Abstract
We investigated the influence of the random velocity of molecular gas on star-formation activities of six nearby galaxies. The physical properties of a molecular cloud, such as temperature and density, influence star-formation activities in the cloud. Additionally, local and turbulent motions of molecules in a cloud may exert substantial pressure on gravitational collapse and thus prevent or reduce star formation in the cloud. However, the influence of gas motion on star-formation activities remains poorly understood. We used data from the Atacama Large Millimeter/submillimeter Array to obtain 12CO(J = 1 − 0) flux and velocity dispersion. We then combined these data with 3.6 and 8 micron midinfrared data from the Spitzer Space Telescope to evaluate the effects of gas motion on star-formation activities in several nearby galaxies. We discovered that relatively high velocity dispersion in molecular clouds corresponds with relatively low star-formation activity. Considering the velocity dispersion as an additional parameter, we derived a modified Kennicutt-Schmidt law with a gas surface density power index of 0.84 and velocity dispersion power index of −0.61.
Highlights
The history of the evolution of galaxies is one of the most critical points of inquiry in modern astronomy
We investigated the relation between 12CO(J = 1−0) luminosity surface density, velocity dispersion, and star-formation rate (SFR) surface density for each galaxy
We found that the 12CO(J = 1−0) luminosity surface density is highly correlated with the SFR surface density for most of the selected galaxy regions except for the bar region of NGC 3627 and the arm region of NGC 1365, the latter of which has only 11 data points. (Table 3)
Summary
The history of the evolution of galaxies is one of the most critical points of inquiry in modern astronomy. Zhang et al (2014a) present SMA observations of 14 massive molecular clumps in the 345-GHz band and conclude that magnetic fields at the core scale of 0.01–0.1 pc tend to be relatively organized; the magnetic fields of over 60% of the cores are perpendicular to the major axes of the cores. These results demonstrate that magnetic fields play a critical role in the collapse and formation of dense cores.
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