paper

Type Ia supernovae and the formation history of early-type galaxies

arXiv:astro-ph/0207632 · doi:10.1046/j.1365-8711.2002.05863.x

Abstract

Using the standard prescription for the rates of supernovae type II and type Ia, we compare the predictions of a simple model of star formation in galaxies with the observed radial gradients of abundance ratios in a sample of early-type galaxies to infer the relative contribution of each type of supernova. The data suggests a correlation between the fractional contribution of Type Ia to the chemical enrichment of the stellar populations (1-xi) and central velocity dispersion of order 1-xi ~ -0.16log sigma_0+0.40, so that the type Ia contribution in stars ranges from a negligible amount in massive galaxies up to 10% in low-mass systems. Our model is parametrized by a star formation timescale (t_SF) which controls the duration of the starburst. A correlation with galaxy radius as a power law (t_SF ~ r^beta) translates into a radial gradient of the abundance ratios. The data implies a wide range of formation scenarios for a simple model that fixes the luminosity profile, ranging from inside-out (beta=2), to outside-in formation (beta=-1), as is consistent with numerical simulations of elliptical galaxy formation. An alternative scenario that links t_SF to the dynamical timescale favours inside-out formation over a smaller range. In both cases, massive galaxies are predicted to have undergone a more extended period of star formation in the outer regions with respect to their low-mass counterparts.

Accepted for publication in MNRAS. 8 pages with 5 embedded color EPS figures

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