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Title: THE GALEX/S{sup 4}G UV–IR COLOR–COLOR DIAGRAM: CATCHING SPIRAL GALAXIES AWAY FROM THE BLUE SEQUENCE

We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6 μm photometry for >2000 galaxies, available for 90% of the S{sup 4}G sample. We find a very tight GALEX blue sequence (GBS) in the (FUV–NUV) versus (NUV–[3.6]) color–color diagram, which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale (τ) and a degeneracy between τ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the GALEX green valley (GGV). At the red end of the GBS, at (NUV–[3.6]) > 5, we find a wider GALEX red sequence (GRS) mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by M{sub [3.6]}) since both massive (M{sub ⋆}>10{sup 11}M{sub ⊙}) blue- and red-sequence galaxies are identified. The type that is proportionally more often found in the GGV is the S0-Sa’s, and most of these are located in high-density environments. We discuss evolutionary models of galaxies that show a rapid transition from the blue to the red sequence onmore » a timescale of 10{sup 8} yr.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ; ;  [8]
  1. Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
  2. Aix Marseille Université, CNGRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France)
  3. European Southern Observatory, Casilla 19001, Santiago 19 (Chile)
  4. National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
  5. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
  6. Astronomy Division, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland)
  7. Kapteyn Astronomical Institute, Postbus 800, NL-9700 AV Groningen (Netherlands)
  8. Instituto de Astrofísica de Canarias, Vía Láctea, S/N, E-38205 La Laguna (Spain)
Publication Date:
OSTI Identifier:
22364173
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 800; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COLOR; COSMIC DUST; COSMOLOGICAL MODELS; DENSITY; DIAGRAMS; GALACTIC EVOLUTION; GALAXIES; MASS; PHOTOMETRY; STAR EVOLUTION; STARS