The 6dF Galaxy Survey: The Near-Infrared Fundamental Plane of Early-Type Galaxies

Jun, 2012
29 pages
Published in:
  • Mon.Not.Roy.Astron.Soc. 427 (2012) 245
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2012201520182021202402468
Abstract: (arXiv)
We determine the near-infrared Fundamental Plane (FP) for 104\sim10^4 early-type galaxies in the 6dF Galaxy Survey (6dFGS). We fit the distribution of central velocity dispersion, near-infrared surface brightness and half-light radius with a three-dimensional Gaussian model using a maximum likelihood method. For the 6dFGS JJ band sample we find a FP with ReR_{e}\,\propto\,σ01.52±0.03Ie0.89±0.01\sigma_0^{1.52\pm0.03}I_{e}^{-0.89\pm0.01}, similar to previous near-IR determinations and consistent with the HH and KK band Fundamental Planes once allowance is made for differences in mean colour. The overall scatter in ReR_e about the FP is σr\sigma_r,=,29%, and is the quadrature sum of an 18% scatter due to observational errors and a 23% intrinsic scatter. Because of the distribution of galaxies in FP space, σr\sigma_r is not the distance error, which we find to be σd\sigma_d,=,23%. Using group richness and local density as measures of environment, and morphologies based on visual classifications, we find that the FP slopes do not vary with environment or morphology. However, for fixed velocity dispersion and surface brightness, field galaxies are on average 5% larger than galaxies in higher-density environments, and the bulges of early-type spirals are on average 10% larger than ellipticals and lenticulars. The residuals about the FP show significant trends with environment, morphology and stellar population. The strongest trend is with age, and we speculate that age is the most important systematic source of offsets from the FP, and may drive the other trends through its correlations with environment, morphology and metallicity.
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