Separation of galactic and extragalactic radio emission at decameter wavelengths

Abstract

We present the results of separation of observed radio emission at decameter wavelengths into extragalactic background and halo components of the Galaxy. We have used a multifrequency UTR-2 (decametric wave radio telescope) survey to perform multifrequency temperature-versus-temperature (T-T) plots. The low-frequency radio maps of the area near the minimum of Galactic radiation $(41^{\circ } < \delta_{2000} < 46^{\circ }, 7^{\mathrm{h}} 45^{\mathrm{m}} < \alpha_{2000} < 8^{\mathrm{h}} 35^{\mathrm{m}}) $ has been investigated in detail. The differential spectral index of the Galaxy halo at the frequencies 14.7, 16.7, 20, and 25 MHz was determined in this direction using pairwise of all the above frequencies. Its value was found to be $\beta_{G} = 2.81 \pm 0.03 $ . In addition, using the multifrequency T-T plots, the integral extragalactic brightness temperatures of isotropic background were determined to range 12 kK at 25 MHz to 42 kK at 14.7 MHz, and the extragalactic spectral index $\beta_{E} = 2.41 \pm 0.1 $ .