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Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/95156
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- Early-type galaxies at large galactocentric radii I: stellar kinematics and photometric properties
- Spolaor, Max; Hau, George K. T.; Forbes, Duncan A.; Couch, Warrick J.
- 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
- Monthly Notices of the Royal Astronomical Society, Vol. 408, no. 1 (Oct 2010), pp. 254-271
- Publication year
- Wiley-Blackwell Publishing
- Publisher URL
- Copyright © 2010 The Authors. Journal compilation copyright © 2010 RAS. Accepted manuscript reproduced here in accordance with the copyright policy of the publisher.