Browsing by Author "Carter, D"

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    Kinematics, abundances and origin of brightest cluster galaxies
    (1999) Carter, D; Bridges, TJ; Hau, GKT
    We present kinematic parameters and absorption line strengths for three brightest cluster galaxies, NGC 6166, 6173 and 6086. We find that NGC 6166 has a velocity dispersion profile which rises beyond 20 arcsec from the nucleus, with a halo velocity dispersion in excess of 400 km s(-1). All three galaxies show a positive and constant h(4) Hermite moment. The rising velocity dispersion profile in NGC 6166 thus indicates an increasing mass-to-light ratio. Rotation is low in all three galaxies, and NGC 6173 and 6086 show possible kinematically decoupled cores. All three galaxies have Mg-2 gradients similar to those found in normal bright ellipticals, which are not steep enough to support simple dissipative collapse models, but these could be accompanied by dissipationless mergers which would tend to dilute the abundance gradients. The [Mg/Fe] ratios in NGC 6166 and 6086 are higher than that found in NGC 6173, and if NGC 6173 is typical of normal bright ellipticals, this suggests that cDs cannot form from late mergers of normal galaxies.
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    The shell elliptical galaxy NGC 2865: evolutionary population synthesis of a kinematically distinct core
    (1999) Hau, GKT; Carter, D; Balcells, M
    We report on the discovery of a rapidly corotating stellar and gas component in the nucleus of the shell elliptical NGC 2865. The stellar component extends similar to 0.51 h(100)(-1) kpc along the major axis, and shows depressed velocity dispersion and absorption-line profiles skewed in the opposite sense to the mean velocity. Associated with it is a young stellar population with enhanced H beta, lowered Mg, and the same Fe indices relative to the underlying elliptical. Its recent star formation history is constrained by considering 'bulge+burst' models under four physically motivated scenarios, using evolutionary population synthesis. Scenarios in which the nuclear component is formed over a Hubble time or recently from continuous gas inflow are ruled out.