Cosmological parameter constraints from galaxy-galaxy lensing and galaxy
  clustering with the SDSS DR7
  Recent studies have shown that the cross-correlation coefficient between
galaxies and dark matter is very close to unity on scales outside a few virial
radii of galaxy halos, independent of the details of how galaxies populate dark
matter halos. This finding makes it possible to determine the dark matter
clustering from measurements of galaxy-galaxy weak lensing and galaxy
clustering. We present new cosmological parameter constraints based on
large-scale measurements of spectroscopic galaxy samples from the Sloan Digital
Sky Survey (SDSS) Data Release 7 (DR7). We generalise the approach of Baldauf
et al. (2010) to remove small scale information (below 2 and 4 Mpc/h for
lensing and clustering measurements, respectively), where the cross-correlation
coefficient differs from unity. We derive constraints for three galaxy samples
covering 7131 sq. deg., containing 69150, 62150, and 35088 galaxies with mean
redshifts of 0.11, 0.28, and 0.40. We clearly detect scale-dependent galaxy
bias for the more luminous galaxy samples, at a level consistent with
theoretical expectations. When we vary both \sigma_8 and \Omega_m (and
marginalise over non-linear galaxy bias) in a flat LCDM model, the
best-constrained quantity is \sigma_8 (\Omega_m/0.25)^{0.57}=0.80 +/- 0.05
(1-sigma, stat. + sys.), where statistical and systematic errors have
comparable contributions, and we fixed n_s=0.96 and h=0.7. These strong
constraints on the matter clustering suggest that this method is competitive
with cosmic shear in current data, while having very complementary and in some
ways less serious systematics. We therefore expect that this method will play a
prominent role in future weak lensing surveys. When we combine these data with
WMAP7 CMB data, constraints on \sigma_8, \Omega_m, H_0, w_{de} and \sum m_{\nu}
become 30--80 per cent tighter than with CMB data alone, since our data break
several parameter degeneracies.
