Velocity Dispersions of Massive Quiescent Galaxies from Weak Lensing and
  Spectroscopy
  We use MMT spectroscopy and deep Subaru Hyper Suprime-Cam (HSC) imaging to
compare the spectroscopic central stellar velocity dispersion of quiescent
galaxies with the effective dispersion of the dark matter halo derived from the
stacked lensing signal. The spectroscopic survey (the Smithsonian Hectospec
Lensing Survey) provides a sample of 4585 quiescent galaxy lenses with measured
line-of-sight central stellar velocity dispersion ($\sigma_{\rm SHELS}$) that
is more than 85% complete for $R < 20.6$, $D_{n}4000> 1.5$ and $M_{\star} >
10^{9.5}{\rm M}_{\odot}$. The median redshift of the sample of lenses is 0.32.
We measure the stacked lensing signal from the HSC deep imaging. The central
stellar velocity dispersion is directly proportional to the velocity dispersion
derived from the lensing $\sigma_{\rm Lens}$, $\sigma_{\rm Lens} =
(1.05\pm0.15)\sigma_{\rm SHELS}+(-21.17\pm35.19)$. The independent
spectroscopic and weak lensing velocity dispersions probe different scales,
$\sim3$kpc and $\gtrsim$ 100 kpc, respectively, and strongly indicate that the
observable central stellar velocity dispersion for quiescent galaxies is a good
proxy for the velocity dispersion of the dark matter halo. We thus demonstrate
the power of combining high-quality imaging and spectroscopy to shed light on
the connection between galaxies and their dark matter halos.
