Electronic Resource
Palo Alto, Calif.
:
Annual Reviews
Annual Review of Astronomy and Astrophysics
37 (1999), S. 603-648
ISSN:
0066-4146
Source:
Annual Reviews Electronic Back Volume Collection 1932-2001ff
Topics:
Physics
Notes:
Abstract Far-ultraviolet radiation is a ubiquitous, if unanticipated, phenomenon in elliptical galaxies and early-type spiral bulges. It is the most variable photometric feature associated with old stellar populations. Recent observational and theoretical evidence shows that it is produced mainly by low-mass, small-envelope, helium-burning stars in extreme horizontal branch and subsequent phases of evolution. These are probably descendants of the dominant, metal rich population of the galaxies. Their lifetime UV outputs are remarkably sensitive to their physical properties and hence to the age and the helium and metal abundances of their parents. UV spectra are therefore exceptionally promising diagnostics of old stellar populations, although their calibration requires a much improved understanding of giant branch mass loss, helium enrichment, and atmospheric diffusion.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1146/annurev.astro.37.1.603
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