1995A&A...303..901T

The core of the W 3 molecular cloud has been mapped in a 3'x2' region in the J=2-1 transition of C¹⁸O and the J=3-2 and J=5-4 transitions of C³⁴S with angular resolutions of 11", 17" and 10", respectively, using the IRAM 30-m telescope. The W 3 core consists of two regions separated by 75" (=0.85pc at 2.3kpc). The region associated with W 3 IRS 5 has an average v_lsr≃-39km/s and a mass of 800M_☉. The other, more extended region associated with W 3 IRS 4 has an average v_lsr≃-43km/s and a mass of 1500M_☉. The IRS 4 region is resolved into four smaller clumps. One of these is close to, but not coincident with, the submillimeter continuum peak SMS 3; another is very close to IRS 4 and SMS 2. The IRS 5 region is barely resolved into four clumps. There is a clump centered on IRS 5. From the C¹⁸O data, the H₂ column densities of the clumps have been determined. From a Large Velocity Gradient analysis of the C³⁴S 3-2/5-4 ratios the H₂ densities and masses were estimated; these are compared with general results from the virial theorem. Dynamics are investigated using velocity channel maps. Over a 70" region in Declination, the v_lsr of the IRS 4 region changes from -42km/s in the southern part to -46km/s in the northern part. For the northern part of IRS 4, over 70" in Right Ascension, there is a change from -41km/s in the western part to -47km/s in the eastern part. This velocity change is opposite to the sense of galactic rotation; the gradient is 9km/s/pc. For the IRS 5 region, there is a similar change in v_lsr with Dec., but only a small change with R.A. Considering the presence of a magnetic field of 100µG towards IRS 4 and the striking change in radial velocity, we speculate that "magnetic braking" dominates the dynamics in the IRS 4 region. Our C¹⁸O and C³⁴S results are compared with the abundances of other molecular species and show that the IRS 4 and IRS 5 regions have distinctly different chemistry.