Exploring the capability of the HH 80-81 protostellar jet to accelerate relativistic particles

¹ Instituto de Astrofísica de Andalucía (IAA), CSIC, 18008 Granada, Spain
² Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, 15738 Zeuthen, Germany

^⋆ Corresponding author; jmendez@iaa.es

Received: 3 October 2024
Accepted: 24 January 2025

Abstract

Context. Protostellar jets driven by massive protostars are collimated outflows producing high-speed shocks through dense interstellar medium. Fast shocks can accelerate particles up to relativistic energies via diffusive shock acceleration, producing non-thermal emission that can generate γ-ray photons. HH 80-81 is one of the most powerful collimated protostellar jets in our Galaxy, with non-thermal emission detected in radio, X-ray, and γ-ray bands. Characterizing the γ-ray emission that originates in the accelerated particles of the region is crucial for demonstrating the capability of protostars to accelerate cosmic rays.

Aims. Our goal is to determine the particle distribution that is producing the γ-ray spectrum of HH 80-81 in order to ascertain the leptonic or hadronic origin of the γ-ray emission. We aim to associate the high-energy emission in the region with the HH 80-81 system, characterize its spectrum, and elaborate emission models based on what we expect from the diffusive shock acceleration.

Methods. We use the 15 yr database provided by the Fermi-LAT satellite to study the high-energy emission of the jet, spanning from 300 MeV to 100 GeV. In addition, we perform a source association based on positional arguments. Then, we employ the naima and Gamera softwares to analyze the possible mechanisms that are producing γ-rays, considering the ambient conditions. We perform a radiative fitting and study the nature of the particles behind the γ-ray emission.

Results. By analyzing all the candidates to produce the γ-ray emission that we detect, we conclude that HH 80-81 is the most probable candidate to explain the γ-ray emission in the region. The detected spectrum can be explained by both hadronic and leptonic particle components.