We have presented plots of the galactic distribution of Na I interstellar absorption for lines-of-sight 300 pc using data originally presented in Welsh et al. (1994) together with the newly determined distances of the Hipparcos satellite. Four main differences in the distribution of neutral gas in the LISM have been found. Firstly, no regions of dense neutral absorption (log 11.0 cm-2 have been found for lines-of-sight 50 pc. This central (neutral gas-free) Local Bubble cavity is typically of radius 70 pc in most galactic directions, and is thus 50% larger than previously thought. Secondly, the extremely low neutral gas density interstellar tunnel towards the star CMa is almost twice as wide as previously determined, and thirdly a similarly tenous interstellar tunnel feature has been identified in the general direction of Lupus-Norma extending to at least 170 pc. Finally, we tentatively suggest that the galactic direction of = is also deficient of neutral gas out to a distance of at least 100 pc.
© European Southern Observatory (ESO) 1998
Online publication: April 15, 1998