A FIRST GLIMPSE INTO THE FAR-IR PROPERTIES OF HIGH-z UV-SELECTED GALAXIES: HERSCHEL/PACS OBSERVATIONS OF z ∼ 3 LBGS

We present first insights into the far-IR properties for a sample of IRAC and MIPS 24 mu m detected Lyman break galaxies (LBGs) at z similar to 3, as derived from observations in the northern field of the Great Observatories Origins Survey (GOODS-N) carried out with the PACS instrument on board the Herschel Space Observatory. Although none of our galaxies are detected by Herschel, we employ a stacking technique to construct, for the first time, the average spectral energy distribution (SED) of infrared luminous LBGs from UV to radio wavelengths. We derive a median IR luminosity of L-IR = 1.6 x 10(12) L-circle dot, placing the population in the class of ultra-luminous infrared galaxies (ULIRGs). Complementing our study with existing multi-wavelength data, we put constraints on the dust temperature of the population and find that for their L-IR, MIPS-LBGs are warmer than submillimeter-luminous galaxies while they fall in the locus of the L-IR-T-d relation of the local ULIRGs. This, along with estimates based on the average SED, explains the marginal detection of LBGs in current submillimeter surveys and suggests that these latter studies introduce a bias toward the detection of colder ULIRGs in the high-z universe, while missing high-z ULIRGS with warmer dust.