Browsing by Author "February, S"

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    Cosmological model dependence of the galaxy luminosity function: far-infrared results in the Lemaître-Tolman-Bondi model
    (2013) Iribarrem, A; Andreani, P; Gruppioni, C; February, S; Ribeiro, M B; Berta, S; Le Floc’h, E; Magnelli, B; Nordon, R; Popesso, P; Pozzi, F; Riguccini, L
    Aims. This is the first paper of a series aiming at investigating galaxy formation and evolution in the giant-void class of the Lemaître-Tolman-Bondi (LTB) models that best fits current cosmological observations. Here we investigate the luminosity function (LF) methodology, and how its estimates would be affected by a change on the cosmological model assumed in its computation. Are the current observational constraints on the allowed cosmology enough to yield robust LF results?
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    Evolution of linear perturbations in spherically symmetric dust spacetimes
    (IOP Publishing, 2014-08-13) February, S; Larena, J; Clarkson, C; Pollney, D
    We present results from a numerical code implementing a new method to solve the master equations describing the evolution of linear perturbations in a spherically symmetric but inhomogeneous background. This method can be used to simulate several configurations of physical interest, such as relativistic corrections to structure formation, the lensing of gravitational waves (GWs) and the evolution of perturbations in a cosmological void model. This paper focuses on the latter problem, i.e. structure formation in a Hubble scale void in the linear regime. This is considerably more complicated than linear perturbations of a homogeneous and isotropic background because the inhomogeneous background leads to coupling between density perturbations and rotational modes of the spacetime geometry, as well as GWs. Previous analyses of this problem ignored this coupling in the hope that the approximation does not affect the overall dynamics of structure formation in such models. We show that for a giga-parsec void, the evolution of the density contrast is well approximated by the previously studied decoupled evolution only for very large-scale modes. However, the evolution of the gravitational potentials within the void is inaccurate at more than the 10% level, and is even worse on small scales.
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    Relativistic cosmology number densities in void-Lemaître-Tolman-Bondi models
    (2014) Iribarrem, A; Andreani, P; February, S; Gruppioni, C; Lopes, A R; Ribeiro, M B; Stoeger, W R
    Aims. The goal of this work is to compute the number density of far-IR selected galaxies in the comoving frame and along the past lightcone of observationally constrained Lemaître-Tolman-Bondi “giant void” models and to compare those results with their standard model counterparts.