Early-type galaxies in the sloan digital sky survey. IV. Colors and chemical evolution

Mariangela Bernardi, Ravi K. Sheth, James Annis, Scott Burles, Douglas P. Finkbeiner, Robert H. Lupton, David J. Schlegel, Mark SubbaRao, Neta A. Bahcall, John P. Blakeslee, J. Brinkmann, Francisco J. Castander, Andrew J. Connolly, István Csabai, Mamoru Doi, Masataka Fukugita, Joshua Frieman, Tlmothy Heckman, Gregory S. Hennessy, Željko IvezićG. R. Knapp, Don Q. Lamb, Timothy McKay, Jeffrey A. Munn, Robert Nichol, Sadanori Okamura, Donald P. Schneider, Aniruddha R. Thakar, Donald G. York

Research output: Contribution to journalArticlepeer-review

176 Scopus citations


The colors and chemical abundances of early-type galaxies at redshifts z < 0.3 are studied using a sample of nearly 9000 galaxies, selected from the Sloan Digital Sky Survey using morphological and spectral criteria. In this sample, redder galaxies have larger velocity dispersions: g*-r* ∝ σ0.26±0.02. Color also correlates with magnitude, g* - r* ∝ (-0.025 ± 0.003)Mr*, and size, but these correlations are entirely due to the L-σ and R o-σ relations: the primary correlation is color-σ. The red light in early-type galaxies is, on average, slightly more centrally concentrated than the blue. Because of these color gradients, the strength of the color-magnitude relation depends on whether or not the colors are defined using a fixed metric aperture; the color-σ relation is less sensitive to this choice. Chemical evolution and star formation histories of early-type galaxies are investigated using co-added spectra of similar objects. The resulting library of co-added spectra contains spectra that represent a wide range of early-type galaxies. Chemical abundances correlate primarily with velocity dispersion: Hβ ∝ σ-0-24±0-03, Mg 2 ∝ σ0.20±0.02, Mg b ∝ σ 0.32±0.03 and 〈Fe〉 ∝ σ 0.11±0.03. At fixed with the population at z ∼ 0.2 had weaker Mg2 and stronger Hβ absorption compared to the population at z ∼ 0. It was also bluer. Comparison of these colors and line strengths and their evolution with single-burst stellar population models suggests a formation time of 9 Gyr ago, consistent with a fundamental plane analysis of this sample. Although the fundamental plane shows that galaxies in dense regions are slightly different from galaxies in less dense regions, the co-added spectra and color-magnitude relations show no statistically significant dependence on environment.

Original languageEnglish (US)
Pages (from-to)1882-1896
Number of pages15
JournalAstronomical Journal
Issue number4 1768
StatePublished - Apr 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: elliptical and lenticular, cD
  • Galaxies: evolution
  • Galaxies: fundamental parameters
  • Galaxies: photometry
  • Galaxies: stellar content


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