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Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/42763
- The bimodal galaxy color distribution: dependence on luminosity and environment
- Balogh, Michael L.; Baldry, Ivan K.; Nichol, Robert C.; Miller, Christopher J.; Bower, Richard G.; Glazebrook, Karl
- We analyze the u - r color distribution of 24,346 galaxies with M r ≤ -18 and z < 0.08, drawn from the Sloan Digital Sky Survey first data release, as a function of luminosity and environment. The color distribution is well fitted with two Gaussian distributions, which we use to divide the sample into a blue and red population. At fixed luminosity, the mean color of the blue (red) distribution is nearly independent of environment, with a weakly significant (∼3 σ) detection of a trend for colors to become redder by 0.1-0.14 (0.03-0.06) mag with a factor of ∼100 increase in local density, as characterized by the surface density of galaxies within a ±1000 km s 1 redshift slice. In contrast, at fixed luminosity the fraction of galaxies in the red distribution is a strong function of local density, increasing from ∼10%-30% of the population in the lowest density environments to ∼70% at the highest densities. The strength of this trend is similar for both the brightest (-23 < Mr < -22) and faintest (-19 < Mr < -18) galaxies in our sample. The fraction of red galaxies within the virialized regions of clusters shows no significant dependence on velocity dispersion. Even at the lowest densities explored, a substantial population of red galaxies exists, which might be fossil groups. We propose that most star-forming galaxies today evolve at a rate that is determined primarily by their intrinsic properties and independent of their environment. Any environmentally triggered transformations from blue to red colors must occur either on a short timescale or preferentially at high redshift to preserve the simple Gaussian nature of the color distribution. The mechanism must be effective for both bright and faint galaxies.
- Publication type
- Journal article
- Astrophysical Journal, Vol. 615, no. 2 (Nov 2004), pp. L101-L104
- Publication year
- Clusters; Digital sky survey; Evolution; Galaxies; Magnitude relation; Morphology-density relation; Redshift; S0 galaxies; Star-formation; Tully-fisher relation
- University of Chicago
- Publisher URL
- Copyright © 2004 The American Astronomical Society. All rights reserved.
- Peer reviewed