Toy model for the acceleration of blazar jets

Abstract

Context. Understanding the acceleration mechanism of astrophysical jets has been a cumbersome endeavor from both the theoretical and observational perspective. Although several breakthroughs have been achieved in recent years, on all sides, we are still missing a comprehensive model for the acceleration of astrophysical jets. Aims. In this work we attempt to construct a simple toy model that can account for several observational and theoretical results and allow us to probe different aspects of blazar jets usually inaccessible to observations. Methods. We used the toy model and Lorentz factor estimates from the literature to constrain the black hole spin and external pressure gradient distributions of blazars. Results. Our results show that (1) the model can reproduce the velocity, spin and external pressure gradient of the jet in M 87 inferred independently by observations; (2) blazars host highly spinning black holes with 99% of BL Lac objects and 80% of flat spectrum radio quasars having spins a > 0.6; (3) the dichotomy between BL Lac objects and flat spectrum radio quasars could be attributed to their respective accretion rates. Using the results of the proposed model, we estimated the spin and external pressure gradient for 75 blazars.