1999/11/15 by S. A. Levshakov, Levshakov, S. A., I. I. Agafonova +3
Physics and Astronomy · #Astrophysics (astro-ph) #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #Nuclear physics research studies #Particle physics theoretical and experimental studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9911261
4 pages, 3 ps figures, l-aa.sty file, submitted to Astron. Astrophys. Letters
arxiv created 1999/11/15 · openalex publication_date 1999/11/15 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A very low primordial deuterium abundance of D/H = 1.5 10-5 has recently been proposed by Molaro et al. in the Lyman limit system with log(NHI) = 18.1 cm-2 at za = 3.514 towards the quasar APM08279+5255. The D/H value was estimated through the standard Voigt fitting procedure utilizing a simple one-component model of the absorbing region. The authors assumed, however, that `a more complex structure for the hydrogen cloud with somewhat ad hoc components would allow a higher D/H'. We have investigated this system using our new Monte Carlo inversion procedure which allows us to recover not only the physical parameters but also the velocity and density distributions along the line of sight. The absorption lines of HI, CII, CIV, SiIII, and SiIV were analyzed simultaneously. The result obtained shows a considerably lower neutral hydrogen column density log(NHI) = 15.7 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-alpha absorption is readily explained by HI alone. Thus, up to now, deuterium was detected in only four QSO spectra (Q1937-1009, Q1009+2956, Q0130-4021, and Q1718+4807) and all of them are in concordance with D/H = 4 10-5.