  Recent observations with Galaxy Evolution Explorer (GALEX) show strong
unexpected 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 high value of He abundance. In this work, we propose that
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.
