The structure and kinematics of dense gas in NGC 2068

S. L. Walker-Smith*, J. S. Richer, J. V. Buckle, R. J. Smith, J. S. Greaves, I. A. Bonnell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

We have carried out a survey of the NGC 2068 region in the Orion B molecular cloud using HARP on the James Clerk Maxwell Telescope, in the (CO)-C-13 and (CO)-O-18 (J = 3-2) and (HCO+)-C-13 (J = 4-3) lines. We used (CO)-C-13 to map the outflows in the region, and matched them with previously defined Submillimetre Common-User Bolometer Array cores. We decomposed the (CO)-O-18 and (HCO+)-C-13 into Gaussian clumps, finding 26 and eight clumps, respectively. The average deconvolved radii of these clumps are 6200 +/- 2000 and 3600 +/- 900 au for (CO)-O-18 and (HCO+)-C-13, respectively. We have also calculated virial and gas masses for these clumps, and hence determined how bound they are. We find that the (CO)-O-18 clumps are more bound than the (HCO+)-C-13 clumps (average gas mass to virial mass ratio of 4.9 compared to 1.4). We measure clump internal velocity dispersions of 0.28 +/- 0.02 and 0.27 +/- 0.04 km s(-1) for (CO)-O-18 and (HCO+)-C-13, respectively, although the (HCO+)-C-13 values are heavily weighted by a majority of the clumps being protostellar, and hence having intrinsically greater linewidths. We suggest that the starless clumps correspond to local turbulence minima, and we find that our clumps are consistent with formation by gravoturbulent fragmentation. We also calculate interclump velocity dispersions of 0.39 +/- 0.05 and 0.28 +/- 0.08 km s(-1) for (CO)-O-18 and (HCO+)-C-13, respectively. The velocity dispersions (both internal and external) for our clumps match results from numerical simulations of decaying turbulence in a molecular cloud. However, there is still insufficient evidence to conclusively determine the type of turbulence and time-scale of star formation, due to the small size of our sample.

Original languageEnglish
Pages (from-to)3252-3265
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume429
Issue number4
DOIs
Publication statusPublished - Mar 2013

Keywords

  • stars: formation
  • ISM: clouds
  • ISM: individual objects: NGC 2068
  • MOLECULAR CLOUDS
  • STAR-FORMATION
  • ORION-B
  • MAGNETIC-FIELDS
  • SCUBA SURVEY
  • CLUSTERS
  • CORES
  • FRAGMENTATION
  • TURBULENCE
  • COLLAPSE

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