Curvature in the scaling relations of early-type galaxies

Understand

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 BCGs 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 curva-ture.