The Host Galaxies of Hybrid Morphology Radio Sources

TL;DR

This study investigates hybrid morphology radio sources (HyMoRS) to determine if their unique structures are due to environmental factors and orientation, using multiwavelength data on host galaxies at intermediate redshifts.

Contribution

First multiwavelength analysis of HyMoRS host galaxies showing their properties align with typical FR-II hosts, supporting environment and orientation as causes of hybrid morphology.

Findings

HyMoRS hosts resemble typical FR-II galaxies.

Hybrid morphology likely caused by environment and orientation.

Results support the environmental and orientation hypothesis.

Abstract

Based on their differing radio morphologies, powerful radio galaxies can be separated into the Fanaroff-Riley I (FR-I) and II (FR-II) classes. Hybrid morphology radio sources (HyMoRS) contain morphologies consistent with each type of jet on either side: a powerful, highly relativistic FR-II-like jet terminating in a hotspot on one side and an FRI-like plume on the other. HyMoRS present a unique opportunity to study the conditions which give rise to the dichotomy. Using host galaxy properties, we conduct the first multiwavelength investigation into whether orientation can explain HyMoRS morphology. Through optical spectroscopy and mid-infrared photometry, we analyze the emission characteristics, and evaluate the broad characteristics of five HyMoRS host galaxies at intermediate redshifts (0.4 < z < 1.5). The HyMoRS host galaxies in our sample have properties consistent with typical host galaxies of FR-II sources, suggesting that the observed hybrid morphologies may be caused by a dense, cluster-like environment bending FR-II jets combined with a favorable orientation which can make one side appear similar to an FR-I jet. Our results thus support the hypothesis that HyMoRS are mainly caused by environment and orientation.