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The SLUGGS Survey: Measuring globular cluster ages using both photometry and spectroscopy

Usher, CG, Brodie, JP, Forbes, DA, Romanowsky, AJ, Strader, J, Pfeffer, J and Bastian, N (2019) The SLUGGS Survey: Measuring globular cluster ages using both photometry and spectroscopy. Monthly Notices of the Royal Astronomical Society, 490 (1). pp. 491-501. ISSN 0035-8711

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Abstract

Globular cluster ages provide both an important test of models of globular cluster formation and a powerful method to constrain the assembly history of galaxies. Unfortunately, measuring the ages of unresolved old stellar populations has proven challenging. Here, we present a novel technique that combines optical photometry with metallicity constraints from near-infrared spectroscopy in order to measure ages. After testing the method on globular clusters in the Milky Way and its satellite galaxies, we apply our technique to three massive early-type galaxies using data from the SLUGGS Survey. The three SLUGGS galaxies and the Milky Way show dramatically different globular cluster age and metallicity distributions, with NGC 1407 and the Milky Way showing mostly old globular clusters while NGC 3115 and NGC 3377 show a range of globular ages. This diversity implies different galaxy formation histories and that the globular cluster optical colour-metallicity relation is not universal as is commonly assumed in globular cluster studies. We find a correlation between the median age of the metal rich globular cluster populations and the age of the field star populations, in line with models where globular cluster formation is a natural outcome of high intensity star formation.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 11 Nov 2019 10:13
Last Modified: 11 Nov 2019 10:15
DOI or Identification number: 10.1093/mnras/stz2596
URI: http://researchonline.ljmu.ac.uk/id/eprint/11740

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