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The structure of star clusters in the outer halo of M31

Tanvir, N. R.; Mackey, A. D.; Ferguson, A. M. N.; Huxor, A.; Read, J. I.; Lewis, G. F.; Irwin, M. J.; Chapman, S.; Ibata, R. and Wilkinson, M. I., et al. (2012) In Monthly Notices of the Royal Astronomical Society 422(1). p.162-184
Abstract
We present a structural analysis of halo star clusters in M31 based on deep Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging. The clusters in our sample span a range in galactocentric projected distance from 13 to 100 kpc and thus reside in rather remote environments. Ten of the clusters are classical globulars, whilst four are from the Huxor et al. population of extended, old clusters. For most clusters, contamination by M31 halo stars is slight, and so the profiles can be mapped reliably to large radial distances from their centres. We find that the extended clusters are well fit by analytic King profiles with similar to 20 parsec core radii and similar to 100 parsec photometric tidal radii, or by Sersic profiles of... (More)
We present a structural analysis of halo star clusters in M31 based on deep Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging. The clusters in our sample span a range in galactocentric projected distance from 13 to 100 kpc and thus reside in rather remote environments. Ten of the clusters are classical globulars, whilst four are from the Huxor et al. population of extended, old clusters. For most clusters, contamination by M31 halo stars is slight, and so the profiles can be mapped reliably to large radial distances from their centres. We find that the extended clusters are well fit by analytic King profiles with similar to 20 parsec core radii and similar to 100 parsec photometric tidal radii, or by Sersic profiles of index similar to 1 (i.e. approximately exponential). Most of the classical globulars also have large photometric tidal radii in the range 50-100 parsec; however, the King profile is a less good fit in some cases, particularly at small radii. We find 60 per cent of the classical globular clusters exhibit cuspy cores which are reasonably well described by Sersic profiles of index similar to 2-6. Our analysis also reinforces the finding that luminous classical globulars, with half-light radii <10 parsec, are present out to radii of at least 100 kpc in M31, which is in contrast to the situation in the Milky Way where such clusters (other than the unusual object NGC 2419) are absent beyond 40 kpc. (Less)
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subject
keywords
galaxies: haloes, galaxies: star clusters: general, galaxies:, individual: M31
in
Monthly Notices of the Royal Astronomical Society
volume
422
issue
1
pages
162 - 184
publisher
Wiley-Blackwell
external identifiers
  • wos:000303912600032
  • scopus:84859881278
ISSN
1365-2966
DOI
10.1111/j.1365-2966.2012.20590.x
language
English
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yes
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ece9eb7c-6f19-4c9b-8b59-b587ab0d6454 (old id 2813030)
date added to LUP
2012-06-25 09:16:10
date last changed
2017-07-30 03:02:03
@article{ece9eb7c-6f19-4c9b-8b59-b587ab0d6454,
  abstract     = {We present a structural analysis of halo star clusters in M31 based on deep Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging. The clusters in our sample span a range in galactocentric projected distance from 13 to 100 kpc and thus reside in rather remote environments. Ten of the clusters are classical globulars, whilst four are from the Huxor et al. population of extended, old clusters. For most clusters, contamination by M31 halo stars is slight, and so the profiles can be mapped reliably to large radial distances from their centres. We find that the extended clusters are well fit by analytic King profiles with similar to 20 parsec core radii and similar to 100 parsec photometric tidal radii, or by Sersic profiles of index similar to 1 (i.e. approximately exponential). Most of the classical globulars also have large photometric tidal radii in the range 50-100 parsec; however, the King profile is a less good fit in some cases, particularly at small radii. We find 60 per cent of the classical globular clusters exhibit cuspy cores which are reasonably well described by Sersic profiles of index similar to 2-6. Our analysis also reinforces the finding that luminous classical globulars, with half-light radii &lt;10 parsec, are present out to radii of at least 100 kpc in M31, which is in contrast to the situation in the Milky Way where such clusters (other than the unusual object NGC 2419) are absent beyond 40 kpc.},
  author       = {Tanvir, N. R. and Mackey, A. D. and Ferguson, A. M. N. and Huxor, A. and Read, J. I. and Lewis, G. F. and Irwin, M. J. and Chapman, S. and Ibata, R. and Wilkinson, M. I. and McConnachie, A. W. and Martin, N. F. and Davies, Melvyn B and Bridges, T. J.},
  issn         = {1365-2966},
  keyword      = {galaxies: haloes,galaxies: star clusters: general,galaxies:,individual: M31},
  language     = {eng},
  number       = {1},
  pages        = {162--184},
  publisher    = {Wiley-Blackwell},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {The structure of star clusters in the outer halo of M31},
  url          = {http://dx.doi.org/10.1111/j.1365-2966.2012.20590.x},
  volume       = {422},
  year         = {2012},
}