Stellar mass distribution in M31 is estimated using optical and infrared
imaging data. Combining the derived stellar mass model with various kinematical
data, properties of the DM halo of the galaxy are constrained.
SDSS observations through the ugriz filters and the Spitzer imaging at 3.6
microns are used to sample the SED of the galaxy at each imaging pixel.
Intrinsic dust extinction effects are taken into account by using far-infrared
observations. Synthetic SEDs created with different stellar population
synthesis models are fitted to the observed SEDs, providing estimates for the
stellar mass surface density. The stellar mass distribution of the galaxy is
described with a 3D model consisting of a nucleus, a bulge, a disc, a young
disc and a halo component, each following the Einasto density distribution
(relations between different functional forms of the Einasto density
distribution are given in App. B). By comparing the stellar mass distribution
to the observed rotation curve and kinematics of outer globular clusters and
satellite galaxies, the DM halo parameters are estimated.
Stellar population synthesis models suggest that M31 is dominated by old
stars throughout the galaxy. The total stellar mass is (10-15)10^10Msun, 30% of
which is in the bulge and 56% in the disc. None of the tested DM distribution
models can be falsified on the basis of the stellar matter distribution and the
rotation curve of the galaxy. The virial mass of the DM halo is
(0.8-1.1)10^12Msun and the virial radius is 189-213kpc, depending on the DM
distribution. The central density of the DM halo is comparable to that of
nearby dwarf galaxies, low-surface-brightness galaxies and distant massive disc
galaxies, thus the evolution of central DM halo properties seems to be
regulated by similar processes for a broad range of halo masses, environments,
and cosmological epochs.Comment: 11 pages, 13 figures, 6 tables, accepted for publication in Astronomy
and Astrophysic
