Embedded Young Massive Star Clusters in the Antennae Merger
ASTROPHYSICAL JOURNAL(2022)
Abstract
The properties of young massive clusters (YMCs) are key to understanding the star formation mechanism in starburst systems, especially mergers. We present Atacama Large Millimeter/submillimeter Array high-resolution (similar to 10 pc) continuum (100 and 345 GHz) data of YMCs in the overlap region of the Antennae galaxy. We identify six sources in the overlap region, including two sources that lie in the same giant molecular cloud (GMC). These YMCs correspond well with radio sources in lower-resolution continuum (100 and 220 GHz) images at GMC scales (similar to 60 pc). We find most of these YMCs are bound clusters through virial analysis. We estimate their ages to be similar to 1 Myr and that they are either embedded or just beginning to emerge from their parent cloud. We also compare each radio source with a Pa beta source, and find they have consistent total ionizing photon numbers, which indicates they are tracing the same physical source. By comparing the free-free emission at similar to 10 pc scale and similar to 60 pc scale, we find that similar to 50% of the free-free emission in GMCs actually comes from these YMCs. This indicates that roughly half of the stars in massive GMCs are formed in bound clusters. We further explore the mass correlation between YMCs and GMCs in the Antennae and find it generally agrees with the predictions of the star cluster simulations. The most massive YMC has a stellar mass that is 1%-5% of its host GMC mass.
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Key words
young massive star clusters,antennae merger,embedded
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