Volume 520, September-October 2010
|Number of page(s)||5|
|Published online||30 September 2010|
Letter to the Editor
Max-Plank-Institut für Extraterrestrische Physik,
Giessenbachstraße 1, 85741 Garching bei München, Germany e-mail: email@example.com
2 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
3 INAF, Osservatorio Astronomico di Pino Torinese, 10025 Pino Torinese, Italy
Accepted: 10 September 2010
Context. An important open question is the relation between intracluster light and the halos of central galaxies in galaxy clusters.
Aims. Here we report results from an on going project with the aim to characterize the dynamical state in the core of the Hydra I (Abell 1060) cluster around NGC 3311.
Methods. We analyze deep long-slit absorption line spectra reaching out to ~25 kpc in the halo of NGC 3311.
Results. We find a very steep increase in the velocity dispersion profile from a central σ0 = 150 km s-1 to σout 450 km s-1 at R 12 kpc. Farther out, to ~25 kpc, σ appears to be constant at this value, which is ~60% of the velocity dispersion of the Hydra I galaxies. With its dynamically hot halo kinematics, NGC 3311 is unlike other normal early-type galaxies.
Conclusions. These results and the large amount of dark matter inferred from X-rays around NGC 3311 suggest that the stellar halo of this galaxy is dominated by the central intracluster stars of the cluster, and that the transition from predominantly galaxy-bound stars to cluster stars occurs in the radial range 4 to 12 kpc from the center of NGC 3311. We comment on the wide range of halo kinematics observed in cluster central galaxies, depending on the evolutionary state of their host clusters.
Key words: galaxies: clusters: general / galaxies: clusters: individual: Hydra I / galaxies: kinematics and dynamics / galaxies: individual: NGC 3311
Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, during the observing program 082.A-0255(A) on 2009 March 25.
Table 1 is only available in electronic form at http://www.aanda.org
© ESO, 2010
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