Velocity dispersion measurements of dwarf galaxies in the Coma cluster – implications for the structure of the fundamental plane

• Published in: Monthly notices of the Royal Astronomical Society Vol. 396; no. 3; pp. 1647 - 1658
• Main Authors: Cody, A. M., Carter, D., Bridges, T. J., Mobasher, B., Poggianti, B. M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-07-2009; Wiley-Blackwell; Oxford University Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; galaxies: clusters: individual: Coma; galaxies: dwarf; galaxies: elliptical and lenticular; galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: fundamental parameters; galaxies: kinematics and dynamics; Kinematics; Luminosity; Spectrum analysis; Stars & galaxies; Velocity; galaxies: dwarf; galaxies: elliptical and lenticular, cD; galaxies: fundamental parameters; galaxies: kinematics and dynamics; galaxies: evolution; galaxies: clusters: individual: Coma; Galaxy evolution; Galactic wind; Elliptical galaxies; Luminosity; Velocity dispersion; Galaxy clusters; Giant galaxies; Theoretical model; Dynamics; Dwarf galaxies; Correlations; Kinematics
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2009.14826.x

We present intermediate–resolution spectroscopic data for a set of dwarf and giant galaxies in the Coma cluster, with −20.6 < MR < −15.7. The photometric and kinematic properties of the brighter galaxies can be cast in terms of parameters which present little scatter with respect to a set of scaling relations known as the fundamental plane. To determine the form of these fundamental scaling relations at lower luminosities, we have measured velocity dispersions for a sample comprising 69 galaxies on the border of the dwarf and giant regime. Combining these data with our photometric survey, we find a tight correlation of luminosity and velocity dispersion, L∝σ2.0, substantially flatter than the Faber–Jackson relation characterizing giant elliptical galaxies. In addition, the variation of mass–to–light (M/L) ratio with velocity dispersion is quite weak in our dwarf sample: M/L∝σ0.2. Our overall results are consistent with theoretical models invoking large–scale mass removal and subsequent structural readjustment, e.g. as a result of galactic winds.