Old Massive Globular Clusters and the Stellar Halo of the Dwarf
  Starburst Galaxy NGC 4449
  We use Hubble Space Telescope imaging to show that the nearby dwarf starburst
galaxy NGC 4449 has an unusual abundance of luminous red star clusters. Joint
constraints from integrated photometry, low-resolution spectroscopy, dynamical
mass-to-light ratios, and resolved color-magnitude diagrams provide evidence
that some of these clusters are old globular clusters. Spectroscopic data for
two massive clusters suggest intermediate metallicities ([Fe/H] ~ -1) and
subsolar Mg enhancement ([Mg/Fe] ~ -0.1 to -0.2). One of these clusters may be
the nucleus of a tidally disrupting dwarf galaxy; the other is very massive (~
3 x 10^6 M_sun). We have also identified a population of remote halo globular
clusters. NGC 4449 is consistent with an emerging picture of the ubiquity of
stellar halos among dwarf galaxies, and study of its globular clusters may help
distinguish between accretion and in situ scenarios for such halos.
