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Title

Early-type galaxies at large galactocentric radii I: stellar kinematics and photometric properties

Author(s)

Spolaor, Max;  Hau, George K. T.;  Forbes, Duncan A.;  Couch, Warrick J.

Abstract

We present the results of a combined analysis of the kinematic and photometric properties at large galactocentric radii of a sample of 14 low-luminosity early-type galaxies in the Fornax and Virgo clusters. From Gemini South GMOS long-slit spectroscopic data, we measure radial profiles of the kinematic parameters vrot, σ, h3 and h4 out to ∼1–3 effective radii. Multiband imaging data from the Hubble Space Telescope/ACS are employed to evaluate surface brightness profiles and isophotal shape parameters of ellipticity, position angle and discyness/boxiness. The galaxies are found to host a cold and old stellar component which extend to the largest observed radii and that is the dominant source of their dynamical support. The prevalence of discy-shaped isophotes and the radial variation of their ellipticity are signatures of a gradual gas dissipation. An early star-forming collapse appears to be the main mechanism acting in the formation of these objects. Major mergers are unlikely to have occurred in these galaxies. We cannot rule out a minor merging origin for these galaxies, but a comparison of our results with model predictions of different merger categories places some constraints on the possible merger progenitors. These merger events are required to happen at high-redshift (i.e. z≥ 1), between progenitors of different mass ratio (at least 3:1) and containing a significant amount of gas (i.e. ≥10 per cent). A further scenario is that the low-luminosity galaxies were originally late-type galaxies, whose star formation has been truncated by removal of gas and subsequently the disc has been dynamically heated by high-speed encounters in the cluster environment.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Monthly Notices of the Royal Astronomical Society, Vol. 408, no. 1 (Oct 2010), pp. 254-271

Publication year

2010

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Dwarf galaxies;  Dynamical support;  Elliptical galaxies;  Galaxy evolution;  Galaxy formation;  Kinematics;  Lenticular galaxies;  Photometry

Publisher

Wiley-Blackwell Publishing

ISSN

0035-8711

Publisher URL

http://dx.doi.org/10.1111/j.1365-2966.2010.17282.x

Copyright

Copyright © 2010 The Authors. Journal compilation copyright © 2010 RAS. Accepted manuscript reproduced here in accordance with the copyright policy of the publisher.

Full text

Peer reviewed