The birth of a super-star cluster: NGC 5253

We present images of the 7 mm free-free emission from the radio "supernebula" in NGC 5253 made with the Very Large Array and the Pie Town link. The images reveal structure in the nebula, which has a ≤1 pc (∼50 mas radius) core requiring the excitation of 1200 O7 stars. The nebula is elongated, with an arc of emission curving to the northeast and to the south. The total ionizing flux within the central 1.″2 (∼20 pc) is 7 × 10⁵² s^-1, corresponding to 7000 O7 stars. We propose that the radio source is coincident with a small very red near-IR cluster and apparently linked to a larger optical source some 10 pc away on the sky. We speculate on the causes of this structure and what it might tell us about the birth of the embedded young super-star cluster.