Stephane Courteau

Title: The Luminosity Profile of the Andromeda Galaxy

Abstract: We present an extended light profile for the Andromeda
galaxy and decompose it into three basic luminous structural
components: a bulge, a disk and a halo.  Our data set covers
the radial range from the nucleus all the way to the stellar
halo at 200 kpc.  We apply, and address the limitations of,
different decomposition methods for 1D light profiles and
2D images.  Despite model covariances, the convergence of
solutions based on different methods suggests a stable set
of final structural parameters.  Among others, the bulge
follows not a de Vaucouleurs profile but rather a Sersic
profile with n=2.2+/-.3.  This result suggests a first rapid
formation of the bulge via mergers followed by secular growth
from the disk.  The halo has a 2D power-law index (-2.3)
comparable to that of the Milky Way.  If M31 and the Milky Way
are at all typical, faint stellar halos should soon be routinely
detected in galaxy surveys that reach below mu_i < 27 mag arcsec^{-2}