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Session 66 - Radio - Loud AGN & Extragalactic Jets.
Oral session, Thursday, January 08

[66.02] Detailed Studies of Radio Power Selection Effects, Projections Effects, and Redshift Evolution of Key Parameters of Classical Double Radio Sources

L. Wan (Princeton U.)

A sample of about 20 classical double radio sources with redshifts between zero and two was compiled to study the properties of powerful FRII sources and their gaseous environments.

A detailed investigation of radio power selection effects suggests that these selection effects are unlikely to be significant for most of the derived parameters, such as the ambient gas density and characteristic size of a source. Projection effects are also studied in detail. It is found that projection effects typically do not have a significant impact on derived properties for sources with projection angles greater than about 60^\circ, measured with respect to the line of sight to the observer. At small projection angle, parameters such as the ambient gas density and the luminosity in directed kinetic energy of the jet (i.e. the beam power) are sensitive to projection effects, while parameters such as the lobe width and the radio spectral index are rather insensitive. Comparisons between radio galaxies and radio loud quasars suggest that the average projection angle of the radio loud quasars in the sample studied is likely to be greater than about 35^\circ to 40^\circ. A careful study of Cygnus A suggests that its projection angle is probably greater than about 40^\circ to 55^\circ, consistent with independent estimates. The data also suggest that the low-redshift radio loud quasars in the sample have lower radio surface brightness and lower non-thermal pressure than radio galaxies; the difference is so large, it can not be explained by projection effects.

The beam power, the density, temperature and thermal pressure of the ambient gas, and the gravitational mass of the surrounding cluster are also estimated for each source in the sample. The redshift evolution of these parameters are discussed. One interesting result is that, for radio loud quasars, the beam power is strongly correlated with the optical luminosity of the quasar.

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Program listing for Thursday