Searching for primordial helical magnetic fields

TL;DR

This paper investigates the potential for detecting primordial helical magnetic fields through gamma-ray observations, concluding that current data shows no significant evidence and detection remains challenging with existing models.

Contribution

It extends previous gamma-ray data analysis to over 11 years and assesses the prospects of detecting primordial helical magnetic fields using individual sources.

Findings

No significant evidence for helical magnetic fields in 2.5-year data.

Detection prospects are limited with current models and detector capabilities.

A hint in earlier data was a statistical fluctuation.

Abstract

The presence of non-zero helicity in intergalactic magnetic fields (IGMF) has been suggested as a clear signature for their primordial origin. We extend a previous analysis of diffuse Fermi-LAT gamma-ray data from 2.5 to more than 11 years and show that a hint for helical magnetic fields in the 2.5 year data was a statistical fluctuation. Then we examine the detection prospects of helical magnetic fields using individual sources as, e.g., TeV gamma-ray blazars. We find that a detection is challenging employing realistic models for the cascade evolution, the IGMF and the detector resolution in our simulations.