Upper limits on the infrared flux density of the ‘filled-centre’ supernova remnant 3C58

Abstract

Upper limits of 0.4, 0.4, 0.8 and 1.5 Jy for the infrared flux density of the ‘filled-centre’ supernova remnant 3C58 are derived from IRAS observations at 12, 25, 60 and 100 μm respectively. These limits are considerably below the infrared flux densities predicted for 3C58 by Reynolds & Chevalier. They are consistent with a break in the spectrum of 3C58 at ≈ 50 GHz, which is two orders of magnitude below the break in the spectrum of the Crab nebula. The change of spectral index across the break for 3C58 is more than 0.5, which implies that the emission from 3C58 is not dominated by a constant injection rate of particles with a power-law distribution. Either the break is intrinsic to the acceleration mechanism at work – presumably from a central neutron star – or it is due to synchrotron losses in the past, with little if any particle injection in recent times.