Deuterium at high redshift: Primordial or evolved?

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

Corresponding author: N. Prantzos, prantzos@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 vs. metallicity in several high redshift absorbers are best understood if the primordial D value is in the range . This range points to a rather high baryonic density () compatible to the one obtained by recent estimates based on the Cosmic Microwave Background (CMB) anisotropy measurements. Slightly higher values () 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.