Using N-body+hydro simulations we study relations between the local
environments of galaxies on 0.5 Mpc scale and properties of the luminous
components of galaxies. Our numerical simulations include effects of star
formation and supernova feedback in different cosmological scenarios: the
standard Cold Dark Matter model, the Broken Scale Invariance model (BSI), and a
model with cosmological constant (LCDM).
In this paper, we concentrate on the effects of environment on colors and
morphologies of galaxies, on the star formation rate and on the relation
between the total luminosity of a galaxy and its circular velocity. We
demonstrate a statistically significant theoretical relationship between
morphology and environment. In particular, there is a strong tendency for
high-mass galaxies and for elliptical galaxies to form in denser environments,
in agreement with observations. We find that in models with denser environments
(CDM scenario) ~ 13 % of the galactic halos can be identified as field
ellipticals, according to their colors. In simulations with less clustering
(BSI and LCDM), the fraction of ellipticals is considerably lower (~ 2-3 %).
The strong sensitivity of morphological type to environment is rather
remarkable because our results are applicable to ``field'' galaxies and small
groups. If all galaxies in our simulations are included, we find a
statistically significant dependence of the galaxy luminosity - circular
velocity relation on dark matter overdensity within spheres of radius 0.5 Mpc,
for the CDM simulations. But if we remove ``elliptical'' galaxies from our
analysis to mimic the Tully-Fisher relation for spirals, then no dependence is
found in any model.Comment: 44 pages, 21 figures (17 included). Submitted to New Astronomy. GIFF
color plots and the complete paper in Postscript (including color figures)
can be found at http://astrosg.ft.uam.es/~gustavo/newas
