Weak lensing measurements of dark matter halos of galaxies from COMBO-17

Received / Accepted Abstract. 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 zd = 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 � vir = 3.9