Population X:: Are the super-Eddington X-ray sources beamed jets in microblazars or intermediate mass black holes?

Recent X-ray observations reveal an increasing number of X-ray sources in nearby galaxies exceeding luminosities of L-x greater than or similar to 2 x 10(39) erg s(-1). Assuming isotropic emission, the Eddington limit suggests a population of intermediate-mass black holes of M-. >> 10 M.. However, Markoff et al. (2001a) proposed that jets may be contributing to the X-ray emission from X-ray binaries (XRBs), implying that some X-ray sources may be relativistically beamed. This could reduce the required black hole masses to standard values. To test this hypothesis, we investigate a simple X-ray population synthesis model for X-ray point sources in galaxies with relativistic beaming and compare it with an isotropic emission model. The model is used to explain a combined data set of X-ray point sources in nearby galaxies. We show that the current distributions are consistent with black hole masses M. less than or similar to 10 and bulk Lorentz factors for jets in microquasars of gamma(j) similar to 5. Alternatively, intermediate mass black holes up to 1000 M. are required which are distributed in a powerlaw with roughly dN/dM similar to M-2.