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The SLUGGS survey: the assembly histories of individual early-type galaxies

Forbes, DA and Romanowsky, AJ and Pastorello, N and Foster, C and Brodie, JP and Strader, J and Usher, CG and Pota, V (2016) The SLUGGS survey: the assembly histories of individual early-type galaxies. Monthly Notices of the Royal Astronomical Society, 457 (2). pp. 1242-1256. ISSN 0035-8711

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Abstract

Early-type (E and S0) galaxies may have assembled via a variety of different evolutionary pathways. Here, we investigate these pathways by comparing the stellar kinematic properties of 24 early-type galaxies from the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey with the hydrodynamical simulations of Naab et al. In particular, we use the kinematics of starlight up to 4 effective radii (Re) as diagnostics of galaxy inner and outer regions, and assign each galaxy to one of six Naab et al. assembly classes. The majority of our galaxies (14/24) have kinematic characteristics that indicate an assembly history dominated by gradual gas dissipation and accretion of many gas-rich minor mergers. Three galaxies, all S0s, indicate that they have experienced gas-rich major mergers in their more recent past. One additional elliptical galaxy is tentatively associated with a gas-rich merger which results in a remnant galaxy with low angular momentum. Pathways dominated by gas-poor (major or minor) mergers dominate the mass growth of six galaxies. Most SLUGGS galaxies appear to have grown in mass (and size) via the accretion of stars and gas from minor mergers, with late major mergers playing a much smaller role. We find that the fraction of accreted stars correlates with the stellar mean age and metallicity gradient, but not with the slope of the total mass density profile. We briefly mention future observational and modelling approaches that will enhance our ability to accurately reconstruct the assembly histories of individual present-day galaxies.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 Christopher Usher et al. 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
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Date Deposited: 04 Mar 2016 11:47
Last Modified: 04 Mar 2016 11:47
DOI or Identification number: 10.1093/mnras/stv3021
URI: http://researchonline.ljmu.ac.uk/id/eprint/3072

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