Asymmetry in the variability of radio sources towards the centre and anti-centre of the galaxy

Abstract

We report an asymmetry in the distribution of low frequency variable (LFV) radio sources towards the centre-anticentre regions of our galaxy. The study is based on 15 years' monitoring of a large sample of sources observed with Culgoora Array at 80 and 160 MHz. This asymmetry is in marked contrast with the symmetrical distribution of non-variable sources from the same sample. Median values of the corresponding modulation indices on both short and long time scales also show a statistically significant increase towards the Galactic centre compared with the anticmtre region.These results strongly suggest that LFV has an interstellar origin and that the most likely mechanism is refractive scintillation.

From the Solar Corona to Clusters of Galaxies: The Radio Astronomy of Bruce Slee

“…This paper contained all sources listed in the Culgoora-1, 2 and 3 papers plus additional sources detected in the course of a survey of various Abell clusters of galaxies, and for further ease of access all data were made available in electronic form. In 1995, Slee and two Russian colleagues also investigated the asymmetrical distribution in the centreanticentre region of variable radio sources detected during the Culgoora surveys (Shapirovskaya, Slee and Tsarevsky, 1995).…”