Dark and luminous matter connections. Towards understanding galaxy evolution

Abstract

In this review we outline the major points of ab-initio cosmological models focusing on some galaxy evolution unresolved problems. In particular our knowledge of the star formation rate which leads galaxy evolution, i.e. luminosity, colors and dust enrichment, is still very poor. Smoothed particle hydrodynamic simulations including chemo-photometric evolutionary population synthesis models of isolated collapsing systems endowed with triaxial dark matter halos, gas and the star formation switched on, are a useful tool to shed light on several open questions. This approach, which allows a greater particle resolution than a fully consistent cosmological scenario, gives us important insights into connections between dark and luminous matter. Both the initial properties of the halo, as so as its geometry and dynamical state, and total mass of the system, drive the galaxy formation and evolution. In our simple framework spiral galaxies arise only in systems with both a total mass less than 1.e12 solar masses and a critical value of the baryonic-to-total-mass ratio, around its cosmological value, 0.1. For the same value of such a ratio more massive systems host more luminous and redder galaxies, as a consequence of the stronger burst of star formation arising into their halos earlier on. Moreover the star formation does not switch on in the less massive DM halos so that the critical mass to entail a luminous system is 1.e11 solar masses. For a given total mass, higher values of the baryonic-to-total-mass ratio provide galaxies with lower rotational support so that no constraints to the total mass of the system hosting an elliptical galaxy have been derived.