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