A multiwavelength view at the heart of the superwind in NGC 253

Although NGC 253 is one of the nearest starburst galaxies, the activity in its central regions is yet to be fully understood. Here we present new opti cal data from the Hubble Space Telescope of its central region, which revea l numerous discrete sources in a ring-like structure. This is combined with data at infrared, millimetre, radio and X-ray wavelengths to examine the n ature of these discrete sources and the nucleus itself. We find that the majority of optical/IR/mm sources are young star clusters that trace out a similar to 50 pc ring that defines the inner edge of a col d gas torus. This reservoir of cold gas has probably been created by gas in flow from a larger scale bar and deposited at the inner Lindblad resonance. The family of compact radio sources lie interior to the starburst ring, an d in general do not have optical or IR counterparts. They are mostly supern ova remnants. The radio nucleus, which is probably an active galactic nucle us (AGN), lies near the centre of the ring. The X-ray emission from the nuc lear source is extended in the ROSAT HRI detector indicating that not all o f the X-ray emission can be associated with the AGN. The lack of X-ray vari ability and the flat radio spectrum of the nucleus, argue against an ultral uminous SN as the dominant energetic source at the galaxy core. The diffuse emission associated with the outflowing superwind is present in the centra l region on a size scale consistent with the idea of collimation by the gas torus.