Physical properties, kinetics and mass function of 12 northern infrared dark clouds

TL;DR

This study systematically analyzes the physical, chemical, and kinetic properties of 12 northern infrared dark clouds using molecular line and continuum observations, revealing their structure, core properties, and mass functions relevant to star formation.

Contribution

It provides the first comprehensive analysis of IRDCs' properties, core mass distribution, and infall/outflow motions, linking IRDC characteristics to star formation processes.

Findings

41 IRDC cores identified with typical temperatures of 8-10 K

57.5% of cores are gravitationally bound, denser and warmer

Mass functions follow similar power-law indexes, unaffected by evolution

Abstract

The physical, chemical and kinetic characteristics of 12 northern infrared dark clouds (IRDCs) are systematic studied using the $\rm ^{13}CO $ (1-0) and $\rm C^{18}O$ (1-0) lines, observed with the PMO 13.7 m radio telescope, the 1.1 mm Bolocam Galactic Plane Survey (BGPS) data and GLIMPSE Spitzer IRAC $\rm 8 \,\mu m$ 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 $8\sim10$ K, a integrated intensity ratio of $\rm ^{13}CO$ to $\rm C^{18}O$ $3\sim6$ and the column density $(1\sim6)\times 10^{22}\, \rm cm^{-2}$. About $57.5\%$ 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 gravitational bound cores, finding that they almost have the same power-law indexes. This indicates that the evolution of the IRDC cores almost have 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 IRDC core G34.43-4 and one of them is in high collimation.