Reinabelle Reyes, Rachel Mandelbaum, James E. Gunn, Reiko Nakajima, Uros Seljak, Chris M. Hirata
In this paper, we measure the virial-to-optical velocity ratios V_vir/V_opt
of disk galaxies in the Sloan Digital Sky Survey (SDSS) at a mean redshift of
= 0.07 and with stellar masses 10^9 M_sun < M_* < 10^11 M_sun. V_vir/V_opt,
the ratio of the circular velocity measured at the virial radius of the dark
matter halo (~150 kpc) to that at the optical radius of the disk (~10 kpc), is
a powerful observational constraint on disk galaxy formation. It links galaxies
to their dark matter haloes dynamically and constrains the total mass profile
of disk galaxies over an order of magnitude in length scale. For this
measurement, we combine V_vir derived from halo masses measured with
galaxy-galaxy lensing, with V_opt derived from the Tully-Fisher relation (TFR)
from Reyes et al. (2011). In anticipation of this combination, we use
similarly-selected galaxy samples for both the lensing and TFR analysis. For
three M_* bins with lensing-weighted mean stellar masses of 0.6, 2.7, and 6.5 x
10^10 M_sun, we find halo-to-stellar mass ratios M_vir/M_* = 41, 23, and 26,
with 1-sigma statistical uncertainties of around 0.1 dex, and V_vir/V_opt=0.79,
0.72, and 0.79 (or V_opt/V_vir of approximately 1.3), with 1-sigma statistical
uncertainties of around 0.05 in V_vir/V_opt, respectively. Our results suggest
that the dark matter and baryonic contributions to the mass within the optical
radius are comparable, if the dark matter halo profile has not been
significantly modified by baryons. The results obtained in this work will serve
as inputs to and constraints on disk galaxy formation models, which will be
explored in future work. Finally, we note that this paper presents a new and
improved galaxy shape catalogue for weak lensing that covers the full SDSS DR7
footprint.
View original:
http://arxiv.org/abs/1110.4107
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