  We present a measurement of mass estimates for dark matter halos around
galaxies from the COMBO-17 survey using weak gravitational lensing. COMBO-17 is
particularly useful for this kind of investigation because it covers
observations in 17 optical filters from which accurate photometric redshifts
and spectral classification for objects with $R<24$ are derived. This allows us
to select lens and source galaxies from their redshifts and to thus avoid any
uncertainties from estimates of the source redshift distribution. We study
galaxy lenses at redshifts $z_\mathrm{d}=0.2-0.7$ by fitting the normalization
of either singular isothermal spheres (SIS) or Navarro-Frenk-White (NFW)
profiles to the whole lens sample; we then consider halos around blue and red
subsamples separately. We also constrain the scaling of halo mass with light.
For the NFW model, we find virial masses
$M_\mathrm{vir}^*=3.9^{+3.3}_{-2.4}\times 10^{11}h^{-1}M_{\sun}$ (1-$\sigma$)
for blue and $M_\mathrm{vir}^*=7.1^{+7.1}_{-3.8}\times 10^{11}h^{-1}M_{\sun}$
for red galaxies of $L_\star=10^{10}h^{-2}L_{\sun}$, respectively. The derived
mass-to-light scaling relations suggest that the mass-to-light ratio might
decrease with increasing luminosity for blue galaxies but increase with
increasing luminosity for red galaxies. However, these differences between blue
and red galaxies are only marginally significant and both subsamples are
consistent with having the same mass-to-light ratio at all luminosities.
Finally, we compare our results to those obtained from the Red-Sequence Cluster
Survey (RCS) and the Sloan Digital Sky Survey (SDSS). Taking differences in the
actual modelling into account, we find very good agreement with these surveys.
