2010MNRAS.404.1157M -
Mon. Not. R. Astron. Soc., 404, 1157-1164 (2010/May-3)
A faint extended cluster in the outskirts of NGC 5128: evidence of a low mass accretion.
MOUHCINE M., HARRIS W.E., IBATA R. and REJKUBA M.
Abstract (from CDS):
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∼ 17pc, placing it among the largest globular clusters known. The faint absolute magnitude of the star cluster, M_V,{cir}_= -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. ≳8Gyr, intermediate metallicity, i.e. [M/H] ∼ -1.0dex, stellar population. We also report the detection of a second, even fainter cluster candidate which would have rh∼ 9pc and M_V,{cir}_= -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.
Abstract Copyright:
© 2010 The Authors. Journal compilation © 2010 RAS
Journal keyword(s):
galaxies: formation - galaxies: individual: NGC 5128 - galaxies: photometry - galaxies: stellar content
Nomenclature:
Table 1: [WHB2007] GCNNNN (Nos 0606-0607) added.
Simbad objects:
21
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