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

By I. Strateva, Željko Ivezic´, G. Knapp, V. Narayanan, M. Strauss, James E. Gunn, Robert Lupton, David Schlegel, N. Bahcall, J. Brinkmann and 19 more. 2001

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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.

Subfields: Astronomy and Astrophysics, Ecology

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Citations in the corpus

THE MASS–METALLICITY AND LUMINOSITY–METALLICITY RELATIONS FROM DEEP2 AT z ∼ 0.8 (2010, background): “The bimodal color distribution separates red early-type galaxies from blue late-type star forming galaxies (Strateva et al. 2001; Hogg et al. 2003; Baldry et al. 2004; Willmer et al. 2006).”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, methodology): “The tines of the tuningfork diagram correspond roughly to the red sequence and blue cloud in the SDSS color-magnitude diagram (Strateva et al. 2001; Bernardi et al. 2003; Hogg et al. 2002, 2004; Blanton et al. 2003, 2005; Baldry et al. 2004).”
The host galaxies of active galactic nuclei (2003, neutral): “As discussed in Strateva et al. (2001) and in C© 2003 RAS, MNRAS 346, 1055–1077 Downloaded from https://academic.oup.com/mnras/article-abstract/346/4/1055/1062435 by guest on 30 July 2018 Paper II, early-type galaxies (Hubble type Sa, S0 and E) have µ∗ in the range 3 × 108–3 × 109 M kpc−2 and C >…”
A universal ultraviolet–optical colour–colour–magnitude relation of galaxies★ (2011, methodology): “In the optical CMD (g − r, Mr) (Strateva et al. 2001; Blanton et al. 2003a; Baldry et al. 2004), the very narrow ‘red sequence’ (Visvanathan & Sandage 1977) [σ (g − r) ≈ 0.04 mag] formed mostly by elliptical and lenticular galaxies is used to identify earlytype members of galaxy clusters because at…”
The Luminosity and Color Dependence of the Galaxy Correlation Function (2004, background): “The g r galaxy color distribution is bimodal, similar to u r (Strateva et al. 2001), so we divide the sample at a rest-frame g r ¼ 0:7, which naturally separates the two populations.”
Semi-empirical analysis of Sloan Digital Sky Survey galaxies – II. The bimodality of the galaxy population revisited (2005, methodology): “Strateva et al. (2001) also studied the reliability of the concentration index to separate early- and late-type galaxies.”
CALIFA : a diameter-selected sample for an integral field spectroscopy galaxy survey (2014, background): “…effects should be A1, page 8 of 18 most clearly seen for intrinsically flat disc-dominated galaxies, we separated the MS into early and late types by their concentration indices c ≡ r90/r50 in the r band, with the dividing value at c = 2.6 (e.g., Strateva et al. 2001; Lackner & Gunn 2012).”
Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample (2002, background): “That the star/galaxy separation algorithm is not perfect is obvious from the number of extended sources along the branch of latetype stars (r∗ − i∗ > 1), a color that low-redshift galaxies rarely have (Yasuda et al. 2001; Strateva et al. 2001).”
Galaxy luminosities, stellar masses, sizes, velocity dispersions as a function of morphological type (2009, methodology): “In parallel, it has been recognized that relatively simple criteria, using either crude measures of the light profile (e.g. Strateva et al. 2001), the colours (e.g. Baldry et al. 2004) or some combination of photometric and spectroscopic information (Bernardi et al. 2003; Hyde & Bernardi 2009),…”
The Broadband Optical Properties of Galaxies with Redshifts 0.02 < z < 0.22 (2002, neutral): “This result corresponds closely to the work of Strateva et al. (2001), which found a double peaked distribution of (observer-frame) u r color.”
Present-Day Growth of Black Holes and Bulges: The Sloan Digital Sky Survey Perspective (2004, background): “Shimasaku et al. (2001) and Strateva et al. (2001) show that there is a good correspondence between C and Hubble type, with C 2:6 marking the boundary between early-type galaxies (E, S0, and Sa) and late-type systems (Sb Irr).”
The DEEP2 Galaxy Redshift Survey: the relationship between galaxy properties and environment at z∼ 1 (2006, background): “A distinct bimodality exists in the colour distribution with a division at (U − B)0 ∼ 1.0, separating members of the ‘blue cloud’ from red-sequence galaxies (e.g. Strateva et al. 2001; Baldry et al. 2004; Bell et al. 2004; Weiner et al. 2005).”
The DEEP2 galaxy redshift survey: evolution of the colour–density relation at 0.4 < z < 1.35 (2006, background): “…out to z ∼ 1 is found to be effectively described as a combination of two distinct galaxy types: red, early–type galaxies lacking much star formation and blue, late–type galaxies with active star formation (e.g., Strateva et al. 2001; Baldry et al. 2004; Bell et al. 2004; Menanteau et al. 2006).”
Galaxy and Mass Assembly (GAMA): ugriz galaxy luminosity functions (2011, background): “Although colour bimodality is more pronounced in (u − r) colour, e.g. Strateva et al. (2001), Baldry et al. (2004), u-band photometry, even after forming a ‘pseudo-Petrosian’ magnitude (equation 1) is rather noisy, and so we prefer to base our colour cuts on the more robust (g − r) colour.”
The Luminosity Function of Morphologically Classified Galaxies in the Sloan Digital Sky Survey (2002, background): “Shimasaku et al. (2001) report that this C parameter shows the strongest correlation with visually-classified morphology among simple photometrically-defined parameters (see also, Doi, Fukugita & Okamura 1993; Abraham et al. 1994; Blanton et al. 2001; Strateva et al. 2001; Bernardi et al. 2002b).”
Illuminating Low Surface Brightness Galaxies with the Hyper Suprime-Cam Survey (2017, background): “Colors The optical colors of galaxies reveal their dominant stellar populations and thus correlate strongly with galaxy morphology, leading to the well-known separation of galaxies into red and blue sequences (e.g., Strateva et al. 2001; Blanton & Moustakas 2009).”
On the Origin of [O II] Emission in Red-Sequence and Poststarburst Galaxies (2005, methodology): “…diving into line comparisons, we recall that the color distribution of galaxies is highly bimodal, as has been shown repeatedly (e.g., Strateva et al. 2001; Hogg et al. 2002; Blanton et al. 2003b; Baldry et al. 2004; Bell et al. 2004; Weiner et al. 2005; Willmer et al. 2006;…”
Characterizing the Fast Radio Burst Host Galaxy Population and its Connection to Transients in the Local and Extragalactic Universe (2021, background): “The late-type galaxies with ongoing star formation and, therefore, young stellar populations lie in the “blue cloud”, i.e., blue galaxies (Strateva et al. 2001), while massive early-type galaxies live in the “red and dead” zone characterized by very low star formation and hence older stellar…”