Stellar mass versus velocity dispersion as tracer of the lensing signal
  around bulge-dominated galaxies
  We present the results of a weak gravitational lensing analysis to determine
whether the stellar mass or the velocity dispersion is more closely related to
the amplitude of the lensing signal around galaxies - and hence to the
projected distribution of dark matter. The lensing signal on scales smaller
than the virial radius corresponds most closely to the lensing velocity
dispersion in the case of a singular isothermal profile, but is on larger
scales also sensitive to the clustering of the haloes. We select over 4000 lens
galaxies at a redshift z<0.2 with concentrated (or bulge-dominated) surface
brightness profiles from the ~300 square degree overlap between the
Red-sequence Cluster Survey 2 (RCS2) and the data release 7 (DR7) of the Sloan
Digital Sky Survey (SDSS). We consider both the spectroscopic velocity
dispersion and a model velocity dispersion (a combination of the stellar mass,
the size and the Sersic index of a galaxy). Comparing the model and
spectroscopic velocity dispersion we find that they correlate well for galaxies
with concentrated brightness profiles. We find that the stellar mass and the
spectroscopic velocity dispersion trace the amplitude of the lensing signal on
small scales equally well. The model velocity dispersion, however, does
significantly worse. A possible explanation is that the halo properties that
determine the small-scale lensing signal - mainly the total mass - also depend
on the structural parameters of galaxies, such as the effective radius and
Sersic index, but we lack data for a definitive conclusion.
