Local Interstellar Medium and D/h Ratio -- Cycle 2

Details Local Interstellar Medium and D/h Ratio -- Cycle 2 Local Interstellar Medium and D/h Ratio -- Cycle 2

Jul 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992hst..prop.3943l&link_type=abstract

HST Proposal ID #3943

Mathematics

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Hst Proposal Id #3943

Scientific paper

We will observe with 20,000 spectral resolution the stellar Lyman alpha emission line and interstellar hydrogen and deuterium absorption towards local late-type stars to derive the H and D column densities and D/H ratios along different lines of sight. High resolution (90,000) spectra of the MgII and FeII lines will help determine the interstellar line broadening and whether material along each line of sight has more than one velocity component. This is critical for accurate measurements of D/H, because both the D and H lines are on or near the flat part of the curve of growth. Previous IUE and Copernicus observations, which had low signal/noise and inadequate spectral resolution, provided very crude D/H values and suggested that the D/H ratio may vary within a few parsecs of the Sun. We will measure D/H with at least one order of magnitude improved precision and determine whether the proposed local variations are real. The local value(s) of D/H may be extrapolated to zero metal abundance to estimate the primordial value, which is valuable for constraining cosmological models.

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