Identifying Bright Stars in Crowded Environments Using Velocity
  Dispersion Measurements, and an Application to the Center of M32
  The identification of individual stars in crowded environments using
photometric information alone is confounded by source confusion. However, with
the addition of spectroscopic information it is possible to distinguish between
blends and areas where the light is dominated by a single star using the widths
of absorption features. We describe a procedure for identifying locations in
kinematically hot environments where the light is dominated by a single star,
and apply this method to spectra with 0.1 arcsec angular resolution covering
the 2.1 - 2.3 micron interval in the central regions of M32. Targets for
detailed investigation are selected as areas of localized brightness
enhancement. Three locations where at least 60% of the K-band light comes from
a single bright star, and another with light that is dominated by two stars
with very different velocities, are identified. The dominant stars are evolving
near the tip of the asymptotic giant branch (AGB), and have M5 III spectral
type. The lack of a dispersion in spectral-type suggests that the upper AGB
within the central arcsec of M32 has a dispersion in J-K of only a few
hundreths of a magnitude, in agreement with what is seen at larger radii. One
star has weaker atomic absorption lines than the others, such that [M/H] is 0.2
dex lower. Such a difference in metallicity is consistent with the metallicity
dispersion inferred from the width of the AGB in M32. The use of line width to
distinguish between blends involving many relatively faint stars, none of which
dominate the light output, and areas that are dominated by a single
intrinsically bright star could be extended to crowded environments in other
nearby galaxies.
