A survey of CO and its isotope lines for possible cloud-cloud collision candidates

In the 12CO (J=1-0) survey for the 1331 cold IRAS sources 214 sources show profiles with multiple-peak profiles and are selected as cloud-cloud collision candidates. In January 2005, 201 sources are detected with 12CO(1-0), 13CO(1-0), and C18O(1-0) emission by the 13.7m telescope at Purple Mount Observatory. This is the first CO and its isotope lines directed toward possible cloud-cloud collision regions. According to the statistics of the 201 sources in Galactic distribution, the 201 sources show a similar distribution to the parent sample (1331 cold IRAS sources). These sources are located over a wide range of the Galactocentric distances, and are partly associated with the star formation region. Based on preliminary criteria which describe the spectrum properties of the possible cloud-cloud collision region, the 201 sources are classified into four types by the fit of the spectral profiles between the optically thick and thin lines toward each source. The survey is focused on the possible cloud-cloud collision regions, and gives some evidences to help us with selecting the target region. Then we will carry on the mapping and multi-wavelength study for the selected region in future.