Kinematics of MgII Absorbers from the Redshift-space Distortion Around
  Massive Quiescent Galaxies
  The kinematics of MgII absorbers is the key to understanding the origin of
cool, metal-enriched gas clouds in the circumgalactic medium of massive
quiescent galaxies. Exploiting the fact that the cloud line-of-sight velocity
distribution is the only unknown for predicting the redshift-space
distortion~(RSD) of MgII absorbers from their 3D real-space distribution around
galaxies, we develop a novel method to infer the cool cloud kinematics from the
redshift-space galaxy-cloud cross-correlation $\xi^{s}$. We measure $\xi^{s}$
for ${\sim}10^4$ MgII absorbers around ${\sim}8{\times}10^5$ CMASS galaxies at
$0.4{<}z{<}0.8$. We discover that $\xi^{s}$ does not exhibit a strong
Fingers-of-God effect, but is heavily truncated at velocity ${\sim}300\,km/s$.
We reconstruct both the redshift and real-space cloud number density
distributions inside haloes, $\xi^{s}_{1h}$ and $\xi_{1h}$, respectively. Thus,
for any model of cloud kinematics, we can predict $\xi^{s}_{1h}$ from the
reconstructed $\xi_{1h}$, and self-consistently compare to the observed
$\xi^{s}_{1h}$. We consider four types of cloud kinematics, including an
isothermal model with a single velocity dispersion, a satellite infall model in
which cool clouds reside in the subhaloes, a cloud accretion model in which
clouds follow the cosmic gas accretion, and a tired wind model in which clouds
originate from the galactic wind-driven bubbles. All the four models provide
statistically good fits to the RSD data, but only the tired wind model can
reproduce the observed truncation by propagating ancient wind bubbles at
${\sim}250\,km/s$ on scales ${\sim}400\,kpc/h$. Our method provides an exciting
path to decoding the dynamical origin of metal absorbers from the RSD
measurements with upcoming spectroscopic surveys.
