UCLA

We obtained mid-infrared 3.6 and 4.5μm imaging of a z = 6.96 Lyα emitter (LAE), IOK-1, discovered in the Subaru Deep Field, using Spitzer Space Telescope Infrared Array Camera observations. After removal of a nearby bright source, we found that IOK-1 is not significantly detected in any of these infrared bands to m3:6μm ∼ 24.00 and m4:5μm ∼ 23.54 at 3φ. Fitting population synthesis models to the spectral energy distribution consisting of the upper limit fluxes of the optical-to-infrared non-detection images and fluxes in detection images, we constrained the stellar mass, M*, of IOK-1. This LAE could have either a mass as low as M* . ≤2-9 × 108 M for young age (≤10 Myr) and low dust reddening (AV ∼ 0) or a mass as large as M* . 1-4 × 1010 M for either old age (>100 Myr) or high dust reddening (AV ∼ 1.5). This would be within the range of masses of z ∼ 3-6.6 LAEs studied to date, ∼106-10 10M. Hence, IOK-1 is not a particularly unique galaxy with extremely high mass or low mass, but is similar to one of the LAEs seen at later epochs. © 2010. Astronomical Society of Japan.