A search for massive dense cores with CO J = 1-0 line^*

Astronomy Department, CAS-PKU Joint Beijing Astrophysics Center, Peking University, Beijing 100871, PR China

Corresponding author: Y. Wu, ywu@vega.bac.pku.edu.cn

Received: 31 January 2001
Accepted: 15 October 2001

Abstract

This paper reports ¹³CO -0 line observations toward 107 IRAS or H₂O maser sources with the 13.7 m telescope of the Purple Mountain Observatory (PMO). Parameters of emission components are obtained and the profile characteristics are identified. For all the components, kinematic distances are derived. The bolometric luminosities of the corresponding IRAS sources are calculated for 95 sources, all of which are larger than 10³ . We also mapped eight sources. Results show that there are cores in the clouds. The sizes of the cores are about 1~3 pc, much greater and more extensive than those of cores in dark clouds. The hydrogen densities are ~10²-10³ cm^-3. Systematic velocity shifts were found in 3 sources. Every mapped core contains one or more IRAS source. Each core has one and only one IRAS source that satisfies the criteria of ultra compact HII (UC HII) regions. For the cores, 2MASS data are available; dozens of 2MASS sources with different color indices and brightness are found within the core.