Discovery of A Very Bright, Strongly-Lensed z=2 Galaxy in the SDSS DR5

TL;DR

This paper reports the discovery and analysis of a very bright, strongly-lensed galaxy at redshift 2, providing valuable data for studying high-redshift star formation and galaxy properties.

Contribution

The paper presents the first systematic search for bright lensed galaxies in SDSS DR5 and confirms the lensing nature with follow-up observations, including a simple lens model and physical property estimates.

Findings

Lens model yields Einstein radius of 3.82 arcsec

Total mass within Einstein radius is 2.10 x 10^12 M_sun/h

Unlensed star formation rate is approximately 32 M_sun/yr

Abstract

We report on the discovery of a very bright z = 2.00 star-forming galaxy that is strongly lensed by a foreground z=0.422 luminous red galaxy (LRG). This system was found in a systematic search for bright arcs lensed by LRGs and brightest cluster galaxies in the Sloan Digital Sky Survey Data Release 5 sample. Follow-up observations on the Subaru 8.2m telescope on Mauna Kea and the Astrophysical Research Consortium 3.5m telescope at Apache Point Observatory confirmed the lensing nature of this system. A simple lens model for the system, assuming a singular isothermal ellipsoid mass distribution, yields an Einstein radius of 3.82 +/- 0.03 arcsec or 14.8 +/- 0.1 kpc/h at the lens redshift. The total projected mass enclosed within the Einstein radius is 2.10 +/- 0.03 x 10^12 M_sun/h, and the magnification factor for the source galaxy is 27 +/- 1. Combining the lens model with our gVriz photometry, we find an (unlensed) star formation rate for the source galaxy of 32 M_sun/h / yr, adopting a fiducial constant star formation rate model with an age of 100 Myr and E(B-V) = 0.25. With an apparent magnitude of r = 19.9, this system is among the very brightest lensed z >= 2 galaxies, and provides an excellent opportunity to pursue detailed studies of the physical properties of an individual high-redshift star-forming galaxy.