Annu. Rev. Astron. Astrophys. 1980. 18: 165-218
Copyright © 1980 by . All rights reserved

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5. RADIO-SOURCE STRUCTURE AND THE ENVIRONMENT

But it is an error to suppose, because we resolve to confine our attention to a certain number of the properties of an object that we therefore conceive, or have an idea of, the object denuded of its other properties.

J.S. Mill, Logics and Mathematics Based on Observation

5.1. Characteristic Scales

Some typical scales observed in extended radio sources and their environment are compared in Table 2. Note the similarities between the characteristic radio and optical scales. These suggest that the radio-source phenomenon may be intimately connected with properties of the source environment. Here we shall consider possible relationships.

Table 2. Some characteristic scales observed in extended radio sources

Length (pc) Radio Optical

~ 10-3   Nuclear nonthermal continuum
~ 10-1 Flat-spectrum core Broad (permitted) line region
~ 103 Steep-spectrum core Narrow (forbidden) line region
~ 104.5   Galaxy
~ 105.2 Extended radio source Galactic halo

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