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Published February 6, 2012 | public
Book Section - Chapter

Observational Details: Radio


In this chapter we discuss the observations of radio jets. After some introductory remarks, mainly describing the classic Fanaroff–Riley separation of double radio sources, we separate the topic into small-scale (parsec) and large-scale (kiloparsec) jets. These two types of objects have been studied with different telescopes and the two subfields have developed largely independently of each other. Very Long Baseline Interferometry (VLBI) with angular resolution of 1 milliarcsecond (mas) and better is used at parsec (pc) scales, and the Very Large Array (VLA) and similar instruments are used for larger scales. VLBI is sensitive only to high surface-brightness features (≳ 10^5 K) and so typically studies only the core region of a source; whereas the VLA can image the faint outer plumes of a radio galaxy but its core region is subsumed into an unresolved bright spot. This instrumental distinction, however is not definitive, as some observations at certain frequencies cover the intermediate range, e.g., MERLIN and its connections to the European VLBI Network cover a wide range of scales. See Figure 1.1 for a montage of VLBI and VLA images that span the pc–kpc range.

Additional Information

© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA. Published Online: 06 February 2012; Published Print: 11 January 2012. AHB thanks Robert Laing for many stimulating discussions and insights about observations of radio jets and their interpretation. MHC thanks Matt Lister and Ken Kellermann for helpful comments on the manuscript.

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