Radio Detection of Green Peas: Implications for Magnetic Fields in Young Galaxies

TL;DR

This study reports the first radio detection of Green Pea galaxies, revealing they possess strong magnetic fields (>30 μG) that challenge current models of magnetic field growth in young galaxies.

Contribution

It provides the first direct radio evidence of magnetic fields in Green Pea galaxies, supporting the existence of pregalactic magnetic fields.

Findings

Green Pea galaxies have magnetic fields >30 μG.

Radio emission indicates early magnetic field amplification.

Results challenge dynamo-based magnetic field growth models.

Abstract

Green Peas are a new class of young, emission line galaxies that were discovered by citizen volunteers in the Galaxy Zoo project. Their low stellar mass, low metallicity and very high star formation rates make Green Peas the nearby (z~0.2) analogs of the Lyman-break Galaxies (LBGs) which account for the bulk of the star formation in the early universe (z~2-5). They thus provide accessible laboratories in the nearby Universe for understanding star formation, supernova feedback, particle acceleration and magnetic field amplification in early galaxies. We report the first direct radio detection of Green Peas with low frequency GMRT observations and our stacking detection with archival VLA FIRST data. We show that the radio emission implies that these extremely young galaxies already have magnetic fields (>30 muG) even larger than that of the Milky Way. This is at odds with the present understanding of magnetic field growth based on amplification of seed fields by dynamo action over a galaxy's lifetime. Our observations strongly favor models with pregalactic magnetic fields at muG levels.