Outflows from Super Star Clusters in the Central Starburst of NGC253
  Young massive clusters play an important role in the evolution of their host
galaxies, and feedback from the high-mass stars in these clusters can have
profound effects on the surrounding interstellar medium. The nuclear starburst
in the nearby galaxy NGC253 at a distance of 3.5 Mpc is a key laboratory in
which to study star formation in an extreme environment. Previous high
resolution (1.9 pc) dust continuum observations from ALMA discovered 14
compact, massive super star clusters (SSCs) still in formation. We present here
ALMA data at 350 GHz with 28 milliarcsecond (0.5 pc) resolution. We detect
blueshifted absorption and redshifted emission (P-Cygni profiles) towards three
of these SSCs in multiple lines, including CS 7$-$6 and H$^{13}$CN 4$-$3, which
represents direct evidence for previously unobserved outflows. The mass
contained in these outflows is a significant fraction of the cluster gas
masses, which suggests we are witnessing a short but important phase. Further
evidence of this is the finding of a molecular shell around the only SSC
visible at near-IR wavelengths. We model the P-Cygni line profiles to constrain
the outflow geometry, finding that the outflows must be nearly spherical.
Through a comparison of the outflow properties with predictions from
simulations, we find that none of the available mechanisms completely explains
the observations, although dust-reprocessed radiation pressure and O star
stellar winds are the most likely candidates. The observed outflows will have a
very substantial effect on the clusters' evolution and star formation
efficiency.
