Some aspects of the chemical evolution of 4He in the Galaxy: the He/H abundance gradient and the Delta Y/Delta Z enrichment ratio
Abstract
Description
Two aspects of the chemical evolution of 4He in the Galaxy are considered on the basis of a sample of disk planetary nebulae by the application of corrections due to the contamination of 4He from the progenitor stars. First, the He/H radial gradient is analyzed, and then, the helium to heavy element enrichment ratio is determined for metallicities up to the solar value.
10 pages, 5 postscript figures, Latex, uses newpasp.sty, psfig.sty, to be published in the proceedings of IAU Syposium 198, The light elements and their evolution, eds. L. da Silva, M. Spite, J. R. de Medeiros, ASP Conference Series, also available at http://www.iagusp.usp.br/~maciel/
10 pages, 5 postscript figures, Latex, uses newpasp.sty, psfig.sty, to be published in the proceedings of IAU Syposium 198, The light elements and their evolution, eds. L. da Silva, M. Spite, J. R. de Medeiros, ASP Conference Series, also available at http://www.iagusp.usp.br/~maciel/