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Description
Extragalactic sources detected at lambda=60um were selected from the IRAS Faint Source Catalog, Version 2 (Cat. II/156) by the criterion S(60um)>=S(12um). They were identified by position coincidence with radio sources stronger than 25mJy at 4.85GHz in the 6.0sr declination band 0deg<Dec.<+75deg (excluding the 0.05sr region 12h40m<R.A.<14h40m, 0deg<Dec.<+5deg) and with radio sources stronger than 80mJy in the 3.4sr area 0h<R.A.<20h, -40deg<Dec.<0deg (plus the region 12h40m<R.A.<14h40m, 0deg<Dec.<+5deg). Fields containing new candidate identifications were mapped by the VLA at 4.86GHz with about 15" FWHM resolution. Difficult cases were confirmed or rejected with the aid of accurate (sigma~1") radio and optical positions. The final sample of 354 identifications in Omega=9.4sr is reliable and large enough to contain statistically useful numbers of radio-loud FIR galaxies and quasars. The logarithmic FIR/radio flux ratio parameter q can be used to distinguish radio sources powered by "starbursts" from those powered by "monsters." Starbursts and normal spiral galaxies in a lambda=60um flux-limited sample have a narrow (sigma_q=0.14+/-0.01) q distribution with mean <q>=2.74+/-0.01, and none have "warm" FIR spectra [{alpha}(25um, 60um)<1.5]. The absence of radio-quiet (but not completely silent) blazars indicates that nearly all blazars become optically thin at frequencies {nu}<~100GHz. Nonthermal sources with steep FIR/optical spectra and dust-embedded sources visible only at FIR and radio wavelengths must be very rare.
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