Formation et Evolution des Galaxies - Groupe de Recherche IAP

Date	Sujet	Présenté par
5 mars 2009	Environment and mass dependencies of galactic spin parameter: comparison of cosmological simulations with observed galaxies We use a sample of galaxies from the Sloan Digital Sky Survey (SDSS) to search for correlations between the lambda spin parameter and the environment and mass of galaxies. In order to calculate the total value of lambda for each observed galaxy, we employed a simple model of the dynamical structure of the galaxies, which allows a rough estimate of the value of lambda using only readily obtainable observables from the luminous galaxies. Use of a large volume-limited sample (upwards of 11,000) allows reliable inferences of mean values and dispersions of lambda distributions. We find, in agreement with some N-body cosmological simulations, no significant dependence of lambda on the environmental density of the galaxies. For the case of mass, our results show a marked correlation with lambda, in the sense that low-mass galaxies present both higher mean values of lambda and associated dispersions, than high-mass galaxies. These results provide interesting constrain on the mechanisms of galaxy formation and acquisition of angular momentum, a valuable test for cosmological models. 0607605 0712.0842 0802.3689	Xavier Hernandez Doring UNAM, Mexico