Oral Presentation

A distance ladder of cosmic ray feedback signatures in star-forming galaxies: the high-redshift domain

Author(s): Ellis R. Owen (Osaka University)

Presenter: Ellis Owen (Osaka University)

High-redshift primordial galaxies have recently been found with evolved stellar populations and complex star-formation histories reaching back to 250 Myr after the Big Bang. Their intense bursts of star-formation appear to be interspersed with sustained periods of strong quenching, however the processes underlying this evolutionary behaviour remain unclear. Unlike later epochs, galaxies in the early Universe are not located in large associations like clusters. Instead, they co-evolve with their developing circumgalactic halo as relatively isolated ecosystems, presumably fed by inflows of pristine gas from the cosmic web. The mechanisms that could bring about the downfall of their star-formation are primarily intrinsic, and feedback processes associated with their intense starburst episodes likely play an important role. Cosmic rays are a viable agent to deliver this feedback, and could account for the star-formation histories inferred for these systems. The cosmic ray impact on galaxies may be investigated using the wealth of multi-wavelength data soon to be obtained with the armada of new generation and upcoming facilities, including ALMA, JWST, SKA and CTA. Observational means to probe their action across the electromagnetic spectrum can be arranged into a distance ladder of cosmic ray feedback signatures. With a clear understanding of how cosmic ray activity in primordial systems can be traced, it will be possible to extend this ladder to high-redshifts and map-out the role played by cosmic rays in shaping galaxy evolution over cosmic time. In this talk, I will focus on the observational signatures of cosmic ray feedback in high-redshift galaxies, and up-coming opportunities with JWST, ALMA and other instruments.