Document Type
Article
Publication Date
February 2016
Publication Title
Monthly Notices of the Royal Astronomical Society
Volume
456
Issue Number
1
First Page
617
Last Page
632
DOI
10.1093/mnras/stv2636
Keywords
galaxies: fundamental parameters, galaxies: stellar content
Disciplines
Astrophysics and Astronomy | External Galaxies
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.
Recommended Citation
Joachim Janz, Mark Norris, Duncan Forbes, Avon Huxor, Aaron Romanowsky, Matthias Frank, Carlos Escudero, Favio Faifer, Juan Forte, Sheila Kannappan, Claudia Maraston, Jean Brodie, Jay Strader, and Bradley Thompson. "The AIMSS Project – III. The stellar populations of compact stellar systems" Monthly Notices of the Royal Astronomical Society (2016): 617-632. https://doi.org/10.1093/mnras/stv2636
Comments
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