Connection among environment, cloud-cloud collision speed, and star
  formation activity in the strongly barred galaxy NGC1300
  Cloud-cloud collision (CCC) has been suggested as a mechanism to induce
massive star formation. Recent simulations suggest that a CCC speed is
different among galactic-scale environments, which is responsible for observed
differences in star formation activity. In particular, a high-speed CCC is
proposed as a cause of star formation suppression in the bar regions in barred
spiral galaxies. Focusing on the strongly barred galaxy NGC1300, we investigate
the CCC speed. We find the CCC speed in the bar and bar-end tend to be higher
than that in the arm. The estimated CCC speed is $\sim20~\rm km~s^{-1}$,
$\sim16~\rm km~s^{-1}$, and $\sim11~\rm km~s^{-1}$ in the bar, bar-end, and
arm, respectively. Although the star formation activity is different in the bar
and bar-end, the CCC speed and the number density of high-speed CCC with $>
20~\rm km~s^{-1}$ are high in both regions, implying the existence of other
parameters that control the star formation. The difference in molecular gas
mass (average density) of the giant molecular clouds (GMCs) between the bar
(lower mass and lower density) and bar-end (higher mass and higher density) may
be cause for the different star formation activity. Combining with our previous
study (Maeda et al.), the leading candidates of causes for the star formation
suppression in the bar in NGC1300 are the presence of a large amount of diffuse
molecular gases and high-speed CCCs between low mass GMCs.
