Asymmetric Drift in the Andromeda Galaxy (M31) as a Function of Stellar
  Age
  We analyze the kinematics of Andromeda's disk as a function of stellar age by
using photometry from the Panchromatic Hubble Andromeda Treasury (PHAT) survey
and spectroscopy from the Spectroscopic and Photometric Landscape of
Andromeda's Stellar Halo (SPLASH) survey. We use HI 21-cm and CO ($\rm J=1
\rightarrow 0$) data to examine the difference between the deprojected rotation
velocity of the gas and that of the stars. We divide the stars into four
stellar age bins, from shortest lived to longest lived: massive main sequence
stars (0.03 Gyr), more luminous intermediate mass asymptotic giant branch (AGB)
stars (0.4 Gyr), less luminous intermediate mass AGB stars (2 Gyr), and low
mass red giant branch stars (4 Gyr). There is a clear correlation between the
offset of the stellar and the gas rotation velocity, or the asymmetric drift:
the longer lived populations lag farther behind the gas than short lived
populations. We also examine possible causes of the substructure in the
rotation curves and find that the most significant cause of scatter in the
rotation curves comes from the tilted ring model being an imperfect way to
account for the multiple warps in Andromeda's disk.
