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The stellar populations of the M31 halo substructure

Ferguson, A M N; Johnson, R A; Faria, Daniel LU ; Irwin, M J; Ibata, R A; Johnston, K V; Lewis, G F and Tanvir, N R (2005) In Astrophysical Journal 622(2). p.109-112
Abstract
We present the first results from our survey of stellar substructure in the outskirts of M31 using the Advanced Camera for Surveys on board the Hubble Space Telescope. We discuss the stellar populations associated with five prominent stellar overdensities discovered during the course of our panoramic ground-based imaging survey with the Isaac Newton Telescope Wide-Field Camera; a sixth pointing targets a region of "clean" halo. The color-magnitude diagrams, which contain between approximate to 10,000 and 90,000 stars and reach 4 mag below the horizontal branch, reveal clear variations in morphology between most fields, indicating that the age and/or metallicity mix of stars is not constant at large radius. This directly confirms the... (More)
We present the first results from our survey of stellar substructure in the outskirts of M31 using the Advanced Camera for Surveys on board the Hubble Space Telescope. We discuss the stellar populations associated with five prominent stellar overdensities discovered during the course of our panoramic ground-based imaging survey with the Isaac Newton Telescope Wide-Field Camera; a sixth pointing targets a region of "clean" halo. The color-magnitude diagrams, which contain between approximate to 10,000 and 90,000 stars and reach 4 mag below the horizontal branch, reveal clear variations in morphology between most fields, indicating that the age and/or metallicity mix of stars is not constant at large radius. This directly confirms the existence of large-scale population inhomogeneities within the halo of M31 and lends further support to the notion that M31 has formed, at least in part, through satellite accretions. We find a striking similarity between the populations of the giant stellar stream and those of another overdensity, the NE shelf, which lies northeast of the galaxy center. If these overdensities are associated with the same population, then the difference in their red clump magnitudes implies that the NE shelf lies in front of the stream by several tens of kiloparsecs, in good agreement with recent orbit calculations for the stream progenitor. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
galaxies : stellar content, : individual ( M31), galaxies, galaxies : halos, galaxies : evolution, galaxies : formation, galaxies : structure
in
Astrophysical Journal
volume
622
issue
2
pages
109 - 112
publisher
University of Chicago Press
external identifiers
  • wos:000228093800009
  • scopus:19944386582
ISSN
0004-637X
DOI
10.1086/429371
language
English
LU publication?
yes
id
0ac965b5-1337-4d72-a403-f2daa8320083 (old id 247218)
date added to LUP
2007-09-21 14:35:08
date last changed
2017-07-30 04:41:44
@article{0ac965b5-1337-4d72-a403-f2daa8320083,
  abstract     = {We present the first results from our survey of stellar substructure in the outskirts of M31 using the Advanced Camera for Surveys on board the Hubble Space Telescope. We discuss the stellar populations associated with five prominent stellar overdensities discovered during the course of our panoramic ground-based imaging survey with the Isaac Newton Telescope Wide-Field Camera; a sixth pointing targets a region of "clean" halo. The color-magnitude diagrams, which contain between approximate to 10,000 and 90,000 stars and reach 4 mag below the horizontal branch, reveal clear variations in morphology between most fields, indicating that the age and/or metallicity mix of stars is not constant at large radius. This directly confirms the existence of large-scale population inhomogeneities within the halo of M31 and lends further support to the notion that M31 has formed, at least in part, through satellite accretions. We find a striking similarity between the populations of the giant stellar stream and those of another overdensity, the NE shelf, which lies northeast of the galaxy center. If these overdensities are associated with the same population, then the difference in their red clump magnitudes implies that the NE shelf lies in front of the stream by several tens of kiloparsecs, in good agreement with recent orbit calculations for the stream progenitor.},
  author       = {Ferguson, A M N and Johnson, R A and Faria, Daniel and Irwin, M J and Ibata, R A and Johnston, K V and Lewis, G F and Tanvir, N R},
  issn         = {0004-637X},
  keyword      = {galaxies : stellar content,: individual ( M31),galaxies,galaxies : halos,galaxies : evolution,galaxies : formation,galaxies : structure},
  language     = {eng},
  number       = {2},
  pages        = {109--112},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {The stellar populations of the M31 halo substructure},
  url          = {http://dx.doi.org/10.1086/429371},
  volume       = {622},
  year         = {2005},
}