  The first direct detections of gravitational waves (GWs) from black hole (BH)
mergers, GW150914, GW151226 and LVT151012, give a robust lower limit $\sim
70000$ on the number of merged, highly-spinning BHs in our Galaxy. The total
spin energy is comparable to all the kinetic energy of supernovae that ever
happened in our Galaxy. The BHs release the spin energy to relativistic jets by
accreting matter and magnetic fields from the interstellar medium (ISM). By
considering the distributions of the ISM density, BH mass and velocity, we
calculate the luminosity function of the BH jets, and find that they can
potentially accelerate TeV-PeV cosmic-ray particles in our Galaxy with total
power $\sim 10^{37\pm 3}$ erg s$^{-1}$ as PeVatrons, positron factories and/or
unidentified TeV gamma-ray sources. Additional $\sim 300$ BH jet nebulae could
be detectable by CTA (Cherenkov Telescope Array). We also argue that the
accretion from the ISM can evaporate and blow away cold material around the BH,
which has profound implications for some scenarios to predict electromagnetic
counterparts to BH mergers.
