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26 April 2024 |
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The peculiar motions of early-type galaxies in two distant regions - V. The Mg-sigma relation, age and metallicity | | Matthew Colless
; David Burstein
; Roger L. Davies
; Robert K. McMahan
; R. P. Saglia
; Gary Wegner
; | | Date: |
5 Nov 1998 | | Subject: | astro-ph | | Abstract: | We examine the Mg-sigma relation for early-type galaxies in the EFAR sample and its dependence on cluster properties. A maximum likelihood fit gives global Mg-sigma relations of Mgb’=0.131log(sigma)-0.131 and Mg2=0.257log(sigma)-0.305, with intrinsic scatter of 0.016 mag in Mgb’ and 0.023 mag in Mg2. The zeropoint for cD galaxies is higher than for E/S0 galaxies, implying cDs are older and/or more metal-rich than E/S0s with the same sigma. Mg-sigma zeropoint variations between clusters are consistent with the number of galaxies observed per cluster and the global intrinsic scatter in Mg-sigma. We find no significant correlation between the Mg-sigma zeropoint and the cluster velocity dispersion, X-ray luminosity or X-ray temperature over a wide range in cluster mass. We compare the intrinsic scatter in the Mg-sigma and Fundamental Plane (FP) relations with stellar population models to constrain the dispersion in ages, metallicities and M/L ratios for early-type galaxies at fixed sigma. Variations in age alone or metallicity alone cannot explain the measured intrinsic scatter in both Mg-sigma and the FP. We derive the joint constraints on the dispersion in age and metallicity implied by the scatter in the Mg-sigma and FP relations for a simple Gaussian model. We find upper limits on the dispersions at fixed sigma of 32% in dt/t and 38% in dZ/Z if variations in age and metallicity are uncorrelated; only strongly anti-correlated variations lead to significantly higher upper limits. The joint distribution of residuals from the Mg-sigma and FP relations is only marginally consistent with a model having no correlation between age and metallicity, and is better-matched by a model in which age and metallicity variations are moderately anti-correlated, with younger galaxies being more metal-rich. (Abridged) | | Source: | arXiv, astro-ph/9811089 | | Services: | Forum | Review | PDF | Favorites | |
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