Hunting star forming galaxies in the gamma-ray domain

¹ Laboratoire Univers et THeories (LUTH), Observatoire de Paris-Meudon, F-92195 Meudon Cedex, France
² Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
³ Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France
⁴ Institut Universitaire de France (IUF), 1 rue Descartes, 75231 Paris Cedex 05, France

^⋆ Corresponding author: pkornecki@iaa.csic.es

Received: 26 November 2024
Accepted: 26 April 2025

Abstract

Context. Star-forming galaxies emit γ rays with relatively low luminosity, but the study of their emission is no less captivating. While it is known that their γ-ray luminosity in the GeV band is strongly linked to their star formation, the origin of their emission at higher energies remains uncertain due to limited observations.

Aims. Our aim is to assemble the largest possible sample of star-forming galaxies with potential detectability by the new generation of Cherenkov telescopes.

Methods. To achieve this, we compile a comprehensive sample of galaxies, including those previously detected by Fermi-LAT in the GeV energy range, as well as a larger sample of star-forming galaxies in the Local Volume that have been cataloged in the near-infrared band. We estimate their γ-ray flux by assuming a proportional relationship with their star formation rate, and then select the brightest candidates. The predicted spectra in the TeV band are derived using a simple empirical model normalized to the star formation rate and a model based on extrapolating the latest Fermi-LAT data to higher energies. The ground-based detectability of γ-ray emission from these sources is assessed through a comparison with the most recent instrument response functions.

Results. Our investigation reveals that almost a dozen star-forming galaxies may be detectable by upcoming γ-ray telescopes.

Conclusions. The observation of numerous star-forming galaxies in the TeV band is a fundamental piece of the panchromatic puzzle for understanding the physics inside these galaxies. The significant increase in the number of galaxies that will be able to be studied in detail in the near future, particularly with the Cherenkov Telescope Array Observatory, promises a major step forward in the study of the conditions of acceleration and transport of cosmic rays in nearby extragalactic environments.