Galaxy groups in the 2dF Galaxy Redshift Survey: a compactness analysis of groups

ARIEL ZANDIVAREZ; MARIANO DOMINGUEZ; CINTHIA RAGONE-FIGUEROA; HERNÁN MURIEL; HECTOR J. MARTINEZ

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Blackwell Synergy - Royal Astronomical Society

Lugar: Londres, Reino Unido; Año: 2003 vol. 340 p. 1400 - 1408

0035-8711

A comprehensive study on compactness has been carried out on the 2dF Galaxy Group Catalogue constructed by Merchán and Zandivarez. The compactness indices defined in this work take into account different geometrical constraints in order to explore a wide range of possibilities. Our results show that there is no clear distinction between groups with high and low levels of compactness when considering particular properties such as the radial velocity dispersion, the relative fraction of galaxies per spectral type, and the luminosity functions of their galaxy members. Studying the trend of the fraction of galaxies per spectral type as a function of the dimensionless crossing time, some signs of dynamical evolution are observed. From the comparison with previous works on compactness, we realize that special care should be taken for some compactness criteria definitions in order to avoid possible biases in the identification.