TheB‐Band Luminosity Function of Red and Blue Galaxies up toz= 3.5

Abstract

We have explored the redshift evolution of the luminosity function of red and blue galaxies up to z ¼ 3:5. This was possible by joining a deep I-band composite galaxy sample, which includes the spectroscopic K20 sample and the Hubble Deep Field samples, with the deep H AB ¼ 26 and K AB ¼ 25 samples derived from the deep NIR images of the Hubble Deep Field-North and Hubble Deep Field-South, respectively. About 30% of the sample has spectroscopic redshifts and the remaining fraction well-calibrated photometric redshifts. This allowed us to select and measure galaxies in the rest-frame blue magnitude up to z $ 3 and derive the redshift evolution of the B-band luminosity function of galaxies separated by their rest-frame U À V color or specific (i.e., per unit mass) star formation rate. The class separation was derived from passive evolutionary tracks or from their observed bimodal distributions. Both distributions appear bimodal at least up to z $ 2, and the locus of red/early galaxies is clearly identified up to these high redshifts. Both luminosity and density evolutions are needed to describe the cosmological behavior of the red/early and blue/late populations. The density evolution is greater for the early population with a decrease by 1 order of magnitude at z $ 2 3 with respect to the value at z $ 0:4. The luminosity densities of the early-and late-type galaxies with M B < À20:6 appear to have a bifurcation at z > 1. Indeed, while star-forming galaxies slightly increase or keep constant their luminosity density, ''early'' galaxies decrease in their luminosity density by a factor of $5-6 from z $ 0:4 to z $ 2:5 3. A comparison of one of the latest versions of the hierarchical cold dark matter models shows a broad agreement with the observed number and luminosity density evolutions of both populations.

A new (2+1)D cluster finding algorithm based on photometric redshifts: large scale structure in the Chandra deep field south

“…-Our results add new evidence in favour of constant slope of the C-M relation in clusters, at least up to z = 1 implying a constant mass-metallicity relation, according to the standard interpretations. -Our analysis shows that the average C-M relation for galaxies belonging to the red population is consistent with a linear extrapolation of the relation found by Bell et al (2004) up to z = 1.5, complementing the results of Giallongo et al (2005), who have shown that the blueing of the average colour of the red galaxies extends to z ≈ 2−3.…”

“…This assumption is justified by the analysis of Blakeslee et al (2003) who find a constant slope for different galaxy clusters up to z = 1.2 (see the next paragraph). At higher redshifts Giallongo et al (2005) find a decrease of the red sequence slope ∂(U −V) rest /∂M B rest from −0.098 to −0.062, in the two wide redshift bins 0.4-1 and 1.3-3.5 respectively. In the present analysis, which is limited to z < 1.7, we neglect this change of slope and we estimate the red sequence colours in three relatively narrow redshift bins.…”

“…Field objects were uniformly distributed on a square of 6 × 6 arcmin centred on the cluster, with a space density and absolute magnitude distributions assigned according to the redshift-dependent Schechter-like (Schechter 1976) LF derived by Giallongo et al (2005):…”

“…Alternatively it is possible to fit the observed SED with either empirical (Lanzetta et al 1996) or theoretical templates (Giallongo et al 1998). Photometric redshifts have been successfully used to trace the evolution in cosmic time of the average galaxy population (Poli et al 2003;Giallongo et al 2005). However, the present accuracy of photometric redshifts leaves no room for standard FOF methods.…”

GMASS ultradeep spectroscopy of galaxies at z ~ 2

“…A bimodality in galaxy colours up to z ∼ 2 was also found by Cassata et al (2008) in the GMASS field and Giallongo et al (2005) in the HDF. The latter also showed that the blue and red galaxy populations most probably had different evolutionary histories.…”