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6.1.2 Observed LFs of High-Luminosity Radio Sources

Given the 2 Jy sample as defined, we calculate the luminosity functions of high-power radio sources as follows. First, we fit an exponential pure luminosity evolution model to each sample, by finding the evolutionary parameter which makes < V / Vmax > = 0.5 and then testing the goodness of fit via a KS test. The best-fit values of tau for each sample are listed in Table 2, along with median redshifts and < V / Vmax > values. Each luminosity function was de-evolved using the appropriate best-fit evolution. Figure 14 shows the resulting local luminosity functions at 2.7 GHz for FR IIs, SSRQ, and FSRQ. (14)

Table 2. Evolution of AGN Samples

Table 2

The luminosity function of FSRQ LF (filled circles) is flattest and extends to the highest luminosities. The luminosity functions of SSRQ (open triangles; Fig. 14) and FR II galaxies (open squares) are similar in shape over the common range of powers, but the SSRQ are lower in number density: the number ratio of the two classes for P2.7 gtapprox 5 x 1025 W Hz-1 is 6.4. This is larger than in Padovani and Urry (1992), due to the different LF used for the FR II galaxies.

Figure 14
Figure 14. Local differential radio luminosity functions for high-luminosity radio sources: flat spectrum radio quasars (filled circles), steep spectrum radio quasars (open triangles), and FR II galaxies (open squares). The error bars represent the sum in quadrature of the 1 sigma Poisson errors (Gehrels 1986) and the variations of the number density associated with a 1 sigma change in the evolutionary parameter tau (see Padovani and Urry 1992 for details). The luminosity functions of FR IIs and SSRQ have similar slopes and extend to the same luminosity at the bright end, although the FR IIs extend a decade lower at the faint end. The FSRQ luminosity function is distinctly flatter and extends to higher luminosities. This agrees well with the predictions of a beaming model calculated for FSRQ (solid line) and SSRQ (dot-dashed line); see Sec. 6.1.3 (Table 3) for details of the model parameters.

14 The FSRQ luminosity function includes PKS 0521-365, which was inadvertently excluded by Padovani and Urry (1992). This is a low redshift, highly polarized object (Angel and Stockman 1980), classified as a galaxy by Wall and Peacock (1985) and as a BL Lac by Véron-Cetty and Véron (1993) but showing broad Balmer lines (see Sec. 7.2). It was not included in the 1 Jy BL Lac sample (Stickel et al. 1991) because two emission lines exceeded the equivalent width criterion, but its [O III] luminosity is more typical of BL Lacs than of FSRQ, so it could be a transitional object (see Sec. 7.1). Back.

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