33.8 GHz CCS survey of molecular cores in dark clouds

Shih Ping Lai, Richard M. Crutcher

Research output: Contribution to journalArticle

Abstract

We have conducted a survey of the CCS JN = 32-21 line toward 11 dark clouds and star-forming regions at 30″ spatial resolution and 0.054 km s-1 velocity resolution. CCS was detected only in quiescent clouds, not in active star-forming regions. The CCS distribution shows remarkable clumpy structure, and 25 clumps are identified in seven clouds. Seven clumps with extremely narrow nonthermal line widths (<0.1 km s-1) are among the most quiescent clumps ever found. The CCS clumps tend to exist around the higher density regions traced by NH3 emission or submillimeter continuum sources, and the distribution is not spherically symmetric. Variation of the CCS abundance was suggested as an indicator of the evolutionary status of star formation. However, we can only find a weak correlation between N(CCS) and nH2,vir. The velocity distributions of CCS clouds reveal that a systematic velocity pattern generally exists. The most striking feature in our data is a ring structure in the position-velocity diagram of L1544 with an well-resolved inner hole of 0.04 pc x 0.13 km s-1 and an outer boundary of 0.16 pc x 0.55 km s-1. This position-velocity structure clearly indicates an edge-on disk or ring geometry, and it can be interpreted as a collapsing disk with an infall velocity ≳0.1 km s-1 and a rotational velocity less than our velocity resolution. Nonthermal line width distribution is generally coherent in CCS clouds, which could be evidence for the termination of Larson's Law at small scales, ∼0.1 pc.

Original languageEnglish (US)
Pages (from-to)271-286
Number of pages16
JournalAstrophysical Journal, Supplement Series
Volume128
Issue number1
DOIs
StatePublished - May 1 2000

Keywords

  • Ism: Clouds
  • Ism: Kinematics and dynamics
  • Ism: Molecules
  • Radio lines : Ism
  • Surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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