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The SLUGGS survey: globular clusters and the dark matter content of early-type galaxies

Forbes, DA and Alabi, A and Romanowsky, AJ and Brodie, JP and Strader, J and Usher, CG and Pota, V (2016) The SLUGGS survey: globular clusters and the dark matter content of early-type galaxies. Monthly Notices of the Royal Astronomical Society: Letters, 458 (1). L44-L48. ISSN 1745-3933

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Abstract

A strong correlation exists between the total mass of a globular cluster (GC) system and the virial halo mass of the host galaxy. However, the total halo mass in this correlation is a statistical measure conducted on spatial scales that are some 10 times that of a typical GC system. Here we investigate the connection between GC systems and galaxy's dark matter on comparable spatial scales, using dynamical masses measured on a galaxy-by-galaxy basis. Our sample consists of 17 well-studied massive (~10 x 11 M☉) early-type galaxies from the SLUGGS survey. We find the strongest correlation to be that of the blue (metal-poor) GC subpopulation and the dark matter content. This correlation implies that the dark matter mass of a galaxy can be estimated to within a factor of 2 from careful imaging of its GC system. The ratio of the GC system mass to that of the enclosed dark matter is nearly constant. We also find a strong correlation between the fraction of blue GCs and the fraction of enclosed dark matter, so that a typical galaxy with a blue GC fraction of 60 per cent has a dark matter fraction of 86 per cent over similar spatial scales. Both halo growth and removal (via tidal stripping) may play some role in shaping this trend. In the context of the two-phase model for galaxy formation, we find galaxies with the highest fractions of accreted stars to have higher dark matter fractions for a given fraction of blue GCs.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Date Deposited: 10 Nov 2016 09:21
Last Modified: 07 Sep 2017 15:12
DOI or Identification number: 10.1093/mnrasl/slw015
URI: http://researchonline.ljmu.ac.uk/id/eprint/4773

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