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The deuterium abundance in the z= 0.7 absorber towards QSO PG1718+4807 |
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| Authors: | N H M Crighton J K Webb R F Carswell K M Lanzetta |
| Institution: | School of Physics, University of New South Wales, Sydney NSW 2052, Australia;Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA;Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY 11794, USA |
| Abstract: | We report on a further analysis of the ratio of deuterium to hydrogen (D/H) using Hubble Space Telescope ( HST ) spectra of the z = 0.701 Lyman limit system towards the quasi-stellar object (QSO) PG1718+481. Initial analyses of this absorber found it gave a high D/H value, 1.8– 3.1 × 10 Tytler et al. commented on the first analysis of Webb et al., reporting the presence of a contaminating lower redshift Lyman limit system, with log N (H i )] = 16.7 at z = 0.602 , which biases the N (H i ) estimate for the main system. Here we show that this absorber actually has log N (H i )] < 14.6 and does not impact on the estimate of N (H i ) in the system of interest at z = 0.701 . The purpose of the present paper is to highlight important aspects of the analysis which were not explored in previous studies, and hence to help refine the methods used in future analyses of D/H in quasar spectra. |
| Keywords: | nuclear reactions nucleosynthesis abundances quasars: absorption lines cosmological parameters |