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Centro de Astrofísica da Universidade do Porto

Systematics of the ultraviolet rising flux in a GALEX/SDSS sample of early-type galaxies

M. R. Rich, S. Salim, J. Brinchmann, S. Charlot, M. Seiberg, G. Kauffmann, Y. Lee, S. K. Yi, T. A. Barlow, L. Bianchi, Y. Byun, J. Donas, K. Forster, P. G. Friedman, T. Heckman, P. N. Jelinsky, B. F. Madore, R. F. Malina, C. D. Martin, B. Milliard, P. Morrissey, S. G. Neff, D. Schiminovich, O. H. W. Siegmund, T. Small, A. S. Szalay, B. Y. Welsh, T. K. Wyder

Abstract
We present ultraviolet photometry for a sample of morphologically early-type galaxies selected by matching the Sloan Digital Sky Survey (SDSS) First Data Release with the Galaxy Evolution Explorer (GALEX) Medium and All-sky Imaging Surveys. We obtain a working sample of 1032 early-type galaxies with GALEX far-UV (FUV) detections, SDSS spectroscopy, and z〈0.2. Using the SDSS spectra to identify galaxies with even weak star formation or evidence of active galactic nuclei, and further removing galaxies with any evidence of non-early-type morphology, we derive a final sample of 172 red quiescent early-type galaxies. We find that the FUV-r color has a full range of 5 mag. Plotting the FUV-r color against the metallicity sensitive Lick Mg2 and D4000 indices and against the stellar velocity dispersion, we find no correlation between our measurement of UV rising flux and any parameter sensitive to the global metallicity of quiescent early-type galaxies.

The Astrophysical Journal Letters
Volume 619, Page L107
January 2005

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