Quasar Radio Morphology and Environment at z ≃ 1/2

Abstract

The radio morphology of thirty radio-loud quasars at z ≃ 1/2 is studied as a function of cluster galaxy density using data available in the literature. While correlations between several morphological parameters of the radio emission are consistent with interactions with an intracluster medium (ICM), we do not see the correlation between galaxy density and quasar radio morphology expected from ICM interaction. Therefore, distorted radio morphology is not an indicator for the presence of a distant cluster as previously suggested. Because such correlations are found at z ≃ 0, these results are suggestive that the rich clusters containing quasars at z ≃ 1/2 have not yet developed a dense ICM. An inelastic collision with neighboring galaxies and intergalactic clouds can account for the morphology of several of the sources in this sample and is a viable alternative explanation.