The dense gas component of outflows in the monoceros OB1 dark cloud

Grace A. Wolf-Chase, Christopher K. Walker

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9 Scopus citations


Wolf-Chase, Walker, & Lada (1995, hereafter WWL) found that most of the CS J = 2 → 1 emission in the Mon OB1 dark cloud is concentrated in two regions they refer to as the South Cloud (SCL) and North Cloud (NCL). These regions encompass five of the 10 outflows previously identified in CO by Margulis, Lada, & Snell (1988). The spatial morphologies of the CS J = 5 → 4 and CS J = 7 → 6 emission regions in the SCL (WWL) are significantly different from those of the CS J = 2 → 1 emission. Velocity centroid plots of the CS J = 2 → 1 and CS J = 5 → 4 emission in the line cores indicate that the upper transition primarily traces dense core material, but the lower transition primarily traces dense outflow material. We have found that the CS J = 2 → 1 transition traces a large portion of the dense, low-velocity component of outflows in the Mon OB1 dark cloud. The outflows are identifiable through non-Gaussian, asymmetric wings in the CS J = 2 → 1 lines. This outflow component is not identifiable in CO because the gas in the asymmetric CS line wings is moving at velocities which lie within the core of the much broader CO lines. Two of the outflows which were previously classified as monopolar in CO (Margulis et al. 1988) appear bipolar in CS. We find the mass of this component to be about an order of magnitude greater than previous estimates of the low-velocity outflow component. Comparison of the masses derived for the CS outflows to the masses derived by WWL for the total CS emission in the SCL and NCL indicate that at least 20% of the material in the SCL has been entrained in outflows, and approximately 25%-50% of the material in the NCL is associated with a rotating cloud swept up by an outflow. The addition of the low-velocity CS outflow component to previous estimates of outflow energetics implies that multiple generations of outflows need not be required to support this cloud against collapse. Our results neither support nor rule out the existence of fossil outflows in this cloud. A fully sampled, unbiased survey of the cloud is required to search for such outflows.

Original languageEnglish (US)
Pages (from-to)244-256
Number of pages13
JournalAstrophysical Journal
Issue number1
StatePublished - Jul 1 1995


  • ISM: individual (Monoceros OB1)
  • ISM: jets and outflows
  • ISM: molecules
  • Molecular processes
  • Radio lines: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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