Measurements of far-UV emission from elliptical galaxies at z=0.375

被引:25
作者
Brown, TM
Ferguson, HC
Deharveng, JM
Jedrzejewski, RI
机构
[1] NASA, Astron & Solar Phys Lab, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[2] Space Telescope Sci Inst, Baltimore, MD 21218 USA
[3] CNRS, Astron Spatiale Lab, F-13376 Marseille 12, France
基金
美国国家航空航天局;
关键词
galaxies : abundances; galaxies : evolution; galaxies : stellar content; ultraviolet : galaxies; ultraviolet : stars;
D O I
10.1086/311743
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The "UV upturn" is a sharp rise in spectra of elliptical galaxies shortward of rest-frame 2500 Angstrom. It is a ubiquitous phenomenon in nearby giant elliptical galaxies and is thought to arise primarily from low-mass evolved stars on the extreme horizontal branch and beyond. Models suggest that the UV upturn is a very strong function of age for these old stellar populations, increasing as the galaxy gets older. In some models, the change in UV/optical flux ratio is a factor of 25 over timescales of less than 3 Gyr. To test the predictions for rapid evolution of the UV upturn, we have observed a sample of normal elliptical galaxies in the z = 0.375 cluster Abell 370 with the Faint Object Camera aboard the Hubble Space Telescope. A combination of two long-pass filters was used to isolate wavelengths shortward of rest-frame 2700 Angstrom, providing a measurement of the UV upturn at a lookback time of approximately 4 Gyr. Surprisingly, the four elliptical galaxies observed show a range of UV upturn strength that is similar to that seen in nearby elliptical galaxies, with an equivalent m(1550) - V color ranging from 2.9 to 3.4 mag. Our result is inconsistent with some models for the UV upturn; other models are consistent only for a high redshift of formation (z(f) greater than or equal to 4).
引用
收藏
页码:L139 / L142
页数:4
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