Two lensed Lyman-α emitting galaxies at z ∼ 5

Abstract

We present observations of two strongly lensed z ∼ 5 Lyman-α emitting galaxies that were discovered in the Sloan Giant Arcs Survey (SGAS). We identify the two sources as SGAS J091541+382655 at z = 5.200 and SGAS J134331+415455 at z = 4.994. We measure their AB magnitudes at (i, z) = (23.34 ± 0.09, 23.29 ± 0.13) mag and (i, z) = (23.78 ± 0.18, 24.24+0.18-0.16) mag and the rest-frame equivalent widths of the Lyman-α emission at 25.3 ± 4.1 Å and 135.6 ± 20.3 Å for SGAS J091541+382655 and SGAS J134331+415455, respectively. Each source is strongly lensed by a massive galaxy cluster in the foreground, and the magnifications due to gravitational lensing are recovered from strong lens modeling of the foreground lensing potentials. We use the magnification to calculate the intrinsic, unlensed Lyman-α and UV continuum luminosities for both sources, as well as the implied star formation rates. We find SGAS J091541+382655 and SGAS J134341+415455 to be galaxies with (L Ly-α, LUV) ≤ (0.6 L*Ly-α, 2L*UV) and (L Ly-α, LUV) = (0.5 L*Ly-α, 0.9 L*UV), respectively. Comparison of the spectral energy distributions of both sources against stellar population models produces estimates of the mass in young stars in each galaxy; we report an upper limit of Mstars ≤ 7.9+3.7-2.5 × 107 M⊙h-10.7 for SGAS J091531+382655 and a range of viable masses for SGAS J134331+415455 of 2 × 108 M⊙h-10.7 < Mstars < 6 × 109M ⊙ h-10.7. © 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.