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Article
The AIMSS Project – III. The stellar populations of compact stellar systems
Monthly Notices of the Royal Astronomical Society (2016)
  • Joachim Janz, Swinburne University of Technology
  • Mark A. Norris, Max Planck Institute for Astronomy
  • Duncan A. Forbes, Swinburne University of Technology
  • Avon Huxor, Universität Heidelberg
  • Aaron J. Romanowsky, San Jose State University
  • Matthias J. Frank, Universität Heidelberg
  • Carlos G. Escudero, Universidad Nacional de La Plata
  • Favio R. Faifer, Universidad Nacional de La Plata
  • Juan Carlos Forte, Consejo Nacional de Investigaciones Científicas y Técnicas
  • Sheila J. Kannappan, University of North Carolina at Chapel Hill
  • Claudia Maraston, Institute of Cosmology and Gravitation
  • Jean P. Brodie, University of California Observatories
  • Jay Strader, Michigan State University
  • Bradley R. Thompson, San Jose State University
Abstract
In recent years, a growing zoo of compact stellar systems (CSSs) have been found whose physical properties (mass, size, velocity dispersion) place them between classical globular clusters (GCs) and true galaxies, leading to debates about their nature. Here we present results using a so far underutilized discriminant, their stellar population properties. Based on new spectroscopy from 8–10m telescopes, we derive ages, metallicities, and [α/Fe] of 29 CSSs. These range from GCs with sizes of merely a few parsec to compact ellipticals (cEs) larger than M32. Together with a literature compilation, this provides a panoramic view of the stellar population characteristics of early-type systems. We find that the CSSs are predominantly more metal rich than typical galaxies at the same stellar mass. At high mass, the cEs depart from the mass–metallicity relation of massive early-type galaxies, which forms a continuous sequence with dwarf galaxies. At lower mass, the metallicity distribution of ultracompact dwarfs (UCDs) changes at a few times 107 M⊙, which roughly coincides with the mass where luminosity function arguments previously suggested the GC population ends. The highest metallicities in CSSs are paralleled only by those of dwarf galaxy nuclei and the central parts of massive early types. These findings can be interpreted as CSSs previously being more massive and undergoing tidal interactions to obtain their current mass and compact size. Such an interpretation is supported by CSSs with direct evidence for tidal stripping, and by an examination of the CSS internal escape velocities.
Keywords
  • galaxies: fundamental parameters,
  • galaxies: stellar content
Publication Date
February, 2016
DOI
10.1093/mnras/stv2636
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.
This article is also available online at the following link: http://dx.doi.org/10.1093/mnras/stv2636
Citation Information
Joachim Janz, Mark A. Norris, Duncan A. Forbes, Avon Huxor, et al.. "The AIMSS Project – III. The stellar populations of compact stellar systems" Monthly Notices of the Royal Astronomical Society Vol. 456 Iss. 1 (2016) p. 617 - 632 ISSN: 1365-2966
Available at: http://works.bepress.com/aaron_romanowsky/87/