Physical Properties of Molecular Clouds in the Overlap Region of the Merging Antennae Galaxies

As the closest major galaxy merger and home to thousands of super starclusters (SSCs), the Antennae Galaxies (NGC 4038 and NGC 4039) are an importantlocation to study the molecular clouds at sites of vigorous star formation. Wecataloged giant molecular clouds (GMCs) in the region where the two galaxiesoverlap using high-resolution (~0.1" ~10 pc) Atacama LargeMillimeter/submillimeter Array (ALMA) observations of the 12CO(2-1) and13CO(2-1)} emission lines. Of the 72 individual GMCs identified in the overlapregion, 17 are within uncertainties of having the necessary mass, pressure, andsize needed to form super star clusters (SSCs). Of those 17 GMCs, only one hassignificant ionizing radiation, indicating that the birth environments arelikely still intact in the 16 other GMCs. We compared the physical propertiescalculated from 12CO(2-1) GMC data with observations of 10 other galaxiesobtained using the same emission line and similar resolution. Compared to othersources in this sample, the GMCs from the Antennae, as well as in otherstarbursts and in the centers of galaxies, have the highest luminosities,surface densities, and turbulent pressures. The GMCs in starbursts and at thecenters of galaxies also have large linewidths, although the linewidths in theAntennae are among the widest. These comparative results also indicate that theAntennae GMCs have the highest virial parameters despite their high densities.