A faint extended cluster in the outskirts of NGC 5128: evidence of a low mass accretion
We report the discovery of an extended globular cluster in a halo field in Centaurus A (NGC 5128), situated from the centre of that galaxy, imaged with the Advanced Camera for Surveys on board the Hubble Space Telescope. At the distance of the galaxy, the half-light radius of the cluster is rh∼ 17 p...
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Published in | Monthly notices of the Royal Astronomical Society Vol. 404; no. 3; pp. 1157 - 1164 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Oxford, UK
Blackwell Publishing Ltd
21.05.2010
Wiley-Blackwell Oxford University Press |
Subjects | |
Online Access | Get full text |
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Summary: | We report the discovery of an extended globular cluster in a halo field in Centaurus A (NGC 5128), situated from the centre of that galaxy, imaged with the Advanced Camera for Surveys on board the Hubble Space Telescope. At the distance of the galaxy, the half-light radius of the cluster is rh∼ 17 pc, placing it among the largest globular clusters known. The faint absolute magnitude of the star cluster, MV,○=−5.2, and its large size render this object somewhat different from the population of extended globular clusters previously reported, making it the first firm detection in the outskirts of a giant galaxy of an analogue of the faint, diffuse globular clusters present in the outer halo of the Milky Way. The colour–magnitude diagram of the cluster, covering approximately the brightest four magnitudes of the red giant branch, is consistent with an ancient, i.e. ≳8 Gyr, intermediate metallicity, i.e. [M/H]∼−1.0 dex, stellar population. We also report the detection of a second, even fainter cluster candidate which would have rh∼ 9 pc and MV,○=−3.4 if it is at the distance of NGC 5128. The properties of the extended globular cluster and the diffuse stellar populations in its close vicinity suggest that they are part of a low mass accretion in the outer regions of NGC 5128. |
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Bibliography: | istex:21E956B0CA5C3AD84C5E6C608854A763EB26F8D1 This work was based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. ark:/67375/HXZ-H82G9GQM-2 Hubble Space Telescope This work was based on observations with the NASA/ESA obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5‐26555. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0035-8711 1365-2966 |
DOI: | 10.1111/j.1365-2966.2010.16363.x |