http://dspace-roma3.caspur.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-05-18T10:53:34Z http://hdl.handle.net/2307/225 <Title>Primordial non-Gaussianities in the intergalactic medium</Title> <Authors>Viel, Matteo; Branchini, Enzo; Dolag, Klaus; Grossi, Margherita; Matarrese, Sabino; Moscardini, Lauro</Authors> <Issue Date>2009</Issue Date> <Is part of>Monthly notices of the Royal Astronomical Society</Is part of> <Volume>393</Volume> <Pages>774-782</Pages> <Abstract>We present results from the first high-resolution hydrodynamical simulations of non-Gaussian cosmological models. We focus on the statistical properties of the transmitted Lyman-alpha flux in the high-redshift intergalactic medium. Imprints of non-Gaussianity are present and are larger at high redshifts. Differences larger than 20 per cent at z > 3 in the flux probability distribution function for high-transmissivity regions (voids) are expected for values of the non-linearity parameter f(NL) = +/- 100 when compared to a standard Lambda cold dark matter cosmology with f(NL) = 0. We also investigate the one-dimensional flux bispectrum: at the largest scales(corresponding to tens of Mpc), we expect deviations in the flux bispectrum up to 20 per cent at z similar to 4 (for f(NL) = +/- 100),significantly larger than deviations of similar to 3 per cent in the flux power spectrum. We briefly discuss possible systematic errors that can contaminate the signal. Although challenging, a detection of non-Gaussianities in the interesting regime of scales and redshifts probed by the Lyman-alpha forest could be possible with future data sets.</Abstract> 2008-12-31T23:00:00Z http://hdl.handle.net/2307/263 <Title>Large-scale non-Gaussian mass function and halo bias: tests on N-body simulations</Title> <Authors>Grossi, Margherita; Verde, Licia; Carbone, Carmelita; Dolag, Klaus; Branchini, Enzo; Iannuzzi, Francesca; Matarrese, Sabino; Moscardini, Lauro</Authors> <Issue Date>2009</Issue Date> <Is part of>Monthly Notices of the Royal Astronomical Society</Is part of> <Volume>398</Volume> <Pages>321-332</Pages> <Abstract>The description of the abundance and clustering of haloes for non-Gaussian initial conditions has recently received renewed interest,motivated by the forthcoming large galaxy and cluster surveys, which can potentially yield constraints of the order of unity on the non-Gaussianity parameter f(NL). We present tests on N-body simulations of analytical formulae describing the halo abundance and clustering for non-Gaussian initial conditions. We calibrate the analytic non-Gaussian mass function of Matarrese, Verde & Jimenez and LoVerde et al. and the analytic description of clustering of haloes for non-Gaussian initial conditions on N-body simulations. We find an excellent agreement between the simulations and the analytic predictions if we make the corrections delta(c) -> delta(c)root q and delta(c) -> delta(c)q, where q similar or equal to 0.75, in the density threshold for gravitational collapse and in the non-Gaussian fractional correction to the halo bias, respectively. We discuss the implications of this correction on present and forecasted primordial non-Gaussianity constraints. We confirm that the non-Gaussian halo bias offers a robust and highly competitive test of primordial non-Gaussianity.</Abstract> 2008-12-31T23:00:00Z