5 Conclusion

We have argued that Galactic microquasars produce cosmic rays with energies of a few GeV/nucleon. Under preferable conditions (i.e., if particles in the jet are cold and do not suffer significant adiabatic losses before escaping the acceleration region) this component should be detectable as a narrow peak with energy $\sim$ $\Gamma_{\rm jet}~m_{\rm p}~c^2/{\rm nucleon}$ in the Galactic CR spectrum. The superposition of several such peaks would then reflect the distribution of Lorentz factors of Galactic jet sources.

In addition, diffusive acceleration of particles might produce a powerlaw distribution of particles with a low energy turnover at energies around $\Gamma_{\rm jet}^2 m_{\rm p} c^2$ to $\Gamma_{\rm jet}^3 m_{\rm p} c^2$, visible as an edge-like feature in the CR spectrum.

The locally measured contribution to the CR spectrum will be strongly dominated by sources operating close by (within a distance of about one Galactic disk height and within the past $10^7~{\rm yrs}$), since at distances much larger than that the contribution from a given microquasar falls off exponentially. We estimate the global energy content in the CR component accelerated in Galactic relativistic jets to be at the 0.1% to 10% level of the total Galactic CR luminosity.

This CR contribution from Galactic relativistic jet sources might be strongly overabundant in heavy elements, reflecting the composition of the accretion disk where the jets are launched. Thus, it is possible that the chemical abundance measured in the GeV region (where we expect the contribution from jets to show the strongest effect) will differ slightly from the chemical composition at higher energies.

While signatures of the CR component from microquasars might already be buried in existing data, the upcoming solar minimum and the launch of AMS 02 will offer ideal conditions to search for this component and to put constraints on the microquasar activity in the nearby universe.

We suggested that the absence of any observable traces of microquasar component in the cosmic ray proton spectrum could be used to argue in favor of electron-positron jets. For this case, we showed that existing OSSE/GRO observations of the Galactic electron-positron annihilation rate can be used to limit the power in cold electron-positron jets inside the Galaxy to $L_{\pm} < 3\times 10^{38}~{\rm ergs~s^{-1}}$.

Acknowledgements

We would like to thank Roger Blandford, Andrei Bykov, Richard Mewaldt, Igor Moskalenko, and Vladimir Ptuskin for insightful discussions and comments on the manuscript. We would also like to thank Andrew Strong for providing access to the GALPROP code. We would like to thank the referee Rob Fender for helpful comments regarding all aspects of the paper. Rashid Sunyaev, as a Gordon Moore Scholar, thanks Caltech for its hospitality during the work on this paper. This research has made use of the public GBI monitoring database hosted by NRAO.