1205.1517 (O. Cucciati et al.)

Comparison of the VIMOS-VLT Deep Survey with the Munich semi-analytical model. II. The colour-density relation up to z=1.5    [PDF]

O. Cucciati, G. De Lucia, E. Zucca, A. Iovino, S. de la Torre, L. Pozzetti, J. Blaizot, G. Zamorani, M. Bolzonella, D. Vergani, S. Bardelli, L. Tresse, A. Pollo

[Abridged] We perform on galaxy mock catalogues the same colour-density (C-D) analysis made by Cucciati et al. (2006) on a 5 Mpc/h scale using the VVDS-Deep survey, and compare the results from mocks with observed data. We use mock catalogues with the same flux limits (I=24) as the VVDS (CMOCKS), built using the semi-analytic model by De Lucia & Blaizot (2007) applied to the Millennium Simulation. From CMOCKS, we extracted samples of galaxies mimicking the VVDS observational strategy (OMOCKS). We computed the B-band Luminosity Function LF and the C-D relation in the mocks. We find that the LF in mocks roughly agrees with the observed LF, but at z<0.8 the faint-end slope of the model LF is steeper than the VVDS one. Computing the LF for early and late type galaxies, we show that mocks have an excess of faint early-type and of bright late-type galaxies with respect to data. We find that the C-D relation in OMOCKS is in excellent agreement with the one in CMOCKS. At z~0.7, the C-D relation in mocks agrees with the VVDS one (red galaxies reside mainly in high densities). Yet, the strength of the C-D relation in mocks does not vary within 0.21.5, and/or that galaxy colour is affected by environment on scales <5 Mpc/h, and this is not mirrored on larger scales. The reversal of the C-D relation can be explained by wet mergers between young galaxies, producing a starburst event. This should be seen on group scales. A residual of this is found in observations at z=1.5 on larger scales (5 Mpc/h), but not in the mocks, suggesting that the treatment of environmental processes in models should be revised.

View original: http://arxiv.org/abs/1205.1517