Kinematics of M31’s Thick Disk of Red Giant Stars

The Andromeda galaxy (M31) is the nearest galaxy to us that is larger than our own. It is an excellent test bed for the study of galaxy formation and evolution in our astronomical backyard. In this study, we use precise radial velocity measurements of several thousand red giant branch stars that were obtained via Keck DEIMOS spectroscopy as part of the Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo (SPLASH) survey. These kinematical data are coupled with high resolution images and multi-band photometry from the Hubble Space Telescope that were obtained as part of the Panchromatic Hubble Andromeda Treasury (PHAT) survey. We present the first detailed analysis of the kinematics of the thick stellar disk of M31. Our analysis takes into account of independent constraints on the spatial thickness of the disk obtained from PHAT studies of dust in M31’s disk.