The COSI Extragalactic Science Goals

COSI will explore the MeV emission from active galactic nuclei; most of them will be blazars. COSI will study the MeV gap in the blazar spectrum, which has long been considered as the transition from synchrotron self Compton to external Compton for flat spectrum radio quasars. Thanks to its polarimetry capabilities, COSI may detect polarization in the MeV band, which can pinpoint hadronic contributions in the blazar spectrum. COSI will also study the potentially most powerful blazars whose high-energy component peaks in the MeV band, and investigate potential extreme high synchrotron peaked blazars that have their synchrotron component peaks in the MeV band.