SDSS J120923.7+264047: A new massive galaxy cluster with a bright giant arc

TL;DR

This paper reports the discovery of a new massive galaxy cluster, SDSS J120923.7+264047, which acts as a gravitational lens producing bright arcs, including one of the brightest known lensed galaxies at redshift 1.018, enabling detailed high-resolution studies.

Contribution

The paper introduces a newly identified galaxy cluster with strong lensing features and a notably bright lensed galaxy, expanding the sample of such systems for detailed astrophysical analysis.

Findings

Discovery of a new massive lensing cluster at z=0.558.

Identification of multiple arcs, including a bright galaxy at z=1.018.

First low-resolution spectrum of the brightest arc obtained.

Abstract

Highly magnified lensed galaxies allow us to probe the morphological and spectroscopic properties of high-redshift stellar systems in great detail. However, such objects are rare, and there are only a handful of lensed galaxies which are bright enough for a high-resolution spectroscopic study with current instrumentation. We report the discovery of a new massive lensing cluster, SDSS J120923.7+264047, at z=0.558. Present around the cluster core, at angular distances of up to ~40'', are many arcs and arc candidates, presumably due to lensing of background galaxies by the cluster gravitational potential. One of the arcs, 21'' long, has an r-band magnitude of 20, making it one of the brightest known lensed galaxies. We obtained a low-resolution spectrum of this galaxy, using the Keck-I telescope, and found it is at redshift of z=1.018.