EVIDENCE FOR UBIQUITOUS HIGH-EQUIVALENT-WIDTH NEBULAR EMISSION IN z ∼ 7 GALAXIES: TOWARD A CLEAN MEASUREMENT OF THE SPECIFIC STAR-FORMATION RATE USING A SAMPLE OF BRIGHT, MAGNIFIED GALAXIES

Growing observational evidence indicates that nebular line emission has a significant impact on the rest-frame optical fluxes of z ~ 5-7 galaxies. In this paper, we present the most direct observational evidence thus far for ubiquitous high-equivalent-width (EW) [OIII] + H beta line emission in Lyman-break galaxies at z ~ 7, and we present a strategy for an improved measurement of the sSFR at z ~ 7. We accomplish this through the selection of bright galaxies in the narrow redshift window z ~ 6.6-7.0 where the Spitzer/Infrared Array Camera (IRAC) 4.5 mu m flux provides a clean measurement of the stellar continuum light, in contrast with the 3.6 mu m flux, which is contaminated by the prominent [OIII] + H beta lines. We can also set a robust lower limit of [gap]4 Gyr super(-1) on the sSFR of our sample based on the mean spectral energy distribution.