Bursty star formation during the Cosmic Dawn driven by delayed stellar feedback

In recent years, several analytic models have demonstrated that simple assumptions about halo growth and feedback-regulated star formation can match the (limited) existing observational data on galaxies at z >= 6. By extending such models, we demonstrate that imposing a time delay on stellar feedback (as inevitably occurs in the case of supernova explosions) induces burstiness in small galaxies. Although supernova progenitors have short lifetimes (similar to 5-30 Myr), the delay exceeds the dynamical time of galaxies at such high redshifts. As a result, star formation proceeds unimpeded by feedback for several cycles and 'overshoots' the expectations of feedback-regulated star formation models. We show that such overshoot is expected even in atomic cooling haloes, with halo masses up to similar to 10(10.5) M-circle dot at z greater than or similar to 6. However, these burst cycles damp out quickly in massive galaxies, because large haloes are more resistant to feedback so retain a continuous gas supply. Bursts in small galaxies - largely beyond the reach of existing observations - induce a scatter in the luminosity of these haloes (of similar to 1 mag) and increase the time-averaged star formation efficiency by up to an order of magnitude. This kind of burstiness can have substantial effects on the earliest phases of star formation and reionization.

Automated summary

In recent years, analytic models have shown that simple assumptions about halo growth and feedback-regulated star formation can match existing observational data on galaxies at z >= 6. By extending these models, it has been demonstrated that stellar feedback time delay caused by supernova explosions leads to burstiness in small galaxies. However, these burst cycles damp out quickly in massive galaxies due to their ability to resist feedback.