3. SEARCHING FOR CLUES

Data were obtained for a limited sample of BLRGs with ISOPHOT on board ISO (Lemke et al. 1996, Kessler et al. 1996), in the bands 12, 25, 60, 90 and 160 µm, using the P1, P2, C1 and C2 detectors. The observations were made in raster mode, to avoid the known problems with chopping, which are especially serious for these faint sources. The reduction of the C1 and C2 data is described in van Bemmel et al. (2000), and the reduction of the P1 and P2 data will be described in a future paper (van Bemmel et al. 2001). From additional ISOPHOT and literature data, two samples were selected, one of 25 µm peakers and one of normal NLRGs and BLRGs. Due to the limited amount of infrared data, the comparison sample consists largely of NLRGs.

Data in other spectral regimes were extracted from the NASA/IPAC Extragalactic Database (NED) and the literature. The exact references for all data will also be given in the future paper (van Bemmel et al. 2001). The two samples are listed in Table 1, which gives their classification, infrared powers at 25 and 60 µm and radio power at 178 MHz.