Open AccessInterstellar Na i D lines towards the Southern Coalsack
Author(s) -
Franco G. A. P.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03434.x
Subject(s) - physics , astrophysics , stars , spectral line , line of sight , interstellar medium , absorption (acoustics) , interstellar cloud , line (geometry) , radial velocity , molecular cloud , absorption spectroscopy , astronomical spectroscopy , emission spectrum , astronomy , galaxy , optics , geometry , mathematics
The interstellar Na i D absorption‐line profiles observed for 15 stars with lines of sight towards the Southern Coalsack are analysed. The method of profile fitting was used in an attempt to determine column densities, linewidths and velocities for the individual interstellar clouds contributing to the observed absorption lines. In common, the observed spectra show a prominent component which is probably associated with the nearest absorbing material composing the Coalsack. The obtained spatial velocity distribution shows great similarity with earlier results from CO emission. In addition, the Na i D data reveal evidence for the existence of two or three other structures with radial velocities of about −22, −33 and −40 km s −1 . Such components may be the counterparts of interstellar structures observed in diffuse H α and CO emission. The assumption that at least one of these components originated in the Carina arm imposes ∼0.9–1.0 kpc as the maximum distance to the near side of that arm.