Astronomy & Astrophysics

Free access article

Issue		A&A Volume 376, Number 3, September IV 2001
Page(s)		751 - 755
Section		Cosmology
DOI		10.1051/0004-6361:20010861

A&A 376, 751-755 (2001)
DOI: 10.1051/0004-6361:20010861

Deuterium at high redshift: Primordial or evolved?

N. Prantzos¹ and Y. Ishimaru^{1, 2}

¹ Institut d'Astrophysique de Paris, 98bis Bd. Arago, 75014 Paris, France
² Department of Astronomy, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
e-mail: ishimaru@iap.fr

(Received 14 May 2001 / Accepted 13 June 2001)

Abstract
On the basis of arguments from galactic chemical evolution we suggest that the recent observations of D/H vs. metallicity in several high redshift absorbers are best understood if the primordial D value is in the range $D_{\rm P}/H\sim2{-}3\times 10^$ . This range points to a rather high baryonic density ( $\Omega_{\rm B}h^2=0.019{-}0.026$ ) compatible to the one obtained by recent estimates based on the Cosmic Microwave Background (CMB) anisotropy measurements. Slightly higher values ( $D/H\sim4\times 10^$ ) are found in Lyman limit systems. Such values are still compatible with CMB estimates but, if taken at face value, suggest a trend of decreasing D abundance with metallicity. We argue that special assumptions, like differential enrichment, are required to explain the data in that case. A clear test of such a differential enrichment would be an excess of products of low mass stars like C and/or N in those systems, but currently available data of N/Si in DLAs do not favour such a "non-standard" scenario.

Key words: cosmology -- galaxies: abundances -- galaxies: evolution

Offprint request: N. Prantzos, prantzos@iap.fr

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