Unveiling massive stellar clusters as cosmic ray accelerators

The origin of Galactic cosmic rays is a persistent and fundamental open question in modern astrophysics.

Gamma-ray observations have in the past five years suggested young massive stellar clusters as prominent cosmic ray accelerators but remain unable to provide smoking gun evidence for this scenario.

Specifically, the exact sites, acceleration physics, and power sources of cosmic ray production in such clusters are unknown and unquantified.

Building on revolutionary developments in radio telescope capabilities to overcome these limitations, I will explore novel MeerKAT and Australian Square Kilometre Array Precursor observations to, for the first time: (i) directly locate the shock sites of cosmic ray acceleration in three massive clusters; (ii) measure the microphysical properties of the acceleration process using stellar bow shocks as pristine, isolated testbeds; and (iii) obtain the most complete measurements of the power reservoir in massive star winds in these clusters.

This three-step approach will confirm young massive stellar clusters as cosmic ray accelerators, reveal the exact acceleration scenario for the first time, measure currently unconstrained but essential physical properties for cluster modelling (large scale and local magnetic fields, acceleration efficiencies, cumulative stellar wind power), and lay the foundation for synergies between planned future radio and gamma-ray telescopes.

I will openly distribute all analysed radio images and analysis tools developed in this Action to facilitate open science and maximize their impact as a training tool for the astrophysical community. I will furthermore develop an interactive high-school engagement module based on the analysed MeerKAT data.

Performing this work at the UvA, I will simultaneously acquire the research, management, and supervision training that will complete my transition into a fully rounded research group leader.