Constraints on primordial non-Gaussianity from WMAP7 and luminous red galaxies power spectrum and forecast for future surveys

We place new constraints on the primordial local non-Gaussianity parameter f(NL) using recent cosmic microwave background anisotropy and galaxy clustering data. We model the galaxy power spectrum according to the halo model, accounting for a scale-dependent bias correction proportional to f(NL)/k(2). We first constrain f(NL) in a full 13 parameters analysis that includes 5 parameters of the halo model and 7 cosmological parameters. Using the WMAP7 CMB data and the SDSS DR4 galaxy power spectrum, we find f(NL) = 171(-139)(+140) at 68% C.L. and -69 < f(NL) < +492 at 95% C.L. We discuss the degeneracies between f(NL) and other cosmological parameters. Including SN-Ia data and priors on H-0 from Hubble Space Telescope observations we find a stronger bound: -35 < f(NL) < +479 at 95%. We also fit the more recent SDSS DR7 halo power spectrum data finding, for a Lambda CDM + f(NL) model, f(NL) = -93 +/- 128 at 68% C.L. and -327 < f(NL) < +177 at 95% C.L. We finally forecast the constraints on f(NL) from future surveys as EUCLID and from CMB missions as Planck showing that their combined analysis could detect f(NL) similar to 5.