1997/01/21 by Ben Dorman, Dorman, Ben
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9701157
9 pages, LaTeX + 1 encapsulated ps figure, uses cupconf.sty (version included). To appear in Advances in Stellar Evolution, eds. R. T. Rood & A. Renzini. Available also at http://www.astro.virginia.edu/~bd4r/
arxiv created 1997/01/21 · openalex publication_date 1997/01/21 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Since the discovery of the Ultraviolet Upturn Phenomenon (``UVX'') in early-type galaxies it has been clear that the stellar populations of such systems contain an unexpected hot component. Recent work has provided strong circumstantial evidence that the stars radiating at short wavelengths (< 2000 Angstrom) is in fact due to hot horizontal branch, post-HB stars and post-AGB stars. We summarize the arguments in favour of this hypothesis. We then derive an estimate for the fraction of all HB stars that must be contributing to the UV upturn phenomenon in the strongest UVX galaxy, NGC 1399, and derive a hot star fraction fH ~ 0.16.The implication is that UVX arises from a minority fraction of the dominant stellar population. We conclude that the mechanism that produces the UVX is not one that can be explained naturally by the presence of an extremely metal-rich or metal-poor population.