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The SLUGGS Survey: stellar kinematics, kinemetry and trends at large radii in 25 early-type galaxies

Foster, C and Pastorello, N and Roediger, J and Brodie, JP and Forbes, DA and Kartha, SS and Pota, V and Romanowsky, AJ and Spitler, LR and Strader, J and Usher, CG and Arnold, JA (2016) The SLUGGS Survey: stellar kinematics, kinemetry and trends at large radii in 25 early-type galaxies. Monthly Notices of the Royal Astronomical Society, 457 (1). pp. 147-171. ISSN 0035-8711

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Abstract

Due to longer dynamical time-scales, the outskirts of early-type galaxies retain the footprint of their formation and assembly. Under the popular two-phase galaxy formation scenario, an initial in situ phase of star formation is followed by minor merging and accretion of ex situ stars leading to the expectation of observable transitions in the kinematics and stellar populations on large scales. However, observing the faint galactic outskirts is challenging, often leaving the transition unexplored. The large-scale, spatially resolved stellar kinematic data from the SAGES Legacy Unifying Galaxies and GlobularS (SLUGGS) survey are ideal for detecting kinematic transitions. We present kinematic maps out to 2.6 effective radii on average, kinemetry profiles, measurement of kinematic twists and misalignments, and the average outer intrinsic shape of 25 SLUGGS galaxies. We find good overall agreement in the kinematic maps and kinemetry radial profiles with literature. We are able to confirm significant radial modulations in rotational versus pressure support of galaxies with radius so that the central and outer rotational properties may be quite different. We also test the suggestion that galaxies may be more triaxial in their outskirts and find that while fast rotating galaxies were already shown to be axisymmetric in their inner regions, we are unable to rule out triaxiality in their outskirts.We compare our derived outer kinematic information to model predictions from a two-phase galaxy formation scenario. We find that the theoretical range of local outer angular momentum agrees well with our observations, but that radial modulations are much smaller than predicted.

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: 03 Mar 2016 15:06
Last Modified: 03 Mar 2016 15:06
DOI or Identification number: 10.1093/mnras/stv2947
URI: http://researchonline.ljmu.ac.uk/id/eprint/3067

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