# Collective non-thermal emission from an extragalactic jet interacting with stars

## TL;DR

This paper models the non-thermal high-energy emission resulting from interactions between extragalactic jets and stellar winds, highlighting potential contributions to observed gamma-ray fluxes in active galactic nuclei.

## Contribution

It introduces a detailed calculation of particle acceleration and emission in jet-wind shocks across different galaxy types, expanding understanding of jet-related high-energy phenomena.

## Key findings

- A significant fraction (0.1-10%) of jet energy can be used for particle acceleration.
- Non-thermal emission from jet-wind interactions can dominate high-energy radiation on jet scales.
- In the case of M87, this mechanism is insufficient to explain observed gamma-ray fluxes.

## Abstract

The central regions of galaxies are complex environments, rich in evolved and/or massive stars. For galaxies hosting an active galactic nucleus (AGN) with jets, the interaction of the jets with the winds of the stars within can lead to particle acceleration, and to extended high-energy emitting regions. We compute the non-thermal emission produced by the jet flow shocked by stellar winds on the jet scale, far from the jet-star direct interaction region. First, prescriptions for the winds of the relevant stellar populations in different types of galaxies are obtained. The scenarios adopted include galaxies with their central regions dominated by old or young stellar populations, and with jets of different power. Then, we estimate the available energy to accelerate particles in the jet shock, and compute the transport and energy evolution of the accelerated electrons, plus their synchrotron and inverse Compton emission, in the shocked flow along the jet. A significant fraction of the jet energy, $\sim 0.1-10$\%, can potentially be available for the particles accelerated in jet-wind shocks in the studied cases. The non-thermal particles can produce most of the high-energy radiation on jet scales, far from the jet shock region. This high-energy emission will be strongly enhanced in jets aligned with the line of sight due to Doppler boosting effects. The interaction of relativistic jets with stellar winds may contribute significantly to the persistent high-energy emission in some AGNs with jets. However, in the particular case of M87, this component seems too low to explain the observed gamma-ray fluxes.