Colors of Ellipticals from GALEX to Spitzer

Abstract

Multi-color photometry is presented for a large sample of local ellipticals selected by morphology and isolation. The sample uses data from GALEX, SDSS, 2MASS and Spitzer to cover the filters NUV, ugri, JHK and 3.6mum. Various two-color diagrams, using the half-light aperture defined in the 2MASS J filter, are very coherent from color to color, meaning that galaxies defined to be red in one color are always red in other colors. Comparison to globular cluster colors demonstrates that ellipticals are *not* composed of a single age, single metallicity (e.g., [Fe/H]) stellar population, but require a multi-metallicity model using a chemical enrichment scenario. Such a model is sufficient to explain two-color diagrams and the color-magnitude relations for all colors using only metallicity as a variable on a solely 12 Gyrs stellar population with no evidence of stars younger than 10 Gyrs. The [Fe/H] values that match galaxy colors range from -0.5 to +0.4, much higher (and older) than population characteristics deduced from Lick/IDS line-strength system studies, indicating an inconsistency between galaxy colors and line indices values for reasons unknown. The NUV colors have unusual behavior signaling the rise and fall of the UV upturn with elliptical luminosity. Models with BHB tracks can reproduce this behavior indicating the UV upturn is strictly a metallicity effect.

60 pages, 17 figures, 4 tables, accept by AJ

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• On the Properties of Spectroscopically-Confirmed Ultra-Diffuse Galaxies Across Environment
• Young, metal-enriched cores in early-type dwarf galaxies in the Virgo cluster based on colour gradients
• Galaxy And Mass Assembly (GAMA): Defining Passive Galaxy Samples and Searching for the UV Upturn
• Stellar population synthesis models with a physically varying IMF
• Colors of Dwarf Ellipticals from GALEX to WISE
• Evolution of the Ultraviolet Upturn at $0.3<z<1$: exploring helium rich stellar populations
• The baryonic mass-size relation of galaxies. II. Implications for the evolutionary paths between star-forming and passive galaxies
• Quantifying the Poor Purity and Completeness of Morphological Samples Selected by Galaxy Colour
• UV bright red-sequence galaxies: a comparative study between UV upturn and UV weak systems