Large velocity dispersion of molecular gas in bars of strongly barred galaxies, NGC 1300 and NGC 5383

TL;DR

This study observes molecular gas in the bars of NGC 1300 and NGC 5383, finding higher velocity dispersions in bars supporting a new model where cloud collisions suppress star formation.

Contribution

It provides observational evidence for a new scenario where increased cloud collision velocities in bars inhibit star formation, based on CO line width measurements.

Findings

Higher velocity dispersions in bar regions compared to arms

Molecular gas present in bars without associated HII regions

Supports the cloud collision suppression model

Abstract

We carried out $^{12}$CO(J = 1 -0) observations toward bar and arm regions of strongly barred galaxies, NGC 1300 and NGC 5383, with the Nobeyama 45-m radio telescope (beamsize of 1-2 kpc in the galaxies). The aim of the observations is to qualitatively examine a new scenario for the suppression of star formation in bars based on recent high-resolution numerical simulations: higher speed collisions between molecular clouds in the bar region compared with the arm region suppress the massive star formation. CO emissions were detected from all the regions, indicating the presence of the molecular gases in the strong bars without associating clear HII regions. In both galaxies, the velocity width of the CO line profile tends to be larger in the bar region than in the arm region, which is qualitatively consistent with the new scenario.