• DOI:10.1086/323301
• Corpus ID: 21190490

Color Separation of Galaxy Types in the Sloan Digital Sky Survey Imaging Data

@article{Strateva2001ColorSO,
  title={Color Separation of Galaxy Types in the Sloan Digital Sky Survey Imaging Data},
  author={Iskra V. Strateva and Željko Ivezi{\'c} and Gillian R. Knapp and Vijay K. Narayanan and Michael A. Strauss and James E. Gunn and Robert H. Lupton and David J. Schlegel and Neta A. Bahcall and Jonathan Brinkmann and Robert J. Brunner and Tam{\'a}s Budav{\'a}ri and Istv{\'a}n Csabai and Francisco Javier Castander and Mamoru Doi and Masataka Fukugita and Zsuzsanna Győry and Masaru Hamabe and Gregory S. Hennessy and Takashi Ichikawa and Peter Z. Kunszt and Donald Q. Lamb and Timothy A. Mckay and Sadanori Okamura and Judith L. Racusin and Maki Sekiguchi and Donald P. Schneider and Kazuhiro Shimasaku and Donald G. York},
  journal={The Astronomical Journal},
  year={2001},
  volume={122},
  pages={1861 - 1874}
}

• I. Strateva, Ž. Ivezić, +26 authors D. York
• Published 11 July 2001
• Physics
• The Astronomical Journal

We study the optical colors of 147,920 galaxies brighter than g* = 21, observed in five bands by the Sloan Digital Sky Survey (SDSS) over ∼100 deg2 of high Galactic latitude sky along the celestial equator. The distribution of galaxies in the g*-r* versus u*-g* color-color diagram is strongly bimodal, with an optimal color separator of u*-r* = 2.22. We use visual morphology and spectral classification of subsamples of 287 and 500 galaxies, respectively, to show that the two peaks correspond roughly to early- (E, S0, and Sa) and late-type (Sb, Sc, and Irr) galaxies, as expected from their different stellar populations. We also find that the colors of galaxies are correlated with their radial profiles, as measured by the concentration index and by the likelihoods of exponential and de Vaucouleurs' profile fits. While it is well known that late-type galaxies are bluer than early-type galaxies, this is the first detection of a local minimum in their color distribution. In all SDSS bands, the counts versus apparent magnitude relations for the two color types are significantly different and demonstrate that the fraction of blue galaxies increases toward the faint end.