Constraints on ultracompact minihalos from extragalactic {\gamma}-ray background

TL;DR

This paper examines how ultracompact minihalos formed during early universe phase transitions contribute to the extragalactic gamma-ray background and uses Fermi-LAT data to set constraints on their abundance, surpassing CMB-based limits.

Contribution

It provides new constraints on UCMH abundance from gamma-ray observations, improving upon previous CMB-based limits, and explores their formation during multiple early universe phase transitions.

Findings

Fermi-LAT data yields more stringent UCMH abundance constraints than CMB.

UCMHs from phase transitions significantly contribute to gamma-ray background.

Constraints vary depending on the specific phase transition considered.

Abstract

It has been proposed that ultracompact minihalos (UCMHs) might be formed in earlier epoch. If dark matter consists of Weakly Interacting Massive Particles (WIMPs), UCMHs can be treated as the {\gamma}-ray sources due to dark matter annihilation within them. In this paper, we investigate the contributions of UCMHs formed during three phase transi- tions (i.e., electroweak symmetry breaking, QCD confinement and e+ e- annihilation) to the extragalactic {\gamma}-ray background. Moreover, we use the Fermi-LAT observation data of the extragalactic {\gamma}-ray background to get the constraints on the current abundance of UCMHs produced during these phase transitions. We also compare these results with those obtained from Cosmic Microwave Background (CMB) observations and find that the constraints from the Fermi-LAT are more stringent than those from CMB