Galaxy satellites, building blocks and the hierarchical clustering paradigm

PADILLA, N.; LAGOS, C. DEL P.; CORA, S. A.

La Plata

Congreso; LII Reunión Anual de la Asociación Argentina de Astronomía; 2009

We study the properties of building blocks (BBs, i.e. accreted satellites) and surviving satellites of present-day galaxies using a semi-analytic model of galaxy formation in the context of a concordance Lambda Cold Dark Matter cosmology. We consider large numbers of dark-matter (DM) halo merger trees spanning a wide range of masses(1×1010 to 2.14×1014Msun). Our simulated galaxies show higher metallicities for BBs with respect to surviving satellites, an effect produced bythe same processes responsible for the build-up of the mass-metallicity relation. We prove that these metallicity differences arise from the higher peak in the density fluctuation field occupied by BBs and central galaxies which have collapsed into a single object earlier than surviving satellites. BBs start to form stars earlier, during the peak of the merger activity in the universe, and build up half of their final stellar mass (measured at the moment of disruption) up to four times faster than surviving satellites. Surviving satellites keep increasing their stellar masses rather quiescently from their formation until z = 1. The difference between the metallicities of satellites, BBs and central galaxies depends on the host DM halo mass, in a way that can be used as a further test for the concordance cosmology.