The final candidate from the JVAS/CLASS search for 6 arcsec to 15 arcsec image separation lensing

TL;DR

This study investigates the final candidate from the JVAS/CLASS survey for 6 to 15 arcsec gravitational lensing, concluding it is not a lens but two separate active galactic nuclei, and finds no lenses in this separation range.

Contribution

The paper provides the first detailed optical follow-up of the last candidate, confirming the absence of gravitational lenses in the 6-15 arcsec range in JVAS/CLASS surveys.

Findings

The final candidate is not a gravitational lens but two separate AGNs.

No gravitational lenses with 6-15 arcsec separation found in JVAS/CLASS.

Results support the idea that group- and cluster-scale dark matter haloes are inefficient lenses.

Abstract

A search for 6 arcsec to 15 arcsec image separation lensing in the Jodrell Bank-Very Large Array Astrometric Survey (JVAS) and the Cosmic Lens All-Sky Survey (CLASS) by Phillips et al. found thirteen group and cluster gravitational lens candidates. Through radio and optical imaging and spectroscopy, Phillips et al. ruled out the lensing hypothesis for twelve of the candidates. In this paper, new optical imaging and spectroscopy of J0122+427, the final lens candidate from the JVAS/CLASS 6 arcsec to 15 arcsec image separation lens search, are presented. This system is found not to be a gravitational lens, but is just two radio-loud active galactic nuclei that are separated by ~10 arcsec on the sky and are at different redshifts. Therefore, it is concluded that there are no gravitational lenses in the JVAS and CLASS surveys with image separations between 6 arcsec to 15 arcsec. This result is consistent with the expectation that group- and cluster-scale dark matter haloes are inefficient lenses due to their relatively flat inner density profiles.