2007ApJ...659..305H

We present 70 µm properties of submillimeter galaxies (SMGs) in the Great Observatories Origins Deep Survey (GOODS) North field. Out of 30 submillimeter galaxies (S₈₅₀>2 mJy) in the central GOODS-N region, we find two with secure 70 µm detections. These are the first 70 µm detections of SMGs. One of the matched SMGs is at z∼0.5, and has S₇₀/S₈₅₀and S₇₀/S₂₄ratios consistent with a cool galaxy. The second SMG (z=1.2) has infrared-submillimeter colors that indicate it is more actively forming stars. We examine the average 70 µm properties of the SMGs by performing a stacking analysis, which also allows us to estimate that S₈₅₀>2 mJy SMGs contribute 9%±3% of the 70 µm background light. The S₈₅₀/S₇₀colors of the SMG population as a whole is best fit by cool galaxies, and because of the redshifting effects these constraints are mainly on the lower z subsample. We fit spectral energy distributions (SEDs) to the far-infrared data points of the two detected SMGs and the average low-redshift SMG (z_median=1.4). We find that the average low-z SMG has a cooler dust temperature than local ultraluminous infrared galaxies (ULIRGs) of similar luminosity and an SED that is best fit by scaled-up versions of normal spiral galaxies. The average low-z SMG is found to have a typical dust temperature T=21-33 K and infrared luminosity L_8–1000µm=8.0x10¹¹ L_☉. We estimate the AGN contribution to the total infrared luminosity of low-z SMGs is less than 23%.