Ultraviolet-bright, High-Redshift Ultraluminous Infrared Galaxies

We present Spitzer Space Telescope observations of the z = 2.38 Lya emitter overdensity associated with galaxy cluster J2143-4423, the largest known structure (110 Mpc) above z = 2. We imaged 22 of the 37 known Lya emitters within the filament-like structure, using the MIPS 24 km band. We detected six of the Lya emitters, including three of the four clouds of extended (>50 kpc) Lya emission, also known as Lya blobs. Conversion from a rest wavelength of 7 km to total far-infrared luminosity using locally derived correlations suggests that all the detected sources are in the class of ultraluminous infrared galaxies (ULIRGs), with some reaching hyper-LIRG energies. Lya blobs frequently show evidence of interaction, either in HST imaging or in the proximity of multiple MIPS sources within the Lya cloud. This connection suggests that interaction or even mergers may be related to the production of Lya blobs. A connection to mergers does not in itself help explain the origin of the Lya blobs, as most of the suggested mechanisms for creating Lya blobs (starbursts, active galactic nuclei, cooling flows) could also be associated with galaxy interactions.