A Selection of Giant Radio Sources from NVSS

TL;DR

This paper applies pattern recognition techniques, specifically decision trees, to identify Giant Radio Sources in the NVSS catalog, achieving high accuracy and producing a candidate list with morphological annotations for further study.

Contribution

It introduces a novel application of decision-tree classifiers to large radio source data, demonstrating high accuracy in GRS identification and providing a candidate catalog with morphological details.

Findings

Achieved 97.8% accuracy in ranking GRS candidates.

Generated a catalog of over 1,600 high-probability GRS candidates.

Demonstrated the importance of probability distribution comparison in classification.

Abstract

Results of the application of pattern recognition techniques to the problem of identifying Giant Radio Sources (GRS) from the data in the NVSS catalog are presented and issues affecting the process are explored. Decision-tree pattern recognition software was applied to training set source pairs developed from known NVSS large angular size radio galaxies. The full training set consisted of 51,195 source pairs, 48 of which were known GRS for which each lobe was primarily represented by a single catalog component. The source pairs had a maximum separation of 20 arc minutes and a minimum component area of 1.87 square arc minutes at the 1.4 mJy level. The importance of comparing resulting probability distributions of the training and application sets for cases of unknown class ratio is demonstrated. The probability of correctly ranking a randomly selected (GRS, non-GRS) pair from the best of the tested classifiers was determined to be 97.8 +/- 1.5%. The best classifiers were applied to the over 870,000 candidate pairs from the entire catalog. Images of higher ranked sources were visually screened and a table of over sixteen hundred candidates, including morphological annotation, is presented. These systems include doubles and triples, Wide-Angle Tail (WAT) and Narrow-Angle Tail (NAT), S- or Z-shaped systems, and core-jets and resolved cores. While some resolved lobe systems are recovered with this technique, generally it is expected that such systems would require a different approach.