Do nuclear starbursts obscure the X-ray background?

We propose a model for the source of the X-ray background (XRB) in which low-luminosity active nuclei (L 10 43 erg s 1 ) are obscured (N 10 23 cm 2 ) by nuclear starbursts within the inner 100 pc. The obscuring material covers most of the sky as seen from the central source, rather than being distributed in a toroidal structure, and hardens the averaged X-ray spectrum by photoelectric absorption. The gas is turbulent with velocity dispersion few 100 km s 1 and cloud-cloud collisions lead to copious star formation. Although supernovae tend to produce outflows, most of the gas is trapped in the gravity field of the star-forming cluster itself and the central black hole. A hot (T 10 6 10 7 K) virialized phase of this gas, comprising a few per cent of the total obscuring material, feeds the central engine of 10 7 M through Bondi accretion, at a sub-Eddington rate appropriate for the luminosity of these objects. If starburst-obscured objects give rise to the residual XRB, then only 10 per cent of the accretion in active galaxies occurs close to the Eddington limit in unabsorbed objects.