Oral Presentation

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

Author(s): Kenneth Wong (ASIAA), K.-V. Tran (Texas A&M) S. Suyu (ASIAA), I. Momcheva (Yale), G. Brammer (STScI), M. Brodwin (UMKC), A. Gonzalez (Florida), A. Halkola, G. Kacprzak (Swinburne), A. Koekemoer (STScI), C. Papovich (Texas A&M), G. Rudnick (Kansas)

Presenter: Kenneth Wong (ASIAA)

We identify a strong lensing galaxy in the cluster IRC 0218 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 HST grism and Keck/LRIS spectroscopy, we measure the source redshift to be z = 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 0.38" (~3.2 kpc) and the total enclosed mass is 1.8 x 10^11 solar masses. We estimate that the cluster environment contributes ~10% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within the Einstein radius is f_DM ~ 0.3, while a Salpeter IMF is marginally inconsistent with the enclosed mass (f_DM ~ -0.3). The source has at least one bright compact region offset from the source center. Emission from Lyman alpha and [O III] may also probe different regions in the source.