Radio Galaxy Zoo: A Search for Hybrid Morphology Radio Galaxies

TL;DR

This study leverages citizen science through Radio Galaxy Zoo to identify 25 new hybrid morphology radio galaxies, revealing their diverse properties and potential formation mechanisms, and demonstrating the effectiveness of crowdsourcing in complex radio source classification.

Contribution

The paper presents the discovery of 25 new hybrid morphology radio galaxies using citizen science, expanding the known sample and analyzing their diverse characteristics and possible origins.

Findings

Identified 25 new hybrid morphology radio galaxy candidates.

Hybrid sources show diverse host types and sizes, including giant and cluster-centered galaxies.

Citizen scientists effectively pre-select complex radio sources for further study.

Abstract

Hybrid morphology radio sources are a rare type of radio galaxy that display different Fanaroff-Riley classes on opposite sides of their nuclei. To enhance the statistical analysis of hybrid morphology radio sources, we embarked on a large-scale search of these sources within the international citizen science project, Radio Galaxy Zoo (RGZ). Here, we present 25 new candidate hybrid morphology radio galaxies. Our selected candidates are moderate power radio galaxies (L_median = 4.7x10^{24} W/(Hz sr) at redshifts 0.14<z<1.0. Hosts of nine candidates have spectroscopic observations, of which six are classified as quasars, one as high- and two as low-excitation galaxies. Two candidate HyMoRS are giant (>1Mpc) radio galaxies, one resides at a centre of a galaxy cluster, and one is hosted by a rare green bean galaxy. Although the origin of the hybrid morphology radio galaxies is still unclear, this type of radio source starts depicting itself as a rather diverse class. We discuss hybrid radio morphology formation in terms of the radio source environment (nurture) and intrinsically occurring phenomena (nature; activity cessation and amplification), showing that these peculiar radio galaxies can be formed by both mechanisms. While high angular resolution follow-up observations are still necessary to confirm our candidates, we demonstrate the efficacy of the Radio Galaxy Zoo in the pre-selection of these sources from all-sky radio surveys, and report the reliability of citizen scientists in identifying and classifying complex radio sources.