Bibcode
DOI
Génova, Ricardo; Beckman, John E.
Bibliographical reference
The Astrophysical Journal Supplement Series, Volume 145, Issue 2, pp. 355-412.
Advertised on:
4
2003
Citations
13
Refereed citations
12
Description
A survey of interstellar Na I D1 and D2 absorption features in the
spectra of 104 early-type stars in the second and third Galactic
quadrants reveals the large-scale kinematics of the interstellar gas
within the Galactic anticenter hemisphere at distances from the Sun
between ~70 and ~250 pc. Employing a technique that uses both the radial
velocities and column densities of the Na I absorptions produced by the
intervening gas we have identified the velocity vectors and determined
the spatial distribution of eight interstellar clouds in the volume
explored. The average internal H I+H2 densities of the clouds
range between 0.03 and 1.7 cm-3, and their masses between 80
and 104 Msolar, although uncertainties in the
sizes of the clouds, their possible extension beyond the region
explored, and the presence of denser gas embedded in the larger clouds
imply that these will tend to be lower limits. We have clearly
identified clumps of denser gas immersed in the low-density gas in one
of the clouds; these clumps show internal H I+H2 densities of
order 50 cm-3. Although we are not able to detect any
interstellar Na I within 70 pc, the sizes of some of the clouds imply
that their near edges are within that range of distances from the Sun.
With respect to the local standard of rest the clouds move with
velocities between 19 and 54 km s-1. Their velocity vectors
do not support the view of a local interstellar medium uniquely
dominated by expansion from centers in the Scorpio-Centaurus OB
association; our results suggest that this expansion is present in the
Galactic center hemisphere but in the Galactic anticenter hemisphere is
restricted to the immediate neighborhood of the Sun.