The relation between CO J = 2–1 line width in molecular clouds and bolometric luminosity of associated IRAS sources^*

¹ Department of Astronomy, School of Physics, Peking University, Beijing 100871, PR China e-mail: kwang@cfa.harvard.edu; yfwu@bac.pku.edu.cn
² Department of Atmospheric Sciences, School of Physics, Peking University, Beijing 100871, PR China
³ Institut für Anorganische Chemie, Universität Bonn, Römer St. 164, 53117 Bonn, Germany
⁴ I. Physikal. Institut, Universität zu Köln, Zülpicher St. 77, 50937 Köln, Germany

Received: 7 October 2008
Accepted: 21 July 2009

Abstract

Aims. We search for evidence of a relation between properties of young stellar objects (YSOs) and their parent molecular clouds to understand the initial conditions of high-mass star formation.

Methods. A sample of 135 sources was selected from the InfraRed Astronomical Satellite (IRAS) point source catalog, on the basis of their red color to enhance the possibility of discovering young sources. Using the Kölner Observatorium für SubMillimeter Astronomie (KOSMA) 3-m telescope, a single-point survey in ¹³CO  was carried out for the entire sample, and 14 sources were mapped further. Archival mid-infrared (MIR) data were compared with the ¹³CO emissions to identify evolutionary stages of the sources. A ¹³CO observed sample was assembled to investigate the correlation between ¹³CO line width of the clouds and the luminosity of the associated YSOs.

Results. We identified 98 sources suitable for star formation analyses for which relevant parameters were calculated. We detected 18 cores from 14 mapped sources, which were identified with eight pre-UC H ii regions and one UC H ii region, two high-mass cores earlier than pre-UC H ii phase, four possible star forming clusters, and three sourceless cores. By compiling a large (360 sources) ¹³CO observed sample, a good correlation was found between the ¹³CO line width of the clouds and the bolometric luminosity of the associated YSOs, which can be fitted as a power law, lg(ΔV₁₃/ km s^-1) = (-0.023±0.044) + (0.135±0.012)lg. Results show that luminous (>10³ ) YSOs tend to be associated with both more massive and more turbulent (ΔV₁₃ > 2 km s^-1) molecular cloud structures.