High-$z$ Universe probed via Lensing by QSOs (HULQ) II. Deep GMOS spectroscopy of a QSO lens candidate

TL;DR

This study investigates a QSO lens candidate using deep spectroscopy, finding it is not a lens, and discusses implications for black hole and galaxy coevolution based on lens search results.

Contribution

First spectroscopic analysis of a QSO lens candidate from HULQ, providing insights into lensing occurrence and future research directions.

Findings

HULQ J0002+0239 is not a QSO lens.

Spectroscopic data revealed two galaxies at different redshifts.

Results align with predicted QSO lens numbers.

Abstract

Galaxies and their central supermassive black holes are known to coevolve, but the physical background for this is unknown as of yet. The High-$z$ Universe probed via Lensing by QSOs (HULQ) project aims to investigate this coevolution by using quasi-stellar object (QSO) host galaxies acting as gravitational lenses (QSO lenses). We present the results of the spectroscopic observation of the first QSO lens candidate from the HULQ project, HULQ J0002+0239, which consists of a QSO host galaxy at $z_{\rm d} = 1.455$ and four seemingly lensed objects in a cross-like configuration. Deep optical spectra of two of the possibly lensed objects with $z \sim 24.5$ mag were obtained with the Gemini Multi-Object Spectrograph on the Gemini North Telescope. Their spectra reveal that the objects are newly discovered galaxies at $z=0.29$ and $z=1.11$, and we conclude that HULQ J0002+0239 is not a QSO lens. Our QSO lens search results are so far in agreement with the predicted number of QSO lenses, and we discuss how the future investigation of additional QSO lens candidates could tell us more about the evolution of the black hole mass and host galaxy scaling relations.