Alpha-element enhancement in a LCDM Universe

Abstract

Abstract. We study the chemical enrichment of elliptical galaxies using a semi-analytic model of galaxy formation combined with a cosmological Nbody simulation of dark matter particles. In particular, we study the α-element abundances with respect to the iron content of galaxies. The main modification to the previous models (Cora 2006; Lagos et al. 2008; Tecce et al. 2010) was the implementation of a top heavy variable initial mass function with a theoretical basis (Weidner & Kroupa 2004, 2005, 2006; Weidner et al. 2011). We find that with a single initial mass function at all epochs the observed trend of [Alpha/Fe] with the stellar mass of elliptical galaxies can be hardly reproduced. We propound that a top heavy integrated galactic mass function can be a plausible solution for this problem.