The circumgalactic medium of eBOSS emission line galaxies: signatures of
  galactic outflows in gas distribution and kinematics
  We study the distribution and kinematics of the cool circumgalactic medium
(CGM) of emission line galaxies (ELGs) traced by metal absorption lines. Using
about 200,000 ELGs from SDSS-IV eBOSS and half a million background quasars
from SDSS, we measure the median absorption strength of MgII and FeII lines in
quasar spectra for impact parameters ranging from 10 kpc to 1 Mpc. For
comparison we measure the same quantity around luminous red galaxies (LRGs). On
scales greater than 100 kpc both ELGs and LRGs exhibit similar absorption
profiles. However, metal absorption is 5-10 times stronger around ELGs on
smaller scales. The metal absorption strength is anisotropic, with an excess
along the minor-axis of the galaxies, indicating an outflow origin of the
absorbing gas. The ratio between the velocity dispersion of the cool CGM and
that of its host dark matter halo is about one for ELGs but about half for
LRGs. These results show that the dichotomy of galaxy types is reflected in
both the density distribution and kinematics of the CGM traced by metal
absorption lines. Our results provide strong evidence that the CGM of ELGs is
enriched by gas outflows generated by star formation.
