Galaxy-galaxy lensing constraints on the relation between baryons and
  dark matter in galaxies in the Red Sequence Cluster Survey 2
  We present the results of a study of weak gravitational lensing by galaxies
using imaging data that were obtained as part of the second Red Sequence
Cluster Survey (RCS2). In order to compare to the baryonic properties of the
lenses we focus here on the ~300 square degrees that overlap with the DR7 of
the SDSS. The depth and image quality of the RCS2 enables us to significantly
improve upon earlier work for luminous galaxies at z>=0.3. Comparison with
dynamical masses from the SDSS shows a good correlation with the lensing mass
for early-type galaxies. For low luminosity (stellar mass) early-type galaxies
we find a satellite fraction of ~40% which rapidly decreases to <10% with
increasing luminosity (stellar mass). The satellite fraction of the late-types
has a value in the range 0-15%. We find that early-types in the range
10^10<L_r<10^11.5 Lsun have virial masses that are about five times higher than
those of late-type galaxies and that the mass scales as M_200 \propto L^2.34
+0.09 \ -0.16. We also measure the virial mass-to-light ratio, and find for
L_200<10^11 Lsun a value of M_200/L_200=42+-10 for early-types, which increases
for higher luminosities to values that are consistent with those observed for
groups and clusters of galaxies. For late-type galaxies we find a lower value
of M_200/L_200=17+-9. Our measurements also show that early- and late-type
galaxies have comparable halo masses for stellar masses M_*<10^11 Msun, whereas
the virial masses of early-type galaxies are higher for higher stellar masses.
Finally, we determine the efficiency with which baryons have been converted
into stars. Our results for early-type galaxies suggest a variation in
efficiency with a minimum of ~10% for a stellar mass M_*,200=10^12 Msun. The
results for the late-type galaxies are not well constrained, but do suggest a
larger value. (abridged)
