We present a study of the infrared properties for a sample of seven spectroscopically confirmed submillimeter galaxies 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 ( SED ) and a composite model to fit the SEDs .
The model includes a stellar emission component at \lambda _ { rest } < 3.5 \mu m ; a hot dust component peaking at \lambda _ { rest } \sim 5 \mu m ; and cold dust component which becomes significant for \lambda _ { rest } > 50 \mu m. Six objects in the sample are detected at 250 and 350 \mu m. The dust temperatures for the sources in this sample are in the range of 40 - 80 K , and their L _ { FIR } \sim 10 ^ { 13 } L _ { \odot } qualifies them as Hyper - Luminous Infrared Galaxies ( HyperLIRGs ) .
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 \mu m detections corresponding to a rest-frame 4.5 \mu m luminosity of Log _ { 10 } ( L _ { 4.5 } /L _ { \odot } ) = 11 \sim 11.5 .
Their L _ { 4.5 } / L _ { FIR } ratios are very similar to those of starburst dominated submillimeter galaxies at z \sim 2 .
The L _ { CO } - L _ { FIR } relation for this sample is consistent with that determined for local ULIRGs and SMGs at z \sim 2 .
We conclude that submillimeter galaxies at z > 4 are hotter and more luminous in the FIR , but otherwise very similar to those at z \sim 2 .
None of these sources show any sign of the strong QSO phase being triggered .