February 2-5, 2021

Oral Presentation

Cause of the low star formation efficiency in the bar of the strongly barred galaxy NGC1300

Author(s): Fumiya Maeda

Presenter: Fumiya Maeda (Kyoto Univ.)

Massive star formation in bars of barred galaxies is suppressed. However, physical mechanisms of the suppression are still unclear. Focusing on the strongly barred galaxy NGC 1300, we investigated the possibility that the presence of a large amount of diffuse molecular gas, which would not contribute to the star formation, makes the SFE low. Using the 12CO(1-0) flux obtained from ALMA and Nobeyama 45-m, we find that the SFE decreases with increasing the diffuse molecular gas fraction. This result supports the possibility. However, the SFE using the molecular gas in GMCs is still significantly suppressed in the bar regions, which suggests that there should be mechanisms that control the star formation process in the GMCs. As a candidate of the mechanism, a high-speed cloud–cloud collision (CCC) is proposed. Thus, we investigated the CCC speed in NGC 1300 using the GMC catalog. We find the CCC speed in the bar tends to be higher than that in the arm. This result suggests that the high-speed CCCs suppress the massive star formation in the bars.

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