Imaging of SNR IC443 and W44 with the Sardinia Radio Telescope at 1.5 GHz and 7 GHz

Abstract

Observations of supernova remnants (SNRs) are a powerful tool for investigating the later stages of stellar evolution, the properties of the ambient interstellar medium, and the physics of particle acceleration and shocks. For a fraction of SNRs, multi-wavelength coverage from radio to ultra high-energies has been provided, constraining their contributions to the production of Galactic cosmic rays. Although radio emission is the most common identifier of SNRs and a prime probe for refining models, high-resolution images at frequencies above 5 GHz are surprisingly lacking, even for bright and well-known SNRs such as IC443 and W44. In the frameworks of the Astronomical Validation and Early Science Program with the 64-m single-dish Sardinia Radio Telescope, we provided, for the first time, single-dish deep imaging at 7 GHz of the IC443 and W44 complexes coupled with spatially-resolved spectra in the 1.5-7 GHz frequency range. Our images were obtained through on-the-fly mapping techniques, providing antenna beam oversampling and resulting in accurate continuum flux density measurements. The integrated flux densities associated with IC443 are S_1.5GHz = 134 +/- 4 Jy and S_7GHz = 67 +/- 3 Jy. For W44, we measured total flux densities of S_1.5GHz = 214 +/- 6 Jy and S_7GHz = 94 +/- 4 Jy. Spectral index maps provide evidence of a wide physical parameter scatter among different SNR regions: a flat spectrum is observed from the brightest SNR regions at the shock, while steeper spectral indices (up to 0.7) are observed in fainter cooling regions, disentangling in this way different populations and spectra of radio/gamma-ray-emitting electrons in these SNRs.

13 pages, 9 figures, accepted for publication to MNRAS on 18 May 2017

References in corpus (6)

• Detection of the Characteristic Pion-Decay Signature in Supernova Remnants
• The origin of galactic cosmic rays
• The low frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz
• XMM-Newton observations of the supernova remnant IC 443: II. evidence of stellar ejecta in the inner regions
• The Supernova Remnant W44: confirmations and challenges for cosmic-ray acceleration
• Modeling Bright Gamma-ray and Radio Emission at Fast Cloud Shocks

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• An International Survey of Front-End Receivers and Observing Performance of Telescopes for Radio Astronomy
• New high-frequency radio observations of the Cygnus Loop supernova remnant with the Italian radio telescopes
• Interstellar anatomy of the TeV gamma-ray peak in the IC443 supernova remnant
• Solar observations with single-dish INAF radio telescopes: continuum imaging in the 18-26 GHz range
• QUIJOTE scientific results -- V. The microwave intensity and polarisation spectra of the Galactic regions W49, W51 and IC443
• Methods for detection and analysis of weak radio sources with single-dish radio telescopes
• Limits on compression of cosmic rays in supernova remnants
• Broadband radio study of the supernova remnant Kes 73