Optical and near-infrared velocity dispersions of early-type galaxies
  We have carried out a systematic, homogeneous comparison of optical and
near-infrared dispersions. Our magnitude-limited sample of early-type galaxies
in the Fornax cluster comprises 11 elliptical and 11 lenticular galaxies more
luminous than MB = -17. We were able to determine the central dispersions based
on the near-infrared CO absorption band head for 19 of those galaxies. The
velocity dispersions range from less than 70 km/s to over 400 km/s. We compare
our near-infrared velocity dispersions to the optical dispersions measured by
Kuntschner (2000). Contrary to previous studies, we find a one-to-one
correspondence with a median fractional difference of 6.4%. We examine the
correlation between the relative dust mass and the fractional difference of the
velocity dispersions, but find no significant trend. Our results suggest that
early-type galaxies are largely optically thin, which is consistent with recent
Herschel observations.
