Spitzer Identifications and Classifications of Submillimeter Galaxies in Giant, High-redshift Lyman-α Emission-line Nebulae

Using Spitzer Space Telescope IRAC (3.6–8μm) and MIPS (24μm) imaging, as well as Hubble Space Telescope optical observations, we identify the IRAC counterparts of the luminous power sources residing within the two largest and brightest Lyman-α emitting nebulae (LABs) in the SA 22 protocluster at z = 3.09 (LAB 1 and LAB 2). These sources are also both submillimeter galaxies (SMGs). From their rest-frame optical/nearinfrared colors, we conclude that the SMG in LAB 1 is likely to be starburst dominated and heavily obscured (AV ∼ 3). In contrast, LAB 2 has excess rest-frame∼2μm emission (over that expected from starlight) and hosts a hard X-ray source at the proposed location of the SMG, consistent with the presence of an active galactic nucleus (AGN). We conclude that LAB 1 and LAB 2 appear to have very different energy sources despite having similar Lyman-α spatial extents and luminosities, although it remains unclear whether on-going star-formation or periodic AGN heating is responsible for the extended Lyman-α emission. We find that the mid-infrared properties of the SMGs lying in LAB 1 and LAB 2 are similar to those of the wider SMG population, and so it is possible that extended Lyman-α haloes are a common feature of SMGs in general. Subject headings: galaxies: active — galaxies: high-redshift — infrared: galaxies