Science with the Galaxy Evolution Explorer : Starbursts and Stellar Populations

Abstract

The Galaxy Evolution Explorer was launched in April 2003 and has returned wide field UV imagery in a far UV (1450A) and near UV (2800A) channel. We report on new results in the study of starbursts and stellar populations. Galex detects light from recently formed massive stars, and also from hot evolved older stars. Combining SDSS and Galex photometry gives a large multiwavelength dataset. Fitting the SEDs to population models in a statistical sense gives constraints on the starburst history of galaxies. Galex is remarkably sensitive to low levels of star formation, some of which is detected in the red sequence of ellipticals and bulges, even to 10^–3 M_⊙ yr^–1. The UV rising flux is clearly seen in nearby bulges and elliptical, and is also detected to z~ 0.1 in A2670. Constructing a sample of ellipticals selected from SDSS to lack emission lines to appear in all respects “old, red, and dead” we find no correlation between the UV rising flux and the Lick Mg₂ index, or with any other measurable parameter such as velocity dispersion; this finding contradicts some earlier studies.

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