Study of Bright Compact Radio Sources of the Northern Hemisphere at the frequency of 111 MHz

TL;DR

This study used interplanetary scintillation to identify and analyze compact radio sources in the northern hemisphere at 111 MHz, estimating their sizes and fluxes, and examining effects of solar activity on measurements.

Contribution

It presents a large-scale survey of compact radio sources at 111 MHz using scintillation, including size estimates and analysis of solar activity influence, which is novel at this frequency.

Findings

812 sources found to have compact components.

Maximum scintillation index decreases with flux, no size-flux dependence.

Solar activity influences angular size estimates.

Abstract

The search for compact components of strong ($S_{int} \ge 5$ Jy at 102.5 MHz) discrete radio sources from the Pushchino catalogue was carried out using the method of interplanetary scintillation. A total of 3620 sources were examined, and 812 of them were found to compact (scintillating) components. Estimates of fluctuations of the flux density of these compact components were derived from the scintillation index ($m_{max}$) corresponding to an elongation of $25^o$. The angular size and compactness of 178 sources with compact components were estimated. Scintillation indices of sources corresponding to the compact component ($m_{max}$) and flux densities of compact components were determined. It was demonstrated that slow variations of the spatial distribution of interplanetary plasma, which are related to the 11-year cycle of solar activity, may exert a systematic influence on the estimates of angular sizes of sources. Coefficients compensating the deviation from the spherical symmetry of solar wind in the estimates of angular sizes were found using the coefficient of asymmetry of the statistical distribution of intensity fluctuations. The study of correlations between the parameters of sources in the sample revealed that the maximum value of the scintillation index decreases as the integrated flux increases, while the angular size has no marked dependence on the integrated flux.