  Using the Hubble Space Telescope, we have resolved individual red-giant
branch stars in the halos of eight nearby spiral galaxies. The fields lie at
projected distances between 2 and 13 kpc along the galaxies' minor axes. The
data set allows a first look at the systematic trends in halo stellar
populations. We have found that bright galaxies tend to have broad red-giant
branch star color distributions with redder mean colors, suggesting that the
heavy element abundance spread increases with the parent galaxy luminosity. The
mean metallicity of the stellar halo, estimated using the mean colors of
red-giant branch stars, correlates with the parent galaxy luminosity. The
metallicity of the Milky Way halo falls nearly 1 dex below this
luminosity-metallicity relation, suggesting that the halo of the Galaxy is more
the exception than the rule for spiral galaxies; i.e., massive spirals with
metal-poor halos are unusual. The luminosity-halo stellar abundance relation is
consistent with the scaling relation expected for stellar systems embedded in
dominant halos, suggesting that the bulk of the halo stellar population may
have formed in situ.
