Connection among environment, cloud-cloud collision speed, and star formation activity in the strongly barred galaxy NGC1300

TL;DR

This study investigates cloud-cloud collision speeds in the barred galaxy NGC1300, revealing regional differences and suggesting that factors like molecular gas density influence star formation activity beyond collision speed alone.

Contribution

It provides the first detailed measurement of CCC speeds in different regions of NGC1300 and links these to star formation activity, highlighting additional factors affecting star formation suppression.

Findings

CCC speeds are higher in the bar and bar-end than in the arm.

High-speed CCCs are present in both star-forming and non-star-forming regions.

Differences in molecular gas density may explain variations in star formation activity.

Abstract

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.