Kavli Affiliate: Martin Haehnelt
| First 5 Authors: Marion Farcy, Joakim Rosdahl, Yohan Dubois, Jérémy Blaizot, Sergio Martin-Alvarez
| Summary:
Galaxies form and evolve via a multitude of complex physics. In this work, we
investigate the role of cosmic ray (CR) feedback in galaxy evolution and
reionisation, by examining its impact on the escape of ionising radiation from
galaxies. For this purpose, we present two Sphinx cosmological
radiation-magneto-hydrodynamics simulations, allowing for the first time a
study of the impact of CR feedback on thousands of resolved galaxies during the
Epoch of Reionisation (EoR). The simulations differ in their feedback
prescriptions: one adopts a calibrated strong supernova (SN) feedback, while
the other simulation reduces the strength of SN feedback and includes CR
feedback instead. We show that both comparably regulate star formation,
reasonably match observations of high-redshift UV luminosity functions, and
produce a similar amount of hydrogen ionising photons. In contrast to the model
with strong SN feedback, the model with CRs lead to incomplete reionisation,
which is in strong disagreement with observational estimates of the
reionisation history. This is due to CR feedback shaping the ISM differently,
filling with gas the low density cavities otherwise carved by SN explosions. As
a result, this reduces the escape of ionising photons, at any halo mass, and
primarily in the close vicinity of the stars. Our study indicates that CR
feedback regulates galaxy growth during the EoR, but negatively affects
reionisation, a tension which paves the way for further exploration and
refinement of existing galaxy formation and feedback models. Such improvements
are crucial in order to capture and understand the process of reionisation and
the underlying evolution of galaxies through cosmic time.
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