Star Cluster Formation in an ALMA View

Wednesday, 24 July 2019 9 a.m. — 10 a.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
YU CHENG (University of Virginia and Gemini South Visiting Astronomer)

Star clusters are the building blocks of galaxies. Several fundamental questions about cluster formation are still being debated, including “what is the timescale” and “what sets the star formation efficiency”? G286.21+0.17 is a massive protocluster at a distance of 2.5 kpc. We have mapped a field of 5.3’×5.3’ towards G286 with the Atacama Large Millimeter/submillimeter Array(ALMA) in band 6(1.3mm) at a spatial resolution of 1.0’’ (2500AU). The dense core mass function (CMF) is measured using millimeter continuum emission. For masses M ≳ 1 M⊙, our fiducial dendrogram-identified CMF can be fit with a power law with index α ≃ 1.24 ± 0.17, consistent with the Salpeter stellar IMF. The spectral line observations, including species of C18O, N2D+, DCO+ and DCN have allowed us to study the gas kinematics/dynamics at different spatial scales, from a few pc clouds to 2500AU dense cores. We have also obtained ALMA long baseline data (1.3mm) for this region with an unprecedented angular resolution of 20 mas (50AU) and a sensitivity of 20 uJy (corresponding to 1 Jupiter mass), which reveals hierarchical fragmentation of dense cores and a cluster of distributed protostellar disks. We discuss the implications of these results for star and star cluster formation theories.