A Survey of Three Isotopologues of CO in Molecular Clouds in the CMa OB1 Complex

Abstract

Using the Purple Mountain Observatory 13.7 m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous survey of 12CO, 13CO, and C18O (J = 1–0) toward the CMa OB1 complex with a sky coverage of 16.5 deg2 (221.5° ≤ l ≤ 227°, −2.5° ≤ b ≤ 0.5°). Emission from the CMa OB1 complex is found in the range 7 km s−1 ≤ VLSR ≤ 25 km s−1. The large-scale structure, physical properties, and chemical abundances of the molecular clouds are presented. A total of 83 C18O molecular clumps are identified with the GaussClumps algorithm within the mapped region. We find that 94% of these C18O molecular clumps are gravitationally bound. The relationship between their size and mass indicates that none of the C18O clumps has the potential to form high-mass stars. Using a semiautomatic IDL algorithm, we newly discover 85 CO outflow candidates in the mapped area, including 23 bipolar outflow candidates. Additionally, a comparative study reveals evidence for a significant variety of physical properties, evolutionary stages, and levels of star formation activity in different subregions of the CMa OB1 complex.