Description
Author and Speaker: Isabelle Goldstein
Abstract: The stellar kinematics in dwarf galaxies can provide a wealth of information about its underlying dark matter distribution. Line of sight velocity dispersion measurements from six classical dwarf galaxies can be used to show that axion-like particles with masses of order m ~ 10−22 eV are inconsistent with the potential distribution in classical dwarf galaxies unless the hierarchical assembly of the Milky Way did not trace the mean evolution of Milky Way size halos. However, line of sight velocity constraints alone are subject to degeneracies between central dark matter density and stellar velocity anisotropy.
Using Gaia DR3 data, we examine the kinematics of the central core of the Sagittarius (Sgr) dwarf spheroidal galaxy which includes proper motions and line-of-sight velocities for member stars in addition to their projected positions. We extract a sample of bright stars that are high-probability members of Sgr. We obtain a velocity anisotropy of βa=−2.24±1.99, which implies a system with tangentially-biased orbits. Proper motions and complete position information could be used to break the existing velocity anisotropy and central density degeneracy; however without accurate distances to these stars, a 6D Jeans analysis cannot be performed. We use new observations obtained with the Magellan/MIKE spectrograph to measure distances and line-of-sight velocities for RR Lyrae and red clump stars with the Sgr core to perform a full 6D Jeans analysis.
