A Multiply Imaged Luminous Infrared Galaxy Behind the Bullet Cluster (1E0657-56)

Abstract

We present evidence for a Spitzer-selected luminous infrared galaxy (LIRG) behind the Bullet Cluster (1E0657-56). The galaxy, originally identified as a multiply imaged source using Infrared Array Camera (IRAC) photometry, has a spectral energy distribution consistent with a highly extincted (A_V ~ 3.3), strongly star forming galaxy at z = 2.7. Using our strong gravitational lensing model presented in a previous paper, we find that the magnifications are |μ| ≈ 10-50 for the three images of the galaxy. The brightest and faintest images differ by a factor of 3.2 in magnification. The implied infrared luminosity is consistent with the galaxy being a LIRG, with a stellar mass of M _* ~ 2 × 10¹⁰ M _sun and a star formation rate (SFR) of ~90 M _sun yr^-1. With lensed fluxes at 24 μm of 0.58 mJy and 0.39 mJy in the two brightest images, this galaxy presents a unique opportunity for detailed study of an obscured starburst with a SFR comparable to that of L* galaxies at z > 2.

This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, the Hubble Space Telescope, and the Spitzer Space Telescope.