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 fNL 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 fNL/k². We first constrain fNL 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 fNL=171_-139⁺¹⁴⁰ at 68% C.L. and -69<fNL<+492 at 95% C.L. We discuss the degeneracies between fNL and other cosmological parameters. Including SN-Ia data and priors on H₀ from Hubble Space Telescope observations we find a stronger bound: -35<fNL<+479 at 95%. We also fit the more recent SDSS DR7 halo power spectrum data finding, for a ΛCDM+fNL model, fNL=-93±128 at 68% C.L. and -327<fNL<+177 at 95% C.L. We finally forecast the constraints on fNL from future surveys as EUCLID and from CMB missions as Planck showing that their combined analysis could detect fNL~5.