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We present the far-IR, millimeter, and radio photometry as well as opticaland near-IR spectroscopy of a sample of 48 z~1-3 Spitzer-selected ULIRGs withIRS mid-IR spectra. Our goals are to compute their bolometric emission, and todetermine both the presence and relative strength of their AGN and starburstcomponents. We find that strong-PAH sources tend to have higher 160um and 1.2mmfluxes than weak-PAH sources. The depth of the 9.7um silicate feature does notaffect MAMBO detectability. We fit the far-IR SEDs of our sample and find anaverage <L_{IR}>~7x10^{12}Lsun for our z>1.5 sources. Spectral decompositionsuggests that strong-PAH sources typically have ~20-30% AGN fractions. Weak-PAHsources by contrast tend to have >~70% AGN fractions, with a few sources havingcomparable contributions of AGN and starbursts. The optical line diagnosticssupport the presence of AGN in the bulk of the weak-PAH sources. With oneexception, our sources are narrow-line sources, show no obvious correspondencebetween the optical extinction and the silicate feature depth, and, in twocases, show evidence for outflows. Radio AGN are present in both strong-PAH andweak-PAH sources. This is supported by our sample's far-IR-to-radio ratios (q)being consistently below the average value of 2.34 for local star-forminggalaxies. We use survival analysis to include the lower-limits given by theradio-undetected sources, arriving at <q>=2.07+/-0.01 for our z>1.5 sample. Intotal, radio and, where available, optical line diagnostics support thepresence of AGN in 57% of the z>1.5 sources, independent of IR-baseddiagnostics. For higher-z sources, the AGN luminosities alone are estimated tobe >10^{12}Lsun, which, supported by the [OIII] luminosities, implies that thebulk of our sources host obscured quasars.

Spitzer Mid-Infrared Spectroscopy of Infrared Luminous Galaxies at z~2 III: Far-IR to Radio Properties and Optical Spectral Diagnostics