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synthesis of a kinematically distinct core

By G. K. T. Hau, D. Carter and M. Balcells

Abstract

We report on the discovery of a rapidly co-rotating stellar and gas component in the nucleus of the shell elliptical NGC 2865. The stellar component extends ∼ 0.51h −1 100 kpc along the major axis, and shows depressed velocity dispersion and absorption line profiles skewed in the opposite sense to the mean velocity. Associated with it is a young stellar population with enhanced Hβ, lowered Mg and same Fe indices relative to the underlying elliptical. Its recent star formation history is constrained by considering “bulge+burst ” models under 4 physically motivated scenarios, using evolutionary population synthesis. Scenarios in which the nuclear component is formed over a Hubble time or recently from continuous gas inflow are ruled out. A recent starburst can satisfy observational constraints only if its population has metallicity 2.5–6.3 times that of the bulge. The nuclear iron to magnesium index ratio can be explained by a temperature effect in the atmospheres of stars at main sequence turnoffs between A3 and F4, during which the Fe indices of the burst population ar

Year: 2008
OAI identifier: oai:CiteSeerX.psu:10.1.1.317.5988
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