Mathematics – Logic
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997hst..prop.7292b&link_type=abstract
HST Proposal ID #7292
Mathematics
Logic
1
Hst Proposal Id #7292 Quasar Absorption Lines
Scientific paper
The Primordial D/H ratio is the most sensitive measure of the baryon to photon ratio, a fundamental cosmological number, with wide ranging uses. It should be possible to measure the primordial cosmological D/H ratio in gas clouds towards QSOs with very low metal abundances. Seven results are in the literature, but there is stark disagreement in the D/H values which are obtained in some of the best cases. Workers do not agree on the origin of the differences, but a major factor is contamination of the D absorption line by H. The only decisive way to resolve this is to observe additional gas clouds. The HST allows us to look at lower redshifts than those in the literature. Gas clouds at low redshift should give dramatically cleaner results because the Lyman-a forest is much thinner, and the gas velocity structure is often much simpler. We propose STIS spectra of seven QSOs each of which could yield a new measurement of D/H. In two cases the data from this cycle should suffice, but for the others we would request additional spectra later. We need many more measures to understand and correct systematic errors, and we need HST observations of low redshift gas which suffers much less contamination by H.
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