2010/07/19 by Genevieve J. Graves, S. M. Faber, Ricardo P. Schiavon · 32 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Elliptical galaxy #Fundamental plane (elliptical galaxies) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Lenticular galaxy #Physics #Sigma #Star formation #Stellar mass #Stellar population #Stellar, planetary, and galactic studies #Surface brightness #Velocity dispersion #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/721/1/278
published in The Astrophysical Journal 721(1), 278-296 (IOP Publishing) · 21 pages, 9 figures. Accepted to ApJ
arxiv created 2010/07/19 · openalex publication_date 2010/08/27 · arxiv updated 2015/05/19 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
In the three-dimensional parameter space defined by velocity dispersion (σ), effective radius ( R e ), and effective surface brightness ( I e ), early-type galaxies are observed to populate a two-dimensional fundamental plane (FP) with finite thickness. In Paper III of this series, we showed that the thickness of the FP is predominantly due to variations in the stellar mass surface density (Σ ⋆ ) inside the effective radius R e . These variations represent differences in the dark matter fraction inside R e (or possibly differences in the initial mass function) from galaxy to galaxy. This means that galaxies do not wind up below the FP at lower surface brightness due to the passive fading of their stellar populations; they are structurally different. Here, we show that these variations in Σ ⋆ at fixed dynamical mass ( M dyn ) are linked to differences in the galaxy stellar populations, and therefore to differences in their star formation histories. We demonstrate that the ensemble of stellar population and Σ ⋆ variations through the FP thickness can be explained by a model in which early-type galaxies at fixed M dyn have their star formation truncated at different times. The thickness of the FP can therefore be interpreted as a sequence of truncation times. Galaxies below the FP have earlier truncation times for a given M dyn , resulting in lower Σ ⋆ , older ages, lower metallicities in both [Fe/H] and [Mg/H], and higher [Mg/Fe]. We show that this model is quantitatively consistent with simple expectations for chemical enrichment in galaxies. We also present fitting functions for luminosity-weighted age, [Fe/H], [Mg/H], and [Mg/Fe] as functions of the FP parameters σ, R e , and I e . These provide a new tool for estimating the stellar population properties of quiescent early-type galaxies for which high-quality spectra are not available.