Cloud-Cloud Collisions Induce Filament-Mediated Super Star Cluster Formation in the Antennae Overlap Region: Evidence from ALMA and JWST

TL;DR

This study provides multi-wavelength observational evidence that cloud-cloud collisions in the Antennae galaxies' overlap region trigger the formation of super star clusters, highlighting a key mechanism in galaxy mergers.

Contribution

First direct observational evidence linking cloud-cloud collisions to super star cluster formation in a merging galaxy environment.

Findings

Distinct velocity components in a super giant molecular cloud suggest a collision.

Continuum emission indicates active star formation at the collision interface.

Infrared data confirms spatial coincidence with collision region.

Abstract

The formation of super star clusters (SSCs) in galaxies remains a fundamental yet unresolved problem. Among the proposed mechanisms, cloud-cloud collisions (CCCs) have been suggested as a potential trigger, although observational validation has been limited. Here we present high-resolution ($0.12^{\prime\prime}$, $\sim14\,\mathrm{pc}$) ALMA observations of CO ($J=1\!-\!0$) emission toward a super giant molecular cloud (SGMC) in the overlap region of the Antennae galaxies. The data resolve the SGMC into two distinct velocity components separated by $\sim50\,\mathrm{km\,s^{-1}}$. One component exhibits a ``U-shaped'' structure within a large filament likely shaped by ram pressure, while the other shows hub-filament morphology. Such a morphology is naturally interpreted as a CCC scenario. The 108\,GHz continuum emission detected at the apparent collision interface is dominated by free-free radiation, with an ionizing photon rate consistent with the stellar mass and age of the optically identified SSCs. Supplementary infrared imaging with JWST reveals emission spatially coincident with the inferred collision interface, further supporting the CCC scenario. These results provide compelling, multi-wavelength evidence that CCCs play a key role in triggering SSC formation in merging galaxies.