Radio spectral index study of the SNRs OA184 and VRO42.05.01

Free access article

This article has an erratum: [erratum]

Issue		A&A Volume 440, Number 3, September IV 2005


Page(s)		929 - 936
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20053392

A&A 440, 929-936 (2005)
DOI: 10.1051/0004-6361:20053392

Radio spectral index study of the SNRs OA184 and VRO42.05.01

D. Leahy¹ and W. Tian^{1, 2}

¹ Department of Physics & Astronomy, University of Calgary, Calgary, Alberta T2N 1N4, Canada
e-mail: wtian@ucalgary.ca
² National Astronomical Observatories, CAS, Beijing 100012, PR China

(Received 10 May 2005 / Accepted 2 June 2005)

Abstract
New images of the Supernova Remnants (SNRs) OA184 and VRO42.05.01 are presented at 408 MHz and 1420 MHz, from the Canadian Galactic Plane Survey (CGPS) data. The SNRs' flux densities at both 408 MHz and 1420 MHz are found and corrected for flux densities from compact sources within the SNRs. The integrated flux density based spectral indices (S $_{\nu}\propto\nu^{-\alpha}$ ) are 0.25 $\pm$ 0.03 for OA184 and 0.36 $\pm$ 0.06 for VRO42.05.01. These agree with the respective T-T plot spectral indexes of 0.23 $\pm$ 0.06 and 0.36 $\pm$ 0.03. OA184's spectral index is smaller than previously published values. The older flux density values of OA184 from lower resolution data include contributions from a non-SNR ridge emission region and from compact sources within OA184. Subtracting these contributions results in a spectral index of 0.32 $\pm$ 0.06 (38 MHz to 2695 MHz) or 0.28 $\pm$ 0.06 (408 MHz to 2695 MHz). Correction of published flux densities for compact sources for VRO.42.05.01 results in a spectral index of 0.32 $\pm$ 0.05 for 38 MHz to 2695 MHz. We also find spatial variations of spectral index. For OA184 $\alpha$ varies from 0.1 to 0.3 (with errors $\simeq$ 0.1). For VRO42.05.01, the shell region has $\alpha=0.31$ and the wing region has $\alpha=0.47$ (with errors $\simeq$ 0.03).

Key words: ISM: supervona remnants -- ISM: structure

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