Kavli Affiliate: Debora Sijacki

| First 5 Authors: Francisco Rodríguez Montero, Sergio Martin-Alvarez, Adrianne Slyz, Julien Devriendt, Yohan Dubois

| Summary:

During the last decade, cosmological simulations have managed to reproduce
realistic and morphologically diverse galaxies, spanning the Hubble sequence.
Central to this success was a phenomenological calibration of the few included
feedback processes, whilst glossing over higher complexity baryonic physics.
This approach diminishes the predictive power of such simulations, preventing
to further our understanding of galaxy formation. To tackle this fundamental
issue, we investigate the impact of cosmic rays (CRs) and magnetic fields on
the interstellar medium (ISM) and the launching of outflows in a cosmological
zoom-in simulation of a Milky Way-like galaxy. We find that including CRs
decreases the stellar mass of the galaxy by a factor of 10 at high redshift and
$sim 4$ at cosmic noon, leading to a stellar mass to halo mass ratio in good
agreement with abundance matching models. Such decrease is caused by two
effects: i) a reduction of cold, high-density, star-forming gas, and ii) a
larger fraction of SN events exploding at lower densities, where they have a
higher impact. SN-injected CRs produce enhanced, multi-phase galactic outflows,
which are accelerated by CR pressure gradients in the circumgalactic medium of
the galaxy. While the mass budget of these outflows is dominated by the warm
ionised gas, warm neutral and cold gas phases contribute significantly at high
redshifts. Importantly, our work shows that future JWST observations of
galaxies and their multi-phase outflows across cosmic time have the ability to
constrain the role of CRs in regulating star formation.

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