2010/07/05 by Max Spolaor, George K. T. Hau, Duncan A. Forbes +1 · 21 citations
Physics and Astronomy · #Astronomy #Astrophysics #Elliptical galaxy #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Gamma-ray bursts and supernovae #Luminosity #Luminous infrared galaxy #Physics #Star formation #Stellar, planetary, and galactic studies #Surface brightness #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1111/j.1365-2966.2010.17282.x
published in Monthly Notices of the Royal Astronomical Society 408(1), 254-271 (Oxford University Press) · 19 pages, 16 figures (Contact author for high resolution version of figures 1,2,3), MNRAS, accepted. The second paper of the series "Early-type galaxies at large galactocentric radii - II. Metallicity gradients and the [Z/H]-mass, [alpha/Fe] mass relations" can be found at arXiv:1006.1698
arxiv created 2010/07/05 · arxiv updated 2015/05/19
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.