Invited Presentation

Constraining the structure and dynamics of black hole jets

Author(s): William Potter (University of Oxford) Garret Cotter (University of Oxford)

Presenter: William Potter (University of Oxford)

Black hole jets emit radiation across the entire electromagnetic spectrum and this is one of the most important windows into understanding the physical processes occurring along jets. I will present a new fluid jet emission model consisting of an accelerating, magnetically dominated parabolic base transitioning to a slowly decelerating conical section motivated by observations, simulations and theory. We set the inner geometry of our multi-zone jet using radio observations of the jet in M87 which transitions from parabolic to conical at 10^5 Schwarzschild radii. Our model is able to reproduce the observed spectra of a large sample of blazars with unprecedented precision across all wavelengths, from radio to gamma-rays, for the first time. Using this model we are able to constrain the radius and location at which the synchrotron emission is brightest in these jets by fitting the optically thick to thin synchrotron break at radio wavelengths. We find that the radius of the jet at which the synchrotron emission is brightest (where the jet first approaches equipartition) scales approximately linearly with the jet power and the maximum bulk Lorentz factor of the jet also increases with jet power. We find evidence for a bimodal accretion rate in blazars with BL Lacs corresponding to low power FRI type jets and FSRQs corresponding to high power FRII type jets. These new results allow us to understand and constrain the structure and dynamics of jets by fitting to their multiwavelength spectra and lead us to a deeper understanding of the physics behind the blazar sequence.