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Published November 1, 2009 | Published
Journal Article Open

Helium Sedimentation and the Ultraviolet Upturn in Brightest Cluster Galaxies

Abstract

Recent observations with the Galaxy Evolution Explorer (GALEX) show strong unexpected ultraviolet (UV) excess in the spectrum of brightest cluster galaxies (BCGs). It is believed that the excess UV signal is produced by old and evolved core-He burning stars, and the UV flux strength could be greatly enhanced if the progenitor stars have a high value of He abundance. In this work, we propose that the sedimentation process can greatly enhance the He abundance in BCGs. Our model predicts that the UV flux strength is stronger in more massive, low-redshift, and dynamically relaxed BCGs. These predictions are testable with the current generation of GALEX+SDSS observations.

Additional Information

© 2009 American Astronomical Society. Received 2009 August 5; accepted 2009 September 30; published 2009 October 12. We thank Sarbani Basu, Thibaut Decressin, Pierre Demarque, Philipp Podsiadlowski, Kevin Schawinski, and Sukyoung Yi for useful discussions. We thank the anonymous referee for helpful comments. This work is supported by Sherman Fairchild Foundation.

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