Detection possibilities of hostless intergalactic supernova remnants with Square Kilometre Array

Abstract

Possibilities to detect hostless supernova remnants (hl-SNR) in intergalactic medium using the 1 GHz band of the Square Kilometre Array (SKA) are discussed. The optical detection rate of the hl-SN constrained from the Sloan Digital Sky Survey is used to predict a number of detectable hl-SNRs in the radio band. With an anticipated detection sensitivity (${\sim }\,1\,$ $\upmu$Jy) and angular resolution (${<}1''$) with the SKA, a significant number of hl-SNR are expected to get detected in the nearby galaxy groups, such as local group, Virgo, Fornax and Eridanus. A few very luminous hl-SNR may also be detected in the Coma cluster and other rich galaxy clusters up to about 100 Mpc distance. The identification of individual SNRs against other background radio sources will require sub-arcsec angular resolution at 1 GHz to resolve the characteristic circular morphology of the radio SNRs in nearby groups. At larger distances, where individual SNR cannot be resolved, a population of hl-SNR may also be constrained statistically in a small region, by estimating excess unresolved radio sources without a known optical host in a group or cluster, compared to the number density of the background radio sources at $\upmu$Jy flux level.