A DETAILED INVESTIGATION OF PROJECTION EFFECTS RELEVANT TO THE STUDY OF POWERFUL CLASSICAL DOUBLE RADIO SOURCES

A detailed investigation of projection e†ects involved in the study of classical double sources is pre-sented here. Theoretical calculations of the way projection e†ects enter empirically determined param-eters are studied. It is shown that some parameters, such as the lobe width, are rather insensitive to the projection angle, while other parameters, such as the ambient gas density, are more sensitive. The deviation of the observed value from the true value of any given parameter is usually not signiÐ-cant when the projection angle is greater than about 60 ¡ and is signiÐcant only at very small projection angle, at which the symmetry axis of the source is pointing close to the line of sight to the observer. Applications of the theoretical model to a sample of classical double radio sources yield the following principal results: 1. A comparison between the radio-loud quasars and the radio galaxies in the sample suggests that their average projection angles are very similar. The average projection angle of the radio-loud quasars in the sample is greater than 35¡È40 ¡ at the 3 p level, assuming that the average projection angle of radio galaxies is 70 ¡ or above. 2. On average, the low-redshift radio-loud quasars in the sample have much lower lobe surface bright