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2010MNRAS.405..887C - Mon. Not. R. Astron. Soc., 405, 887-897 (2010/June-3)
Starburst evolution: free-free absorption in the radio spectra of luminous IRAS galaxies.
CLEMENS M.S., SCAIFE A., VEGA O. and BRESSAN A.
Abstract (from CDS):
Several objects show radio spectra with two components having free-free turn-overs at different frequencies (including Arp220 and Arp299), indicating that synchrotron emission originates from regions with very different emission measures. In these sources, using a simple model for the supernova rate, we estimate the time for which synchrotron emission is subject to strong free-free absorption by ionized gas and compare this to expected Hii region lifetimes. We find that the ionized gas lifetimes are an order of magnitude larger than the plausible lifetimes for individual Hii regions. We discuss the implications of this result and argue that those sources which have a significant radio component with strong free-free absorption are those in which the star formation rate is still increasing with time.
We note that if ionization losses are important, the resulting curvature of the radio spectrum would much reduce the often observed deficit in fluxes above ∼10GHz.
Abstract Copyright: © 2010 The Authors. Journal compilation © 2010 RAS
Journal keyword(s): galaxies: active - infrared: galaxies - radio continuum: galaxies
Simbad objects: 38
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