Large-scale Mapping of CO Emission in the NGC 6334 Region

The image below shows the distribution of C18O J=2-1 emission within the large star-forming region NGC6334 in Scorpius (at l = 351.2, b = 0.5) at a distance of about 1700 parsec. The CO emission has been integrated over the narrow velocity range of -3.5 to -1.5 km/sec to show to good effect one particular feature, the narrow ridge of molecular gas running from top left to bottom right.

This map and a number of others were made of NGC6334 with the JCMT using the spectral line raster mapping technique, in which the telescope continuously scans along a line of constant Declination while sampling the data every few seconds. The sample rate was 2 seconds in this case, and there are more than 4000 spectra in this map. These data illustrate the power of the technique, and its value to global investigations of large molecular clouds. Sections of this complex have been studied previously in some detail in various molecular lines, but this is the first such map of the entire complex with high angular resolution (about 21 arcsec, as indicated by the symbol at the lower left). In the image shown, an unexpected feature is a remarkably narrow ridge of emission, nearly continuous over the entire complex (i.e., about 7.5 pc in length).

An 800 mm continuum map made by Sandell and Baas, which covers only the top 40% of this map, shows that the narrow ridge also contains dust emission. On the basis of a large body of published data, the NGC6334 complex contains five major sites of star formation activity, which are aligned roughly with the molecular ridge. NGC6334 appears also to be a region where sequential star formation has occurred. The sites in the southwest (lower right) appear to be the oldest, and those at the top, the youngest and apparently still ongoing. The active star-forming sites in the north (NGC6334I, I(N), II) lie somewhat to the east of the molecular ridge, while the southernmost (NGC6334V) lies to the west of it. The bright knot of emission at the southern end of the molecular ridge corresponds with NGC6334IV. One of the goals in this project is to study the properties of these sites as seen in their CO and CS emissions.

H.E.Matthews, JAC & Herzberg Insitute of Astrophyics, NRCC, W.H. McCutcheon, University of British Columbia, G.J.White, Queen Mary and Westfield College, London