Volume 382, Number 2, FebruaryI 2002
|Page(s)||624 - 638|
|Published online||15 February 2002|
Radio-millimetre investigation of galactic infrared dark clouds*
Laboratoire de radioastronomie millimétrique, URA 336 du CNRS, École normale supérieure et Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France
Corresponding author: D. Teyssier, email@example.com
Accepted: 13 November 2001
We present follow-up observations of the mid-Infrared dark clouds selected from the ISOGAL inner Galaxy sample. On-the-fly maps of 13CO, C18O and the 1.2 mm continuum emission were conducted at the IRAM 30-m telescope, showing spectacular correlation with the mid-IR absorption. The dark clouds are distributed as far as the prominent molecular ring at a distance of 3 to 7 kpc from the Sun. The clouds exhibit shapes ranging from globules to thin filaments down to 1 pc in size. The on-the-fly images obtained in 13CO and C18O confirmed that the cores are dense, compact molecular emitters, significantly more massive than local dark clouds (more than 1000 ) and lie within low activity Giant Molecular Clouds (GMC's). Ratios of the emission in the and transitions of 13CO and C18O show a remarkable uniformity within each cloud, with a significant portion of the sample represented well by a ratio of . Preliminary analysis of temperature and density measurements reveals that most of the cores have densities above 105 cm-3 and temperatures between 8 and 25 K, these latter clouds being associated with young embedded stars. Despite the high extinction inferred from mid-IR (, Hennebelle et al. [CITE]), the molecular lines are surprisingly weak, indicating likely depletion onto cold grains.
Key words: ISM: clouds / molecules / structure / radio continuum: ISM / radio lines: ISM
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.