HerMES: Spectral Energy Distributions of Submillimeter Galaxies at z > 4
Bock, J. J.; Clements, D. L.; Burgarella, D.; Wang, L.; Cooray, A.; Farrah, D.; Rigopoulou, D.; Symeonidis, M.; Fazio, G. G.; Huang, J. -S.; Chapman, S.; Glenn, J.; Magdis, G.; Rowan-Robinson, M.; Smith, A. J.; Riechers, D.; Efstathiou, A.; Oliver, S.; Roseboom, I.; Dai, Y.; Page, M.; Webb, T. M. A.; Yun, M.
China, Chile, United States, United Kingdom, France, Canada, Cyprus
Abstract
We present a study of the infrared properties for a sample of seven spectroscopically confirmed submillimeter galaxies (SMGs) at z > 4.0. By combining ground-based near-infrared, Spitzer IRAC and MIPS, Herschel SPIRE, and ground-based submillimeter/millimeter photometry, we construct their spectral energy distributions (SEDs) and a composite model to fit the SEDs. The model includes a stellar emission component at λrest < 3.5 μm, a hot dust component peaking at λrest ~ 5 μm, and cold dust component which becomes significant for λrest > 50 μm. Six objects in the sample are detected at 250 and 350 μm. The dust temperatures for the sources in this sample are in the range of 40-80 K, and their L FIR ~ 1013 L ⊙ qualifies them as hyper-luminous infrared galaxies. The mean FIR-radio index for this sample is around langqrang = 2.2 indicating no radio excess in their radio emission. Most sources in the sample have 24 μm detections corresponding to a rest-frame 4.5 μm luminosity of Log10(L 4.5/L ⊙) = 11 ~ 11.5. Their L 4.5/L FIR ratios are very similar to those of starburst-dominated SMGs at z ~ 2. The L CO - L FIR relation for this sample is consistent with that determined for local ULIRGs and SMGs at z ~ 2. We conclude that SMGs at z > 4 are hotter and more luminous in the FIR but otherwise very similar to those at z ~ 2. None of these sources show any sign of the strong QSO phase being triggered.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.