All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz^⋆

A. E. Guzmán¹, J. May¹, H. Alvarez¹ and K. Maeda²

¹ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
e-mail: aguzman@das.uchile.cl
² Hyogo University of Health Sciences, Japan

Received: 9 November 2009
Accepted: 27 October 2010

Abstract

Aims. We study the Galactic large-scale synchrotron emission by generating a reliable all-sky spectral index map and temperature map at 45 MHz.

Methods. We use our observations, the published all-sky map at 408 MHz, and a bibliographical compilation to produce a map corrected for zero-level offset and extragalactic contribution.

Results. We present full sky maps of the Galactic emission at 45 MHz and the Galactic spectral index between 45 and 408 MHz with an angular resolution of 5°. The spectral index varies between 2.1 and 2.7, reaching values below 2.5 at low latitude because of thermal free-free absorption and its maximum in the zone next to the Northern Spur.