Schedule Feb 17, 2012
Alpha-element Abundances in a LCDM Universe
Ignacio Gargiulo (IALP), Sofía Alejandra Cora (IALP), Nelson Padilla (PUC)

We study the chemical enrichment of galaxies using a semi-analytic model of galaxy formation (Cora 2006; Lagos et al. 2008; Tecce et al. 2010), that is combined with a cosmological N-body simulation of dark matter particles. In particular, we track the alpha-element abundances with respect of the iron content of galaxies. Our aim is to find solutions for two different intriguing trends that are difficult to explain in a build-up scenario of galaxy formation:

(i) the [α/Fe]-Mass relation for elliptical galaxies, that shows an increase in the [α/Fe] ratio for more massive galaxies (larger velocity dispersion σ), and

(ii) the enhancement of alpha-elements in the Milky Way stellar halo with respect to the corresponding abundances in their satellite galaxies.

In order to adress the second we use a simple model for the formation of stellar haloes that considers tidal stripping just before each merger event occurs. Regarding the first problem we found that with a single initial mass function at all epochs the observed trend of [α/Fe] with the stellar mass of elliptical galaxies can be hardly reproduced. We propound a top heavy integrated galactic Initial Mass Function (Weidner et al. 2011) as a plausible solution for this problem.


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