Lunch talk on May. 25th, 2018

WISDOM Project – Giant Molecular Clouds in the boxy lenticular NGC4429

Speaker: 柳莉杰（牛津大学）/ Lijie Liu (University of Oxford)

Venue: Gewu 4410

Time: 12:30 PM, Friday, 25th May, 2018

Abstract: We present results on the properties of giant molecular clouds (GMCs) in the central parts of galaxies across the Hubble sequence. These were derived from high angular resolution CO observations with ALMA as part of the WISDOM project. We focus here on one early-type disk galaxies with large bulges NGC4429 as an example of our study, with data at a spatial resolution of 0.15” (or 20 pc) and a spectral resolution of 2 km/s, sufficient to accurately measure the sizes and velocity dispersions of most GMCs in the galaxy. The observed GMCs share basic properties with those of the Milky Way, with similar mass and size ranges, but there are also significant differences, suggesting that GMC properties are not universal. In particular, there seems to be genuine variations in the average mass surface density of the GMC populations, the cloud mass distributions vary across different galaxy environments, and the size-line width relations deviate strongly from that in the Milky Way, in a manner that may be caused by strong shear. We find the clouds in NGC4429 experience strong tidal tearing due to the shear in the plane of the galaxy. The influence of the external gravity on the total gravitational budget of the clouds is significant (up to 80% - 100%). Overall, due to the effect of external gravity, the cloud in NGC4429 are no longer Virialised, by only marginally self-gravitating.

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