Discovery of a Strong Lensing Galaxy Embedded in a Cluster at z = 1.62

Abstract

We identify a strong lensing galaxy in the cluster IRC 0218 (also known as XMM-LSS J02182$-$05102) that is spectroscopically confirmed to be at $z=1.62$, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope (HST) grism and Keck/LRIS spectroscopy, we measure the source redshift to be $z_{\mathrm{S}}=2.26$. Using HST imaging in ACS/F475W, ACS/F814W, WFC3/F125W, and WFC3/F160W, we model the lens mass distribution with an elliptical power-law profile and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is ${\theta }_{\mathrm{E}}=0.38_{-0.01}^{+0.02}$" ($3.2_{-0.1}^{+0.2}$ kpc) and the total enclosed mass is M${}_{\mathrm{tot}}(<{\theta }_{\mathrm{E}})=1.8_{-0.1}^{+0.2}\times 10^{11}{\mathrm{M}}_{\odot }$. We estimate that the cluster environment contributes $\sim 10$% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within ${\theta }_{\mathrm{E}}$ is $f_{\mathrm{DM}}^{\mathrm{Chab}}=0.3_{-0.3}^{+0.1}$, while a Salpeter IMF is marginally inconsistent with the enclosed mass ($f_{\mathrm{DM}}^{\mathrm{Salp}}=-0.3_{-0.5}^{+0.2}$). The total magnification of the source is ${\mu }_{\mathrm{tot}}=2.1_{-0.3}^{+0.4}$. The source has at least one bright compact region offset from the source center. Emission from Ly$\alpha$ and [O III] are likely to probe different regions in the source.

Accepted for publication in ApJL; emulateapj format; 6 pages, 3 figures, 1 table

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• The COSMOS-Web ring: in-depth characterization of an Einstein ring lensing system at z~2
• J1721+8842: The first Einstein zig-zag lens
• Lower mass normalization of the stellar initial mass function for dense massive early-type galaxies at z ~ 1.4
• The COSMOS-Web ring: Spectroscopic confirmation of the background source at z = 5.1
• Schwarzschild Lensing From Geodesic Deviation
• Optical+NIR analysis of a Newly Confirmed Einstein ring at z$\sim$1 from the Kilo-Degree Survey: Dark matter fraction, total and dark matter density slope and IMF
• Many body gravity and the bullet cluster
• Many body gravity and the galaxy rotation curves
• Milky-Way-like stars in a galaxy core 8 billion years ago revealed by gravitational lensing
• The AGEL Survey: Spectroscopic Confirmation of Strong Gravitational Lenses in the DES and DECaLS Fields Selected Using Convolutional Neural Networks