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The SLUGGS survey: combining stellar and globular cluster metallicities in the outer regions of early-type galaxies
Monthly Notices of the Royal Astronomical Society (2015)
  • Nicola Pastorello, Swinburne University of Technology
  • Duncan A. Forbes, Swinburne University of Technology
  • Christopher Usher, Swinburne University of Technology
  • Jean P. Brodie, University of California Observatories
  • Aaron J. Romanowsky, San Jose State University
  • Jay Strader, Michigan State University
  • Lee R. Spitler, Macquarie University
  • Adebusola B. Alabi, Swinburne University of Technology
  • Caroline Foster, Australian Astronomical Observatory
  • Zachary G. Jennings, University of California Observatories
  • Sreeja S. Kartha, Swinburne University of Technology
  • Vincenzo Pota, University of California Observatories
The outer halo regions of early-type galaxies carry key information about their past accretion history. However, spectroscopically probing the stellar component at such galactocentric radii is still challenging. Using the DEep Imaging Multi-Object Spectrograph on the Keck, we have been able to measure the metallicities of the stellar and globular cluster components in 12 early-type galaxies out to more than 10Re. We find similar metallicity gradients for the metal-poor and metal-rich globular cluster subpopulations, suggesting a common formation process for the two subpopulations. This is in conflict with most current theoretical predictions, where the metal-poor globular clusters are thought to be purely accreted and metal-rich globular clusters mostly formed in situ. Moreover, we find that the globular cluster metallicity gradients show a trend with galaxy mass, being steeper in lower mass galaxies than in higher mass galaxies. This is similar to what we find for the outermost galaxy stars and suggests a more active accretion history, with a larger role played by major mergers, in the most massive galaxies. This conclusion is qualitatively consistent with expectations from two-phase galaxy assembly models. Finally, we find that the small difference in metallicity between galaxy stars and metal-rich globular clusters at 1Re may correlate with galaxy mass. The origin of this difference is not currently clear.
  • galaxies: abundances,
  • galaxies: elliptical and lenticular,
  • cD,
  • galaxies: evolution,
  • galaxies: formation,
  • galaxies: star clusters: general,
  • galaxies: stellar content
Publication Date
August, 2015
Publisher Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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Citation Information
Nicola Pastorello, Duncan A. Forbes, Christopher Usher, Jean P. Brodie, et al.. "The SLUGGS survey: combining stellar and globular cluster metallicities in the outer regions of early-type galaxies" Monthly Notices of the Royal Astronomical Society Vol. 451 Iss. 3 (2015) p. 2625 - 2639 ISSN: 1365-2966
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