In order to investigate the origin of the far-UV (FUV) flux from the early-type galaxies, the Galaxy Evolution Explorer is collecting the UV data for the elliptical-rich clusters at moderate redshifts (z < 0.2) where the dominant FUV source is predicted to be hot horizontal-branch (HB) stars and their post-HB progeny. Here we present our first result for the early-type galaxies in A2670 at z = 0.076. Compared to NGC 1399, a nearby giant elliptical galaxy in the Fornax Cluster, it appears that the rest-frame FUV - V color of the giant elliptical galaxies gets redder by ∼0.7 mag at the distance of A2670 (z = 0.076; look-back time ≈ 1.0 Gyr). Although a detailed comparison with the models is postponed until more cluster data are accumulated, it is interesting to note that this value is consistent with the variation predicted by the population synthesis models where the mean temperature of HB stars declines rapidly with increasing look-back time.
Bibliographical noteFunding Information:
GALEX is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. Yonsei University participation is funded by the Korean Ministry of Science and Technology, for which we are grateful. J.-W. L. also acknowledges support from KOSEF to the ARCSEC.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science