Journal Article

Curvature in the scaling relations of early-type galaxies

Joseph B. Hyde and Mariangela Bernardi

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 394, issue 4, pages 1978-1990
Published in print April 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI:
Curvature in the scaling relations of early-type galaxies

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We select a sample of about 50 000 early-type galaxies from the Sloan Digital Sky Survey (SDSS), calibrate fitting formulae which correct for known problems with photometric reductions of extended objects, apply these corrections and then measure a number of pairwise scaling relations in the corrected sample. We show that, because they are not seeing corrected, the use of Petrosian-based quantities in magnitude-limited surveys leads to biases, and suggest that this is one reason why Petrosian-based analyses of brightest cluster galaxies have failed to find significant differences from the bulk of the early-type population. These biases are not present when seeing-corrected parameters derived from deVaucouleur fits are used. Most of the scaling relations we study show evidence for curvature: the most luminous galaxies have smaller velocity dispersions, larger sizes and fainter surface brightnesses than expected if there were no curvature. These statements remain true if we replace luminosities with stellar masses; they suggest that dissipation is less important at the massive end. There is curvature in the dynamical to stellar mass relation as well: the ratio of dynamical to stellar mass increases as stellar mass increases, but it curves upwards from this scaling both at small and at large stellar masses. In all cases, the curvature at low masses becomes apparent when the sample becomes dominated by objects with stellar masses smaller than 3 × 1010 M. We quantify all these trends using second-order polynomials; these generally provide significantly better description of the data than linear fits, except at the least luminous end.

Keywords: methods: analytical; galaxies: formation; galaxies: haloes; dark matter; large-scale structure of Universe

Journal Article.  8241 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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