Figure 3 shows two radio-optical planes for Class A and Class B objects in an example grand unification scheme (after Meier 1999). These figures are to be compared with observed radio-optical planes like that of Ledlow & Owen (1996). As the optical luminosity of the galaxy or quasar scales with black hole mass in both cases, the horizontal axis is MH in both. The vertical axis is the observed radio power using the Bicknell factor to convert Ljet to Prad. The curves separate the plane into several different black hole spin states: NO sources (j > 1 is not allowed); FR II sources (jcrit < j < 1), FR I sources (jmin < j < jcrit), and radio quiet objects (j < jmin). For jcrit we have used here the generalized magnetic switch of Meier (1999), but Bicknell's FR I/II transonic condition could be substituted. For jmin we have chosen the point where the predicted black hole MHD power in equation (5) equals the thin disk MHD power with Bp = (H/R) B. Other observational definitions of radio quietness (using the radio-optical flux ratio) are shown.
Figure 3. Example of a grand unification scheme (after Meier 1999). Left panel shows Class B objects (e.g., radio galaxies; = 0.01), right panel Class A objects (e.g., quasars; = 0.1). Lines dividing the radio-optical planes are discussed in the text.
This grand unification scheme makes some interesting predictions. There should be a population of sources corresponding to FR I quasars (high , low j). These were formerly FR II sources, but their holes have since spun down. However, the spindown time for Class A sources is so short (equation 7) that it is likely that the FR II hot spots will still be radiating as the source goes through the FR I phase. Such hybrid FR II sources could be identified by young diffuse emission or ``bridges'' between the radio core and the hot spots. The FR IIa quasars identified by R. Daly (these proceedings) are candidates for such sources; the FR IIa/IIb transition also appears to occur near the j = jcrit line in Figure 3b.
There also should be a population of high redshift, faint sub-mJy FR I and II radio sources associated with spiral galaxies or pre-spiral bulges (MH < 107 M). If the accretion rate was high at that time - the most likely case in the early universe - then these may appear as optically faint radio quasars (Lopt 1043 erg s-1, Prad 1023-27 W Hz-1). Their numbers should be a significant fraction of the present-day spiral population, exceeding the contribution of quasars residing in elliptical galaxies alone.