Galaxy groups in the 2dF Galaxy Redshift Survey: luminosity and mass statistics (original) (raw)

The Galaxy Cosmological Mass Function

This paper studies the galaxy cosmological mass function (GCMF) in a semi-empirical relativistic approach which uses observational data provided by recent galaxy redshift surveys. Starting from a relation presented by Ribeiro & Stoeger (2003) between the mass-to-light ratio, the selection function obtained from the luminosity function (LF) data and the luminosity density, the average luminosity L* and the average galactic mass Mg are computed in terms of the redshift. Mg is also alternatively estimated by means of a method that uses the galaxy stellar mass function (GSMF). Comparison of these two forms of deriving the average galactic mass allows us to infer a possible bias introduced by the selection criteria of the survey. We used the FORS Deep Field galaxy survey sample of 5558 galaxies in the redshift range 0.5<z<5.0 and its LF Schechter parameters in the B-band, as well as this sample’s stellar mass-to-light ratio and its GSMF data. Assuming Mg ≈ 10^11 M⊙ as the local value of the average galactic mass, the LF approach results in L_B ∝ (1+z)^(2.40±0.03) and Mg ∝ (1+z)^(1.1±0.2). However, using the GSMF results to calculate the average galactic mass produces Mg ∝ (1+z)^(−0.58±0.22). We chose the latter result as it is less biased. We then obtain ed the theoretical quantities of interest, such as the differential number counts, etc, to finally calculate the GCMF, which can be fitted by a Schechter function, but whose fitted parameter values are different from the ones found in the literature for the GSMF. This GCMF behavior follows the theoretical predictions from the cold dark matter models in which the less massive objects form first, being followed later by more massive ones. In the range 0.5<z<2.0 the GCMF has a strong variation that can be interpreted as a higher rate of galaxy mergers or as a strong evolution in the star formation formation history of these galaxies.