Identification of luminous infrared galaxies at 1 ≲ z ≲ 2.5

We present preliminary results on 24 μm detections of luminous infrared galaxies at z ≳ 1 with the Multiband Imaging Photometer for Spitzer (MIPS). Observations were performed in the Lockman Hole and the Extended Groth Strip (EGS) and were supplemented by data obtained with the Infrared Array Camera (IRAC) between 3 and 9 μm. The positional accuracy of ≲2″ for most MIPS/IRAC detections provides unambiguous identifications of their optical counterparts. Using spectroscopic redshifts from the Deep Extragalactic Evolutionary Probe survey, we identify 24 μm sources at z ≳ 1 in the EGS, while the combination of the MIPS/IRAC observations with BVRIJHK ancillary data in the Lockman Hole also shows very clear cases of galaxies with photometric redshifts at 1 ≲ z ≲ 2.5. The observed 24 μm fluxes indicate infrared luminosities greater than 10¹¹ L_⊙, while the data at shorter wavelengths reveal rather red and probably massive (M ≳ M*) galaxy counterparts. It is the first time that this population of luminous objects is detected up to z ∼ 2.5 in the infrared. Our work demonstrates the ability of the MIPS instrument to probe the dusty universe at very high red shift and illustrates how the forthcoming Spitzer deep surveys will offer a unique opportunity to illuminate a dark side of cosmic history not explored by previous infrared experiments.