'Microquasars' and the X-ray background

The recent discovery of small active nuclei (via emission lines) in normal spiral galaxies greatly expands the range of the quasar phenomenon. By using the relationship between Lx and L(H-alpha) found in more luminous Seyfert galaxies and assuming that it holds for smaller active nuclei, a bivariate X-ray luminosity function can be calculated. This luminosity function fits naturally onto the higher luminosity X-ray luminosity function derived from the HEAO-1/A2 survey. The contribution to the X-ray background from small active nuclei hiding in large spiral galaxies is greater than 15 percent.