Very High Energy Gamma Rays from Ultra Fast Outflows

TL;DR

This paper models particle acceleration in ultra fast outflows from active galactic nuclei to assess their potential detectability in gamma rays and neutrinos with current and future observatories.

Contribution

It introduces a model predicting gamma-ray and neutrino signals from UFOs and evaluates their detectability with next-generation telescopes.

Findings

Several UFOs could be detectable in the VHE gamma-ray domain by CTAO.

Detectability depends on hard proton spectra, high acceleration efficiencies, and amplified magnetic fields.

Next-generation VHE observatories could observe gamma-ray signatures of AGN UFOs.

Abstract

Context. Ultra fast outflows (UFOs) from active galactic nuclei (AGN) are expected to lead to the formation of sub-relativistic strong shocks expanding in a dense circumnuclear medium, and thus have the potential for being efficient particle accelerators, and to be proficient sources of gamma rays and neutrinos. Aims. We investigate the detectability of a sample of nearby identified UFOs in gamma rays and neutrinos with current and next- generation instruments. Methods. We model the acceleration of particles at the strong shocks of UFOs, and estimate the associated gamma-ray and neutrino signal. We adopt our model to investigate the prospects for detection with current and next-generation observatories. Results. We find that several UFOs could be detectable in the very-high-energy (VHE) domain - for example, by the Cherenkov Telescope Array Observatory (CTAO)- even if they remain undetected by Fermi-LAT in the high-energy range. Detectability is favored for hard proton spectra (spectral index {\alpha} \lessim 3.9), high acceleration efficiencies, and amplified magnetic fields. Our results suggest that next-generation VHE observatories could detect the first gamma-ray signatures of AGN UFOs, providing a new probe of particle acceleration in sub-relativistic shocks