“Introducing SPHINX-MHD: the impact of primordial magnetic fields on the first galaxies, reionization, and the global 21-cm signal” studies the effects of primordial magnetic fields on high-redshift galaxy formation, using new SPHINX runs with radiative magneto-hydrodynamics. The simulations show that realistic-magnitude primordial fields do not have a large impact on star formation, but stronger magnetic fields tend to make galaxies somewhat more compact and have slightly stronger ionising escape fractions. Primordial field spectral indices of about -2.6 can be ruled out as they produce electron scattering optical depths for cosmic microwave background radiation which is higher than observational constraints.
