SDSS J094604.90+183541.8: A Gravitationally Lensed Quasar at z=4.8

TL;DR

This paper reports the discovery of the highest redshift known gravitationally lensed quasar at z=4.8, including imaging, spectroscopic confirmation, and lens modeling, highlighting its significance for quasar surveys.

Contribution

The paper presents the first identification and detailed analysis of a z=4.8 gravitationally lensed quasar, expanding the known redshift range of such objects.

Findings

Discovered a z=4.8 lensed quasar with two images separated by 3.06 arcsec.

Confirmed the lensing nature through spectroscopy and modeling.

Estimated a total magnification of 3.2 for the quasar images.

Abstract

We report the discovery of a gravitationally lensed quasar identified serendipitously in the Sloan Digital Sky Survey (SDSS). The object, SDSS J094604.90+183541.8, was initially targeted for spectroscopy as a luminous red galaxy, but the SDSS spectrum has the features of both a z=0.388 galaxy and a z=4.8 quasar. We have obtained additional imaging that resolves the system into two quasar images separated by 3.06 arcsec and a bright galaxy that is strongly blended with one of the quasar images. We confirm spectroscopically that the two quasar images represent a single lensed source at z=4.8 with a total magnification of 3.2, and we derive a model for the lensing galaxy. This is the highest redshift lensed quasar currently known. We examine the issues surrounding the selection of such an unusual object from existing data and briefly discuss implications for lensed quasar surveys.