Effect of Cosmic UV Background on Star Formation in High Redshift Galaxies

TL;DR

This study uses high-resolution cosmological simulations to show that the cosmic UV background has negligible impact on star formation in high redshift galaxies, as local radiation dominates.

Contribution

It demonstrates through detailed simulations that local radiation fields outweigh the cosmic UV background in influencing star formation in early galaxies.

Findings

Local radiation field dominates over cosmic UV background by a factor of 100

Cosmic UV background is irrelevant for star formation in normal high redshift galaxies

Simulations resolve molecular cloud formation sites with high spatial resolution

Abstract

The effect of the cosmic UV background on star formation in high redshift galaxies is explored by means of high resolutions cosmological simulations. The simulations include star formation, 3D radiative transfer, and a highly detailed ISM model, and reach spatial resolution sufficient to resolve formation sites for molecular clouds. In the simulations the local radiation field in the Lyman-Werner band around star-forming molecular clouds dominates over the cosmic UV background by a factor of 100, similarly to the interstellar radiation field in the Milky Way and in a few high redshift galaxies for which measurements exist. The cosmic UV background, therefore, is essentially irrelevant for star formation in normal galaxies.