Galaxy distribution and evolution around a sample of 2dF groups

Abstract

Context. We study galaxy evolution and spatial patterns in the surroundings of a sample of 2dF groups. Aims. Our aim is to find evidence of galaxy evolution and clustering out to 10 times the virial radius of the groups and so redefine their properties according to the spatial patterns in the fields and relate them to galaxy evolution. Methods. Group members and interlopers were redefined after the identification of gaps in the redshift distribution. We then used exploratory spatial statistics based on the the second moment of the Ripley function to probe the anisotropy in the galaxy distribution around the groups. Results. We found an important anticorrelation between anisotropy around groups and the fraction of early-type galaxies in these fields. Our results illustrate how the dynamical state of galaxy groups can be ascertained by the systematic study of their neighborhoods. This is an important achievement, since the correct estimate of the extent to which galaxies are affected by the group environment and follow large-scale filamentary structure is relevant to understanding the process of galaxy clustering and evolution in the Universe.

Segregation effects according to the evolutionary stage of galaxy groups

“…To determine the group redshift, only galaxies within 0.50 h −1 Mpc are considered. Details about this procedure are found in Lopes et al (2009); see also Ribeiro et al (2009) for applications of this technique to 2dF galaxy groups. With the new redshift and velocity limits, we apply an algorithm for interloper rejection to define the final list of group members.…”

Non-Gaussian velocity distributions — the effect on virial mass estimates of galaxy groups

“…The idea of working with such large areas is to probe the effect of secondary infall onto groups. Members and interlopers were redefined after the identification of gaps in the redshift distribution according to the technique described by Lopes et al (2009). Finally, a virial analysis is perfomed to estimate the groups' properties.…”

“…Ribeiro, P.A.A. Lopes and M. Trevisan gaps in the redshift distribution according to the technique described by Lopes et al (2009). Finally, a virial analysis is perfomed to estimate the groups' properties.…”

Formação e evolução de galáxias: populações estelares na Via Láctea, galáxias elípticas e propriedades de galáxias em grupos

“…Details about this procedure are found in Lopes et al (009a); see also Ribeiro et al (2009) for applications of this technique to 2dF galaxy groups. With the new redshift and velocity limits, we apply an algorithm for interloper rejection to define the final list of group members.…”

“…Finally, a virial analysis is perfomed to estimate the groups' properties. See details in Lopes et al (009b), Ribeiro et al (2009), andRibeiro et al (2010). We have classified the groups after applying the AD test to their galaxy velocity distributions (see Hou et al, 2009, for a good description of the test).…”