Grupos de galaxias en el catálogo 2dF: La estructura en gran escala con grupos

ZANDIVAREZ, A.; MERCHÁN, M. E.; PADILLA, N. D.

La Plata, Buenos Aires

Congreso; Reunion de la Asociación Argentina de Astronomía; 2003

Asociación Argentina de Astronomía

We use the 2dF Galaxy Group Catalogue constructed by Merchán & Zandivarez to study the large scale structure of the Universe traced by galaxy groups. The resulting group power spectrum shows a similar shape to the galaxy power spectrum of the 2dF Galaxy Redshift Survey, but with a higher amplitude quantified by a relative bias in redshift space of bs(k) ∼ 1.5. The group two point correlation function ξ(s) for the total sample is well described by a power law with correlation length s0=8.9 ± 0.3 h-1 Mpc and slope γ=-1.6 ± 0.1. In order to study the dependence of the clustering properties on group mass we split the catalogue in four subsamples defined by different ranges of group virial masses finding that our results are consistent with a 40% increase of the correlation length s0. These computations allow a fair estimate of the relation described by s0 and the mean intergroup separation dc. An empirical scaling law s0=4.7 dc0.32 provides a very good fit to the results from this work, as well as to previous results obtained for groups and clusters of galaxies and for dark matter haloes in N-body simulations of ΛCDM models. We also study the redshift space distortions of galaxy groups, finding that the anisotropies in the clustering pattern of groups are consistent with gravitational instability, with a flattening of the ξ(s) contours in the direction of the line of sight and group pairwise velocities found for almost the whole sample of groups are consistent with < w2 >1/2 = (280+50-110)km/s, in agreement with ΛCDM cosmological simulations. The bias factor for the 2dF groups of moderate masses is consistent with the values predicted by the combination of a CDM model and the ellipsoidal collapse model for the formation of structures.