The Peas – Now detected in Radio!
Last September I blogged about a proposal that had just been accepted at the Giant Metrewave Radio Telescope (GMRT) to follow up on the Peas with radio observations. Now the observations are in, and we have successfully detected the Peas at radio wavelengths!
The Peas, which have very high star formation rates, are expected to host a large number of supernova, which are created when the most massive stars die. These supernova create shocks that accelerate electrons in galaxy to relativistic energies. These relativistic electrons emit a type of emission, synchrotron radiation, that is visible in radio wavelengths. Therefore, the radio emission can tell us about the stars that live (or lived) in the galaxy.
Three of the Peas from our paper (Cardamone et al. 2009), were followed up with deep observations using the GMRT. It turns out that the Peas have comparable, but systematically lower flux when compared to local starbursts.
Using the observed radio emission, the magnetic field of the galaxy can be derived. These new observations suggest a magnetic field in the peas similar to that of the Milky Way. Because galaxies are thought to build up their magnetic fields over time, it is surprising to see such a large magnetic field in such a young galaxy. (Estimates of the age of the stars in the Peas are roughly 1/100th that of the age of the stars in the Milky Way).
One of the reasons that the Peas are so fascinating is their similarities to vigorously star forming galaxies found in the early universe (known as Lyman Break Galaxies). These Lyman Break Galaxies are so far away, they haven’t yet been directly detected in radio emission. However, estimates of their radio flux (from a technique called ‘stacking’) also suggest consistent radio fluxes with those observed for the Peas.
These observations suggest that galaxies like the Peas (and the Lyman Break Galaxies), may start out early in their life with very large magnetic fields. These observations challenge the assumption that galaxies build up their magnetic fields slowly over time and it is another piece of the puzzel in understanding of how galaxies are formed.
The article will be coming soon to astro-ph and I will post it here to let you all know.