1 Introduction

The nonthermal radio continuum emission from the Galaxy at frequencies below 100 MHz is the synchrotron radiation of cosmic ray electrons with energies of order 1 GeV. Measurements of the emissivity and the spectral index of the emission provide direct information about the electron energy spectrum and the magnetic field strength in the Galaxy. At frequencies below about 40 MHz, the opacity of the thermal component of Galactic emission is often sufficient to absorb the much brighter background synchrotron emission, providing a means of estimating local synchrotron emissivities in the directions of H II regions at known distances.

There have been numerous surveys made of Galactic emission below 500 MHz including: the all-sky map of Haslam et al. (1982) at 408 MHz; the northern sky maps of Turtle & Baldwin (1962: 178 MHz, -5$^\circ$ to +90$^\circ$), of Milogradov-Turin & Smith (1973: 38 MHz, -25$^\circ$ to +70$^\circ$) and of Caswell (1976: 10 MHz, -6$^\circ$ to +74$^\circ$, $\rm 0^h$ to $\rm 16^h$); and southern sky maps of Landecker & Wielebinski (1970: 150 MHz and 85 MHz, -15$^\circ$ to +15$^\circ$), Hamilton & Haynes (1969: 153 MHz, +5$^\circ$ to -90$^\circ$), Alvarez et al. (1987: 45 MHz, +19$^\circ$ to -90$^\circ$), and Ellis (1982: 16.5 MHz, 0$^\circ$ to -90$^\circ$).

The 22 MHz Telescope at the DRAO was used in the period 1965 to 1969 to measure the emission from discrete sources and to map the background radiation from our galaxy. The telescope has been described completely by Costain et al. (1969); only those details relevant to the present paper are given here. Flux densities of point sources have been published by Roger et al. (1969) and by Roger et al. (1986). The low-frequency spectra of these sources have been discussed by Roger et al. (1973). Technical problems prevented a satisfactory calibration of the Galactic emission, but these problems have now been circumvented and in this paper we present a map of the Galactic emission at 22 MHz between declinations -28$^\circ$ and +80$^\circ$ covering the complete range of right ascension, $\sim$73%  of the sky. By comparing the 22 MHz map with the 408 MHz data from the all-sky survey of Haslam et al. (1982) we have prepared a map of the spectral index of the emission over the same area. We also derive values of the local synchrotron emissivity.