The amount of mass contained in low-mass objects is investigated anew. Instead of using a mass–luminosity relation to convert a luminosity function to a mass function, I predict the mass-luminosity relation from assumed mass functions and the luminosity functions of Jahreiss &Wielen (1997) and Gould, Bahcall & Flynn (1997). Comparison of the resulting mass–luminosity relations with data for bin...

Based on recent X-ray observations of the Milky Way, Magellanic Clouds and nearby starburst galaxies we study population of high mass X-ray binaries, their connection with ultra-luminous X-ray sources and relation to the star formation. Although more subtle SFR dependent effects are likely to exist, the data in the lg(LX) ∼ 36 − 40.5 luminosity range are broadly consistent with existence of a "...

We provide a simple theoretical model for the quasar luminosity function at high redshifts that naturally reproduces the statistical properties of the luminous SDSS quasar sample at redshifts z ∼ 4.3 and z & 5.7. Our model is based on the assumptions that quasar emission is triggered by galaxy mergers, and that the black hole mass is proportional to a power-law in the circular velocity of the h...