The TeV emission of 3C273: inverse Compton radiation from shear-accelerated high-energy electrons in the large-scale jet?

TL;DR

This paper proposes that very-high-energy gamma-ray emission from 3C273's large-scale jet is produced by inverse Compton scattering of ultra-high energy electrons accelerated via shear mechanisms, explaining recent VERITAS observations.

Contribution

It introduces a shear acceleration model for high-energy electrons in large-scale jets, accounting for VHE gamma-ray emission and X-ray knots in 3C273, a novel explanation for these phenomena.

Findings

VHE gamma-ray emission can originate from kpc-scale jet regions.

Shear acceleration can produce electrons with Lorentz factors around 10^8.

The model explains the variability timescale of approximately 3 years.

Abstract

The VERITAS Collaboration recently reported the detection of very-high-energy (VHE) gamma-ray emission from the prototypical radio quasar 3C273. The temporal and the spectral properties of this component do not appear compatible with the extrapolation of the beamed blazar-like emission of the inner, pc-scale jet. We explore the possibility that the VHE component is produced in the jet at kpc scale through the inverse Compton emission of a population of ultra-high energy electrons (with Lorentz factor $\gamma\sim 10^8$). In the model these electrons are accelerated through the shear acceleration mechanism, and they also account for the still puzzling X-ray emission of knots detected by {\it Chandra} in the large-scale jets of several powerful quasars (including 3C273). In our scenario the VHE component can be interpreted as the integrated emission from the two brightest knots of the 3C273 jet. We speculate that the decay of the emission on the timescale of $\sim 3$ years could be accounted for by the scenario if the VHE radiation is produced in some compact regions in the downstream flow of a recollimation shock.