Crazy heart: kinematics of the “star pile” in Abell 545⋆
Departamento de AstronomíaUniversidad de Concepción,
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2 European Southern Observatory, Alonso de Córdova 3107, Santiago, Chile
3 UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA
4 Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH, UK
5 Argelander Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
Accepted: 31 January 2011
We study the structure and internal kinematics of the “star pile” in Abell 545 – a low surface brightness structure lying in the center of the cluster. We have obtained deep long-slit spectroscopy of the star pile using VLT/FORS2 and Gemini/GMOS, which is analyzed in conjunction with deep multiband CFHT/MEGACAM imaging. As presented in a previous study the star pile has a flat luminosity profile and its color is consistent with the outer parts of elliptical galaxies. Its velocity map is irregular, with parts being seemingly associated with an embedded nucleus, and others which have significant velocity offsets to the cluster systemic velocity with no clear kinematical connection to any of the surrounding galaxies. This would make the star pile a dynamically defined stellar intra-cluster component. The complicated pattern in velocity and velocity dispersions casts doubts on the adequacy of using the whole star pile as a dynamical test for the innermost dark matter profile of the cluster. This status is fulfilled only by the nucleus and its nearest surroundings which lie at the center of the cluster velocity distribution.
Key words: galaxies: clusters: individual: Abell 545 / galaxies: kinematics and dynamics / galaxies: halos / galaxies: interactions
Based on observations taken at the European Southern Observatory, Cerro Paranal, Chile, under programme ID 080.B-0529. Also based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Sscience and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and SECYT (Argentina); and on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii.
© ESO, 2011