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Astron. Astrophys. 355, L1-L4 (2000)

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Letter to the Editor

On the deuterium abundance at za = 3.514 towards APM 08279+5255 *

S.A. Levshakov **  1, I.I. Agafonova **  1 and W.H. Kegel 2

1 European Southern Observatory, 85748 Garching bei München, Germany
2 Institut für Theoretische Physik der Universität Frankfurt am Main, 60054 Frankfurt/Main 11, Germany

Received 15 November 1999 / Accepted 28 January 2000

Abstract

A very low primordial deuterium abundance of [FORMULA] has recently been proposed by Molaro et al. in the Lyman limit system with [FORMULA] cm-2 at [FORMULA] towards the quasar APM 08279+5255. The D/H value was estimated through the standard Voigt fitting procedure utilizing a simple one-component model of the absorbing region. We have investigated this system using our new Monte Carlo inversion procedure which allows us to recover self-consistently both the physical parameters of the gas cloud and the projected velocity and density distributions along the line of sight. The absorption lines of H I , C II , C IV , Si III , and Si IV were analyzed simultaneously. The result obtained shows a considerably lower neutral hydrogen column density [FORMULA] cm-2. Hence, the measurement of the deuterium abundance in this system is rather uncertain. We find that the asymmetric blue wing of the hydrogen Ly[FORMULA] absorption is readily explained by H I alone. Thus, up to now, deuterium was detected in only four QSO spectra (Q 1937-1009, Q 1009+2956, Q 0130-4021, and Q 1718+4807) and all of them are in concordance with [FORMULA].

Key words: line: formation – line: profiles – galaxies: quasars: absorption lines – galaxies: quasars: individual: APM 08279+5255

* Based on data obtained at the W. M. Keck Observatory, which is jointly operated by the California Institute of Technology, the University of California and the National Aeronautics and Space Administration.
** On leave from the Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg

Send offprint requests to: S.A. Levshakov

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© European Southern Observatory (ESO) 2000

Online publication: March 17, 2000
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