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5.3 Isotropic Properties of Quasars and FR~II Galaxies

5.3.1 Extended Radio Emission

FR II radio galaxies are dominated by emission from large, diffuse radio lobes which is almost certainly unbeamed, especially at low frequencies where the contribution from flat-spectrum hot spots is minimal. The radio luminosities of the extended structures of FR II galaxies and quasars should therefore be comparable if the unified scheme is right. The fact that most compact radio sources have substantial extended radio power has been known for more than a decade (Ulvestad et al. 1981) and the distributions of Pext for compact radio sources (largely quasars) and 3CR/B2 radio galaxies (at 1.5 GHz) do overlap (Antonucci and Ulvestad 1985).

Figure 6. A comparison of the extended radio powers at 5 GHz for FR II radio galaxies (dashed line), steep-spectrum radio quasars (dot-dashed line), and flat-spectrum radio quasars (solid line) from the 2 Jy sample (Wall and Peacock 1985; di Serego Alighieri et al. 1994a, b). Data for the FR IIs come from Morganti et al. (1993), those for FSRQ have been derived from the R values (Appendix C) given by Padovani (1992b), updated with lower limits from Ulvestad et al. (1981), while extended radio powers for SSRQ have been collected from the literature (mostly from Browne and Murphy 1987). Upper limits on extended power for FSRQ are indicated with the symbol ``<''. Radio powers have been de-evolved using the best-fit evolution for each class (Table 2).

In terms of the quasar - FR II unification scheme in particular, the extended radio luminosities at a few GHz of complete samples of FSRQ and SSRQ are typical of those for complete samples of FR II radio galaxies, as shown in Fig. 6 for the 2 Jy sample. (All radio powers have been de-evolved using the best-fit evolution appropriate for that class; see Sec. 6.1) We note that it is not appropriate to use the Kolmogorov-Smirnov (KS) statistic to test whether these distributions are compatible - or similarly, whether the distributions of redshift or narrow-line luminosity are comparable for blazars and radio galaxies - because the sample identification itself involves strong selection effects from relativistic beaming and thus one should not expect the shape of the distributions to be the same. For example, since beamed objects can be detected to higher redshifts, in a flux-limited sample they will be intrinsically more luminous as well. The histograms in Fig. 6 demonstrate only that the range in unbeamed radio luminosity overlaps completely, not that the distributions have the same shape.

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