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The Morpho-Kinematic Architecture of Super Star Clusters in the Center of NGC253

Presentation #130.07 in the session Star Associations.

Published onJun 29, 2022
The Morpho-Kinematic Architecture of Super Star Clusters in the Center of NGC253

The bar-fed starburst in the center of the nearby galaxy NGC253 hosts a population of more than a dozen super star clusters (SSCs) revealed by submillimeter observations from ALMA and the VLA. These SSCs are massive (M*≳105 M), compact (R~1 pc), and gas-rich (Mgas/M*~1). At least three of the SSCs show spectral evidence of massive molecular gas outflows, thought to be powered by dust-reprocessed radiation pressure, O star stellar winds, or a combination of both mechanisms. In projection, the SSCs appear as a thin, almost linear, structure about 170 pc in length, reminiscent of the Central Molecular Zone (CMZ) of the Milky Way. The individual SSCs are connected by more diffuse dust and molecular gas emission. However, precisely how gas is flowing from the larger scale bar (~2 kpc) down to the nuclear region (~200 pc) to power the nuclear starburst and result in the formation of these SSCs is not well measured. In this work, we use the SSCs themselves as the tracers of the gas flows. We use ALMA observations of the dust continuum and molecular gas emission with a spatial resolution of 47 milliarcseconds (0.8 pc) to morpho-kinematically determine the arrangement of the SSCs in the context of the larger scale bar flows and orbits. From the ALMA spectra, we have precise measurements of the systemic velocities of each of the SSCs. By applying models developed for the CMZ to these observations, we find that the arrangement of the SSCs in NGC253 is consistent with an edge-on ring or crossing streams connected to the larger scale bar, both in terms of the morphology and the kinematics. From these constraints, we can make predictions for model-dependent cluster age gradients, which we will be able to test with our approved Cycle 1 JWST program.

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