2014ApJ...784...52H

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 λ_rest< 3.5 µm, a hot dust component peaking at λ_rest∼ 5 µm, and cold dust component which becomes significant for λ_rest> 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 < q > = 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_FIRrelation 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.