Spectral Index of the Diffuse Radio Background Measured From 100 to 200 MHz

TL;DR

This study measures the diffuse radio background's brightness temperature across 100-200 MHz, deriving a spectral index that informs models of the Galactic and extragalactic radio emission.

Contribution

It provides new precise measurements of the spectral index of the diffuse radio background between 100 and 200 MHz, including systematic error estimates.

Findings

Spectral index beta = 2.5 +/- 0.1 between 100-200 MHz

Brightness temperature at 150 MHz is 237 +/- 10 K

Spectral index between 150 and 408 MHz is beta = 2.52 +/- 0.04

Abstract

The mean absolute brightness temperature of the diffuse radio background was measured as a function of frequency in a continuous band between 100 and 200 MHz over an effective solid angle of ~pi str at high Galactic latitude. A spectral brightness temperature index of beta = 2.5 +/- 0.1 (alpha_s = 0.5) was derived from the observations, where the error limits are 3-sigma and include estimates of the instrumental systematics. Zenith drift scans with central declinations of -26.5 degrees and spanning right ascensions 0 to 10 hours yielded little variation in the mean spectral index. The mean absolute brightness temperature at 150 MHz was found to reach a minimum of T = 237 +/- 10 K at a right ascension of 2.5 hours. Combining these measurements with those of Haslam et al. 1982 yields a spectral index of beta = 2.52 +/- 0.04 between 150 and 408 MHz.