3D spectroscopy of dwarf elliptical galaxies

TL;DR

This study uses 3D spectroscopy to analyze dwarf elliptical galaxies, revealing that they have younger, metal-rich cores and older, metal-poor outer regions, suggesting nuclear starbursts influence their stellar populations.

Contribution

It provides new insights into the stellar population gradients of dwarf ellipticals, highlighting the role of nuclear starbursts in their evolution, contrasting with previous downsizing interpretations.

Findings

Cores are 2-4 Gyr old with super-solar metallicities.

Outer regions are older than 12 Gyr with subsolar metallicities.

Nuclear starbursts may explain age-mass correlations in ellipticals.

Abstract

I present some results of 3D spectroscopy for a small sample of dwarf elliptical galaxies, mostly members of small groups. The galaxies under consideration have a typical absolute magnitude of -18 (B-band), and at the Kormendy's relation they settle within a transition zone between the main cloud of giant ellipticals and the sequence of diffuse ellipticals. By measuring Lick indices and investigating radial profiles of the SSP-equivalent ages and metallicities of the stellar populations in their central parts, I have found evolutionary distinct cores in all of them. Typically, the ages of these cores are 2-4 Gyr, and the metallicities are higher than the solar one. Outside the cores, the stellar populations are always old, T>12 Gyr, and the metallicities are subsolar. This finding implies that the well-known correlation between the stellar age and the total mass (luminosity) of field ellipticals (Trager et al. 2000, Caldwell et al. 2003, Howell 2005) may be in fact a direct consequence of a larger contribution of nuclear starbursts into the integrated stellar population in dwarfs with respect to giants, and does not relate to `downsizing'.