2014MNRAS.443.2264L

The physical, chemical and kinetic characteristics of 12 northern infrared dark clouds (IRDCs) are systematic studied using the 13CO (1-0) and C18O (1-0) lines, observed with the Purple Mountain Observatory 13.7 m radio telescope, the 1.1 mm Bolocam Galactic Plane Survey data and Galactic Legacy Infrared Mid-Plane Survey Extraordinaire Spitzer Infrared Array Camera 8µm data. The molecular lines emission and 1.1 mm continuum emission almost coincide in morphology for each IRDC and both are associated well with the IRDCs. 10 IRDCs present the filamentary structure and substructures. Totally, 41 IRDC cores are identified, and a statistic research for them shows that the northern IRDC cores have a typical excitation temperature of 8-10 K, an integrated intensity ratio of 13CO to C18O of 3-6 and the column density (1-6)x10²²/cm2. About 57.5 per cent of the IRDC cores are gravitationally bound, which are more compact, warmer and denser. In addition, we study the mass distribution functions of the whole IRDC cores as well as the gravitationally bound cores, finding that they almost have the same power-law indices. This indicates that the evolution of the IRDC cores almost has no effect on the mass spectrum of the molecular cores and thus can be used to study the stellar initial mass function. Moreover, three IRDC cores G24.00-3, G31.38-1 and G34.43-4 are detected to have large-scaled infall motions. Two different outflows are further found for the IRDC core G34.43-4 and one of them is in high collimation.