2017MNRAS.470.3332I

The first direct detections of gravitational waves (GWs) from black hole (BH) mergers, GW 150914, GW 151226 and LVT 151012, give a robust lower limit ∼70 000^+170 000_–61 000 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 ∼10^37 ± 3^ erg s^–1 as PeVatrons, positron factories and/or unidentified TeV gamma-ray sources. Additional ∼300 BH jet nebulae could be detectable by 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.