Clustering of photometric luminous red galaxies I : Growth of Structure
  and Baryon Acoustic Feature
  The possibility of measuring redshift space (RSD) distortions using
photometric data have been recently highlighted. This effect complements and
significantly alters the detectability of baryon acoustic oscillations (BAO) in
photometric surveys. In this paper we present measurements of the angular
correlation function of luminous red galaxies (LRGs) in the photometric catalog
of the final data release (DR7) of the Sloan Digital Sky Survey II (SDSS). The
sample compromise ~ 1.5 x 10^6 LRGs distributed in 0.45 < z < 0.65, with a
characteristic photometric error of ~ 0.05. Our measured correlation centered
at z=0.55 is in very good agreement with predictions from standard LCDM in a
broad range of angular scales, $0.5^\circ < \theta < 6^\circ$. We find that the
growth of structure can indeed be robustly measured, with errors matching
expectations. The velocity growth rate is recovered as $f \sigma_8 = 0.53 \pm
0.42$ when no prior is imposed on the growth factor and the background geometry
follows a LCDM model with WMAP7+SNIa priors. This is compatible with the
corresponding General Relativity (GR) prediction $f \sigma_8 = 0.45$ for our
fiducial cosmology. If we adopt a parametrization such that $f=\Omega
^\gamma_m(z)$, with $\gamma \approx 0.55$ in GR, and combine our $f\sigma_8$
measurement with the corresponding ones from spectroscopic LRGs at lower
redshifts we obtain $\gamma=0.54 \pm 0.17$. In addition we find evidence for
the presence of the baryon acoustic feature matching the amplitude, location
and shape of LCDM predictions. The photometric BAO feature is detected with 98
% confidence level at z=0.55.
