We demonstrate the data are consistent with the well known anti-correlation between rest-frame MgII equivalent width, Wr(2796), and impact parameter, D, represented by a single log-linear relation derived by Nielsen et al. (MAGIICAT) that converges to ∼ 2 Å at D = 0 kpc. Incorporating MAGIICAT, we find that the halo gas covering fraction is unity below D ∼ 25 kpc. We also report that our r D < 6 kpc absorbers are consistent with the Wr(2796) distributions of the Milky Way interstellar medium (ISM) and ISM+halo. In addition, quasar sight-lines of intermediate redshift galaxies with 6 < D < 25 kpc have an equivalent width distribution similar to that of the Milky Way halo, implying that beyond ∼ 6 kpc, quasar sight-lines are likely probing halo gas and not the ISM. As inferred by the Milky Way and our new data, the gas profiles of galaxies can be fit by a single log-linear Wr(2796) - D relation out to large scales across a variety of gas-phase conditions and is maintained through the halo/extra-planar/ISM interfaces, which is remarkable considering their kinematic complexity. These low redshift, small impact parameter absorption systems are the first steps to bridge the gap between quasar absorption-line studies and HI observations of the circumgalactic medium.