On the maximum energy of particles accelerated in astrophysical jets

Particle acceleration and magnetic field amplification in shocks at different scales

Objective

This project aims to investigate particle acceleration and magnetic field amplification in astrophysical shocks with different velocities in plasma with different densities

Low velocity shocks

A large fraction of gamma-ray sources in the Galaxy remain unidentified, and jets from protostars are among candidates to be the hidden CR accelerators and gamma-ray emitters.

Mildly relativistic shocks

Ultra High Energy Cosmic Rays have an energy of ∼100 EeV and arrive on Earth from outside the Galaxy, but their origin remains unknown. Jets from Active Galactic Nuclei have been proposed as sources

Magnetic field strength relative to the original magnetic field (top) and thermal gas mass density relative to the upstream density (bottom) at the end of the simulation. Axis are normalized to the gyroradius of injected particles in the upstream medium.

Mildly relativistic shocks in AGN jets

Mildly-relativistic shocks are found in the backflows of jet/wind interactions. The interaction of AGN jets with stars has been studied, independently, as a mechanism for jet-mass loading and non-thermal emission. In this project we go one step further and consider simultaneously particle accelerationand mixing.

The composition of UHECRs is similar to the composition of massive stellar winds. We aim to address the maximum energy and composition of the UHECR spectrum by modeling the backflows of jet/wind interactions. We consider Centaurus A as a case study where, interestingly, there is observational evidence of stars into the jet.

Spectral energy distribution for three hotspots. Black squares indicate synchrotron data and the black dashed line represent the Fermi sensitivity for 10 years of observation (Araudo et al. 2021)

Low velocity shocks in protostellar jets

Low-velocity shocks are found in the termination region of jets from massive protostars. It has been shown that neutrals can quench particle acceleration, but in the meantime DSA produces particles energetic enough to locally ionise the upstream plasma. We develop a model calculating the acceleration of particles and magnetic field amplification in a self-consistent procedure. We aim to address if protostellar jets can accelerate TeV particles, and therefore be a potential new kind of gamma-ray sources. We consider IRAS 18162-2048 (the powering massive protostar of the Herbig-Haro objects HH80 and HH81) as a case study.

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