Early-type Galaxies in the Sloan Digital Sky Survey. II. Correlations between Observables


Bernardi M, Sheth RK, Annis J, Burles S, Eisenstein DJ, Finkbeiner DP, Hogg DW, Lupton RH, Schlegel DJ, SubbaRao M, et al. Early-type Galaxies in the Sloan Digital Sky Survey. II. Correlations between Observables. The Astronomical Journal. 2003;125 :1849-1865.

Date Published:

April 1, 2003


A magnitude-limited sample of nearly 9000 early-type galaxies, in theredshift range 0.01<=z<=0.3, was selected from the Sloan DigitalSky Survey using morphological and spectral criteria. The sample wasused to study how early-type galaxy observables, including luminosity L,effective radius Ro, surface brightness Io, color,and velocity dispersion σ, are correlated with one another.Measurement biases are understood with mock catalogs that reproduce allof the observed scaling relations and their dependences on fittingtechnique. At any given redshift, the intrinsic distribution ofluminosities, sizes, and velocity dispersions in our sample are allapproximately Gaussian. A maximum likelihood analysis shows thatσ~L0.25+/-0.012,Ro~L0.63+/-0.025, andRo~I-0.75+/-0.02 in the r* band. In addition, themass-to-light ratio within the effective radius scales asMo/L~L0.14+/-0.02 orMo/L~M0.22+/-0.05o, and galaxies withlarger effective masses have smaller effective densities:Δo~M-0.52+/-0.03o. Theserelations are approximately the same in the g*, i*, and z* bands.Relative to the population at the median redshift in the sample,galaxies at lower and higher redshifts have evolved only little, withmore evolution in the bluer bands. The luminosity function is consistentwith weak passive luminosity evolution and a formation time of about 9Gyr ago.