Journal Article

Are small-scale substructures a universal property of galaxy haloes? The case of the giant elliptical NGC 5128*

M. Mouhcine, R. Ibata and M. Rejkuba

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 2, pages 993-1001
Published in print August 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI:
Are small-scale substructures a universal property of galaxy haloes? The case of the giant elliptical NGC 5128*

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We present an analysis of the spatial and chemical substructures in a remote halo field in the nearby giant elliptical galaxy Centaurus A (NGC 5128), situated ∼38 kpc from the centre of the galaxy. The observations were taken with the Advanced Camera for Surveys instrument on-board the Hubble Space Telescope, and reach down to the horizontal branch. In this relatively small 3.8 × 3.8 kpc2 field, after correcting for Poisson noise, we do not find any statistically strong evidence for the presence of small-scale substructures in the stellar spatial distribution on scales ≳100 pc. However, we do detect the presence of significant small spatial-scale inhomogeneities in the stellar median metallicity over the surveyed field. We argue that these localized chemical substructures could be associated with not fully mixed debris from the disruption of low-mass systems. NGC 5128 joins the ranks of the late-type spiral galaxies the Milky Way, for which the stellar halo appears to be dominated by small-scale spatial substructures, and NGC 891, where localized metallicity variations have been detected in the inner extraplanar regions. This suggests that the presence of small-scale substructures may be a generic property of stellar haloes of large galaxies.

Keywords: galaxies: formation; galaxies: haloes; galaxies: individual: NGC 5128; galaxies: stellar content

Journal Article.  6490 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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