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M. S. Sahu (NASA/GSFC & CUA), W. Landsman (SSAI), F.C. Bruhweiler (CUA), J. Holberg (U Arizona), I. Hubeny (NASA/GSFC), M. Barstow (U Leicester), J. Linsky (U Colorado), T. Gull (NASA/GSFC), D. Lindler (Sigma/GSFC), T. Lanz (U Maryland), K. Feggans (Sigma/GSFC)
Variations of the D/H ratio on scales of 100 pc are important for two reasons: (1) they complicate the use of deuterium as a cosmological probe, and (2) they imply non-uniform deuterium production/destruction and an inefficient mixing of interstellar gas. The Local Interstellar Medium (LISM) is an ideal location to test whether the D/H abundance ratio varies or not, because the heating sources and radiation fields are well-studied and we have a detailed knowledge of the three-dimensional (3D) structure of the diffuse clouds in the LISM. This detailed knowledge of the number, structure and velocities of the absorbing clouds greatly helps in reducing errors in the derived D/H ratios.
We are working on a project to obtain high-precision D/H abundance ratios in the interstellar gas within 100 pc. For this purpose, we primarily use HST-STIS data towards nearby hot, white dwarfs (WDs). We have also begun an HST archival research project to study about 20 WD sightlines. In this poster, we present new STIS observations for GD 153 and HZ 43 and report the results of our HST Archival project.