First Star Formation in the Presence of Primordial Magnetic Fields

TL;DR

This paper investigates how primordial magnetic fields influence the formation of the first stars, showing that fields generated during inflation could significantly delay or suppress early star formation, depending on their strength.

Contribution

It provides a detailed analysis of the effects of primordial magnetic fields on mini-halo collapse and star formation, highlighting the importance of the field's origin and strength.

Findings

Weak fields have modest effects on collapse timing.

Strong fields can delay or suppress mini-halo collapse.

Inflationary magnetic fields could significantly impact early star formation.

Abstract

It has been recently claimed that primordial magnetic fields could relieve the cosmological Hubble tension. We consider the impact of such fields on the formation of the first cosmological objects, mini-halos forming stars, for present-day field strengths in the range of $2\times 10^{-12}$ - $2\times 10^{-10}$ G. These values correspond to initial ratios of Alv\'en velocity to the speed of sound of $v_a/c_s\approx 0.03 - 3$. We find that when $v_a/c_s\ll 1$, the effects are modest. However, when $v_a\sim c_s$, the starting time of the gravitational collapse is delayed and the duration extended as much as by $\Delta$z = 2.5 in redshift. When $v_a > c_s$, the collapse is completely suppressed and the mini-halos continue to grow and are unlikely to collapse until reaching the atomic cooling limit. Employing current observational limits on primordial magnetic fields we conclude that inflationary produced primordial magnetic fields could have a significant impact on first star formation, whereas post-inflationary produced fields do not.