Table 4: Number densities and emissivities of diffirent classes of sources.
Class Space density above given luminosity Total emissivity (1027 erg s-1  $M_\odot^{-1}$)
  ( $M_\odot^{-1}$) 0.1-2.4 keV 2-10 keV 3-20 keV
ABs $\sim$ $1.2\times 10^{-2}$ ( $L_{\rm x}>10^{27.5}$ erg s-1) $(14\pm 4)$ $2.0\pm 0.8$ $2.9\pm 1.3$
CVs $(1.2\pm 0.3)\times 10^{-5}$ ( $L_{\rm x}>10^{31}$ erg s-1) $\la$ a few $1.1\pm 0.3$ $2.4\pm 0.6$
ABs+CVs   $\sim$15 $3.1\pm 0.8$ $5.3\pm 1.5$
YSs   $24\pm 3$ $1.5\pm 0.4$ $1.0\pm 0.2$
ABs+CVs+YSs   $\sim$40 $4.5\pm 0.9$ $6.2\pm 1.5$
LMXBs $\sim$ $3\times 10^{-9}$ ( $L_{\rm x}>10^{36}$ erg s-1) $\sim$40a $\sim$90b  
a Emissivity in the 0.5-2 keV band extrapolated from 2-10 keV assuming a power-law spectrum of photon index $\Gamma=1.56$, as typical of LMXBs with 1036 erg s $^{-1}<L_{\rm x}<10^{39}$ erg s-1 (Irwin et al. 2003).
b The quoted 2-10 keV emissivity for LMXBs represents an average over nearby galaxies (Gilfanov 2004).

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