High-Resolution Studies of Diffuse Interstellar Gas
Abstract
We describe two recent projects undertaken at McDonald Observatory whose success required high-resolution measurements. First high-resolution spectra revealed a 7Li/6Li ratio of about 2 in gas toward o Persei a value consistent with expectations of Galactic cosmic ray spallation but much lower than the meteoritic value (12.3). In order to probe the extent in the variation of this ratio we performed an ultra-high-resolution survey. The line of sight toward o Per remains the only one with an isotope ratio different from the meteoritic value but this sight line shows no other indication of an enhanced Li abundance. Second through a high-resolution study of gas seen toward stars in rho Oph Cep OB2 and Cep OB3 we gleaned information about the structure of the diffuse material along the line of sight. Line widths (b-values) and column densities yielded the various distributions among species for individual velocity components. For instance CN resides in the densest central portion of a diffuse cloud while Ca+ is much more widely distributed. Moreover gas containing CH arises from two sources: CH associated with dense gas containing CN and CH arising from the synthesis of CH+ in less dense material.
- Publication:
-
IAU Joint Discussion
- Pub Date:
- 2003
- Bibcode:
- 2003IAUJD..20E..10F