Misc,

Radial variations in the stellar initial mass function of early-type galaxies

, , , , and .
(2014)cite arxiv:1404.6533Comment: 13 pages, 10 figures. Submitted to MNRAS.

Abstract

The hypothesis of a universal initial mass function (IMF) -- motivated by observations in nearby stellar systems -- has been recently challenged by the discovery of an IMF systematic variation with the central velocity dispersion, \sigma, of early-type galaxies (ETGs), towards an excess of low-mass stars in high \sigma galaxies. This trend has been found to hold for the central regions of ETGs, and remains unexplained at the present. To shed new lights on it, we have obtained new, extremely deep, spectroscopy, for three nearby ETGs, two with high \sigma (~300 km/s), and one low-mass system, with \sigma ~ 100 km/s. From the analysis of IMF-sensitive spectral features, we find that the IMF depends significantly on galactocentric distance in the massive ETGs, with the enhanced fraction of low-mass stars confined to their central regions. For the low-\sigma galaxy, no significant radial gradient is detected in the IMF, which is well described by a Milky-Way-like distribution at all radii. Such a result suggests that the IMF should be regarded as a local (rather than global) galaxy property, and suggests a significant difference in the formation process of the core and the outskirts of massive galaxies.

Tags

Users

  • @miki

Comments and Reviews