BIMA 13CO observations of W3

D. A. Roberts, R. M. Crutcher, T. H. Troland

Research output: Contribution to journalArticlepeer-review


The W3 molecular cloud core has been observed with the BIMA and NRAO 12 m telescopes in the 13CO (J = 1-0) and C18O (J = 1-0) lines. Two BIMA fields were imaged, centered on the infrared sources IRS 5 and IRS 4 (80″ west of IRS 5). In order to observe large-scale structure, a full-synthesis cube was made with a resolution of 9″.5 × 8″.0. Additionally, a high-resolution cube was made with only the IRS 5 pointing of BIMA to investigate the distribution of gas near IRS 5 at high angular resolution. The total H2 masses of the molecular cores associated with IRS 4 and IRS 5 are 1700 and 1100 M, respectively. Six clumps are identified. Derived H2 masses of the clumps are between 120 and 480 M, and under simple geometrical assumptions, n(H2) is between 1.8 and 4.5 × 105 cm-3. The virial masses of the clumps are within 30% of the derived H2 masses. For the clumps located at IRS 5 and 20″ south of IRS 4, the 13CO opacities derived were 0.3 and 0.7, respectively. At the positions of IRS 4 and IRS 5, individual clumps are observed; the IRS 4 clump in particular has a n(H2) a factor of 2 larger than the other clumps. At the position of IRS 5, the high-resolution data show a velocity structure suggestive of two clumps, one north and another south of IRS 5. Integrating the emission from these clumps gives an H2 mass of 110 M. Using the derived H2 column density toward IRS 5 and a previous H I Zeeman result, we can derive the ratio |B|/NH (which is proportional to the magnetic flux-to-mass ratio ψB/M). The determined ratio is near the magnetically critical value, which is consistent with the standard theory of high-mass star formation.

Original languageEnglish (US)
Pages (from-to)318-324
Number of pages7
JournalAstrophysical Journal
Issue number1 PART I
StatePublished - 1997


  • ISM: individual (W3)
  • ISM: magnetic fields
  • ISM: molecules
  • Radio lines: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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