2000/02/05 by Manuel Peimbert Antonio Peimbert, Peimbert, Manuel Peimbert Antonio
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0002120
10 pages, 1 figure, IAU Symposium 198
arxiv created 2000/02/05 · arxiv updated 2009/12/01
A new determination of the pregalactic helium abundance based on the Magellanic Clouds H II regions is discussed. This determination amounts to Yp = 0.2345 +- 0.0030 and is compared with those derived from giant extragalactic H II regions in systems with extremely low heavy elements content. It is suggested that the higher primordial value derived by other authors from giant H II region complexes could be due to two systematic effects: the presence of neutral hydrogen inside the helium Stromgren sphere and the presence of temperature variations inside the observed volume.