BRANCHINI , Enzo Franco

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In the framework of indirect dark matter searches we investigate the flux of high energy gamma-ray photons produced by annihilation of dark matter in caustics within our Galaxy under the hypothesis that the bulk of dark matter is composed of the lightest supersymmetric particles. Unfortunately, the detection of the caustic annihilation signal...

Starting from the observed distribution of Abell/ACO galaxy clusters in redshift space, we use a two-step procedure to recover their distances and peculiar velocities. After statistically correcting for the unobserved cluster distribution in the zone of avoidance and also for a smooth absorption at higher latitudes, we use a dynamical iterative...

The least action principle (LAP) is a dynamically rigorous method for deriving the history of galaxy orbits. In particular it is an Omega test, predicting current epoch galaxy velocities as a function of position and of the cosmological background. It is most usefully applied to in-falling structures, such as the local group, where its...

Under the hypothesis of a dark matter composed by supersymmetric particles such as neutralinos, we investigate the possibility that their annihilation in the halos of nearby galaxies could produce detectable fluxes of gamma photons. Expected fluxes depend on several, poorly known quantities such as the density profiles of dark matter halos, the...

Given the present distribution of mass tracing objects in an expanding universe, we develop and test a fast method for recovering their past orbits using the least action principle. In this method, termed FAM for fast action minimization, the orbits are expanded in a set of orthogonal time basis functions satisfying the appropriate boundary...

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There is an ~150 km s-1 discrepancy between the measured motion of the Local Group (LG) of galaxies with respect to the cosmic microwave background and the linear theory prediction based on the gravitational force field of the large-scale structure in full-sky redshift surveys. We perform a variety of tests which show that the LG motion cannot...

We present a simple method for evaluating the nonlinear biasing function of galaxies from a redshift survey. The nonlinear biasing is characterized by the conditional mean of the galaxy density fluctuation given the underlying mass density fluctuation , or by the associated parameters of mean biasing, (b) over cap, and nonlinearity, (b) over...

Spatial variations in the distribution of galaxy luminosities, estimated from redshifts as distance proxies, are correlated with the peculiar velocity field. Comparing these variations with the peculiar velocities inferred from galaxy redshift surveys is a powerful test of gravity and dark-energy theories on cosmological scales. Using ~2 ×105...

The cosmological peculiar velocity field (deviations from the pure Hubble flow) of matter carries significant information on dark energy, dark matter and the underlying theory of gravity on large scales. Peculiar motions of galaxies introduce systematic deviations between the observed galaxy redshifts z and the corresponding cosmological...

Upcoming γ-ray satellites will search for Dark Matter (DM) annihilations in Milky Way substructures (or `clumps'). The prospects for detecting these objects strongly depend on the assumptions made on the distribution of DM in substructures, and on the distribution of substructures in the Milky Way halo. By adopting simplified, yet rather...

The B-band and near-infrared (H) luminosity functions of spiral galaxies are derived for the Coma and A1367 clusters and for a reference population of ''field'' galaxies in the Coma supercluster. They are consistent at the bright end, but they differ significantly at the faint end, indicating an overdensity of spirals with blue color (B-H <...

We present extensive tests of the fast action method (FAM) for recovering the past orbits of mass tracers in an expanding universe from their redshift-space coordinates at the present epoch. The tests focus on the reconstruction of present-day peculiar velocities using mock catalogues extracted from high-resolution N-body simulations. The...

We show how, based on considerations on the observed form of the galaxy two-point spatial correlation function xi(r), a very simplified-yet surprisingly effective-model for the linear density fluctuations power spectrum can be constructed. We first relate the observed large-scale shape of xi(r) to a power-law form for the power spectrum, P(k)...

Observed galaxy luminosities (derived from redshifts) hold information on the large-scale peculiar velocity field in the form of spatially correlated scatter, which allows for bounds on bulk flows and the growth rate of matter density perturbations using large galaxy redshift surveys. We apply this luminosity approach to galaxies from the...

Spatial modulations in the distribution of observed luminosities (computed using redshifts) of ~ 5 × 105 galaxies from the SDSS Data Release 7, probe the cosmic peculiar velocity field out to z ~ 0.1. Allowing for luminosity evolution, the r-band luminosity function, determined via a spline-based estimator, is well represented by a Schechter...

Given a redshift survey of galaxies with measurements of apparent magnitudes, we present a novel method for measuring the growth rate f(Omega) of cosmological linear perturbations. We use the galaxy distribution within the survey to solve for the peculiar velocity field which depends in linear perturbation theory on beta = f (Omega)/b, where b...

We present a simple method for measuring cosmological bulk flows from large redshift surveys, based on the apparent dimming or brightening of galaxies due to their peculiar motion. It is aimed at estimating bulk flows of cosmological volumes containing large numbers of galaxies. Constraints on the bulk flow are obtained by minimizing systematic...

Using the nearly full-sky Ks= 11.75 2MASS Redshift Survey (2MRS; Huchra et al.) of ˜45 000 galaxies, we reconstruct the underlying peculiar velocity field and constrain the cosmological bulk flow within ˜100 h-1 Mpc. These results are obtained by maximizing the probability to estimate the absolute magnitude of a galaxy given its observed...

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We use high-resolution hydrodynamical simulations to investigate the spatial correlation between weak (N(H) (I) < 10(15) cm(-2)) Ly alpha absorbers and gas-rich galaxies in the local Universe. We confirm that Ly alpha absorbers are preferentially expected near gas-rich galaxies and that the degree of correlation increases with the column...

Many experiments in the near future will test dark energy through its effects on the linear growth of matter perturbations. In this paper, we discuss the constraints that future large-scale redshift surveys can put on three different parametrizations of the linear growth factor and how these constraints will help ruling out different classes of...

We constructed a Bayesian hyper-parameter statistical method to quantify the difference between predicted velocities derived from the observed galaxy distribution in the IRAS-PSCz (Point Source Catalogue Redshift) survey and peculiar velocities measured using different distance indicators. In our analysis, we find that the model-data comparison...