# Feedback from first radiation sources: H- photodissociation

## TL;DR

This paper investigates how H- photodissociation during reionization affects molecular hydrogen formation and star formation in early galaxies, potentially delaying reionization.

## Contribution

It provides a quantitative estimate of H- photodissociation's impact on H2 formation across different radiation sources during reionization.

## Key findings

- H- photodissociation reduces H2 formation by a factor depending on ionized fraction and escape fraction.
- Significant H2 reduction may delay primordial star formation and reionization.
- The impact varies with source type and local gas conditions.

## Abstract

During the epoch of reionization, the formation of radiation sources is accompanied by the growth of a H- photodissociating flux. We estimate the impact of this flux on the formation of molecular hydrogen and cooling in the first galaxies, assuming different types of radiation sources (e.g. Pop II and Pop III stars, miniquasars). We find that H- photodissociation reduces the formation of H2 molecules by a factor of ~1+1000k_s*x/(f_esc*delta), where x is the mean ionized fraction in the IGM, f_esc is the fraction of ionizing photons that escape from their progenitor halos, delta is the local gas overdensity and k_s is an order unity constant which depends on the type of radiation source. By the time a significant fraction of the universe becomes ionized, H- photodissociation may significantly reduce the H2 abundance and, with it, the primordial star formation rate, delaying the progress of reionization.