Speaker
Dr
Jorge Penarrubia
(IoA, University of Cambridge)
Description
Dwarf spheroidal galaxies (dSphs) are the most dark matter(DM) dominated and densest
galaxies in the known Universe. As such they provide interesting cases for indirect
DM detection experiments. Unfortunately, deriving the distribution of DM in dSphs is
severely hampered by the strong degeneracy that exists between the stellar velocity
anisotropy and enclosed DM mass. Here I will present a new method for measuring the
slopes of mass profiles within dSphs directly from stellar spectroscopic data and
without adopting a particular DM halo model. This method combines two recent results:
1) spherically symmetric, equilibrium Jeans models imply that the product of
half-light radius and (squared) stellar velocity dispersion provides an accurate
estimate of the mass enclosed within the stellar half-light radius and 2) some dSphs
have chemo-dynamically distinct stellar subcomponents that independently trace the
same gravitational potential. Our method uses measurements of stellar positions,
velocities and spectral indices of individual stars to statistically estimate the
half-light radii and velocity dispersions of both subcomponents. For a dSph with two
detected stellar
subcomponents, this procedure yields estimates of masses enclosed at two discrete
points in the same mass profile, immediately defining a slope. I will present
preliminary results for two dSphs that show spatially and kinematically distinct
stellar populations: Fornax and Sculptor.
Primary author
Dr
Jorge Penarrubia
(IoA, University of Cambridge)
Co-author
Dr
Matt Walker
(Cfa, Harvard)
