The impact of a massive star cluster on its surrounding matter in the Antennae overlap region

Abstract

Super star clusters (SSCs), likely the progenitors of globular clusters, are one of the most extreme forms of star formation. Understanding how SSCs form is an observational challenge. Theoretical studies establish that, to form such clusters, the dynamical timescale of their parent clouds has to be shorter than the timescale of the disruption of their parent clouds by stellar feedback. However, due to insufficient observational support, it is still unclear how feedback from SSCs acts on the matter surrounding them. Studying feedback in SSCs is essential to understanding how such clusters form. Based on ALMA and VLT observations, we study this process in a SSC in the overlap region of the Antennae galaxies (22 Mpc), a spectacular example of a burst of star formation triggered by the encounter of two galaxies. We analyze a unique massive (~107M·) and young (1-3.5 Myr) SSC, still associated with compact molecular and ionized gas emission, which suggest that it may still be embedded in its parent molecular cloud. The cluster has two CO velocity components, a low-velocity one spatially associated with the cluster, and a high-velocity one distributed in a bubble-like shape around the cluster. Our results on the low-velocity component suggest that this gas did not participate in the formation of the SSC. We propose that most of the parent cloud has already been blown away, accelerated at the early stages of the SSC evolution by radiation pressure, in a timescale ~1 Myr. The high-velocity component may trace outflowing molecular gas from the parent cloud. Supporting evidence is found in shock-heated H2 gas and escaping Brγ gas associated with this component. The low-velocity component may be gas that was near the SSC when it formed but not part of its parent cloud or clumps that migrated from the SGMC environment. This gas would be dispersed by stellar winds and supernova explosions. The existing data is inconclusive as to whether or not the cluster is bound and will evolve as a globular cluster. Within ~100 pc of the cluster, we estimate a lower limit for the SFE of 17%, smaller than the theoretical limit of 30% needed to form a bound cluster. Further higher spatial resolution observations are needed to test and quantify our proposed scenario.