06/05/2009 – 14h – Auditório Principal, Bloco G – IAG/USP

Robert Proctor

IAG/USP

Título/Title: Probing the 2-D kinematic structure of early-type galaxies out to 3 effective radii

Resumo/Abstract:

I will detail an innovative new technique for measuring the 2-D velocity moments (rotation velocity, velocity dispersion and Gauss-Hermite coefficients h3 and h4) of the stellar populations of galaxy halos using spectra from Keck DEIMOS multi-object spectroscopic observations. The data are used to reconstruct 2-D rotation velocity maps. I will present data for five nearby early-type galaxies to ~3 effective radii. These provide significant insights into the global kinematic structure of the galaxies, and challenge the accepted morphological classification in several cases. I will show that between 1 and 3 effective radii the velocity dispersion4 declines very slowly, if at all, in all five galaxies. For the two galaxies with velocity dispersion profiles available from planetary nebulae data we find very good agreement with our stellar profiles. We find a variety of rotation profiles beyond 1 effective radius, i.e rotation speed remaining constant, decreasing AND increasing with radius. These results are of particular importance to studies which attempt to classify galaxies by their kinematic structure within one effective radius, such as the recent definition of fast- and slow- rotator classes by the SAURON project. The data suggests that the rotator class may change when larger galacto-centric radii are probed. This has important implications for dynamical modeling of early-type galaxies.

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