The globular cluster systems of Abell 1185^⋆

¹ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
e-mail: mwest@eso.org
² Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
e-mail: ajordan@astro.puc.cl
³ Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V9E 2E7, Canada
e-mail: john.blakeslee@nrc-cnrc.gc.ca; patrick.cote@nrc-cnrc.gc.ca
⁴ Institute for Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, L-413, Livermore, CA 94550, USA
e-mail: gregg@igpp.ucllnl.org
⁵ Department of Physics, University of California, Davis, CA 956160, USA
e-mail: gregg@igpp.ucllnl.org
⁶ Department of Physics and Astronomy, University of Hawaii, Hilo, HI 96720, USA
e-mail: mtakamiya@hawaii.edu
⁷ Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132-4163, USA
e-mail: marzke@stars.sfsu.edu

Received: 15 October 2010
Accepted: 26 January 2011

Abstract

We examine the properties of a previously discovered population of globular clusters in the heart of the rich galaxy cluster Abell 1185 that might be intergalactic in nature. Deep images obtained with the Advanced Camera for Surveys (ACS) aboard Hubble Space Telescope (HST) confirm the presence of  ~1300 globular clusters brighter than I_F814W ≃ 27.3 mag in a field devoid of any large galaxies. The luminosities and colors of these objects are found to be similar to those of metal-poor globular clusters observed in many galaxies to date. Although a significant fraction of the detected globular clusters undoubtedly reside in the outer halos of galaxies adjacent to this field, detailed modeling of their distribution suggests that the majority of these objects are likely to be intergalactic, in the sense that they are not gravitationally bound to any individual galaxy. We conclude that the true nature and origin of the globular cluster population in the core of A1185  −  galactic residents or intergalactic wanderers  −  remains uncertain, and suggest how future observation could resolve this ambiguity.