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