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Paper: Extragalactic Jets: Some Unanswered Questions and the Prospects for GLAST
Volume: 386, Extragalactic Jets: Theory and Observation from Radio to Gamma Ray
Page: 3
Authors: Blandford, R.
Abstract: An introduction to AGN jets is presented, paying particular attention to general questions that are currently being addressed or are likely to be addressed using imminent observational capabilities in the gamma ray and radio bands. It is argued that it should become possible to locate the sites of radio and gamma ray emission and to define the jet kinematical structure in a far more prescriptive fashion. Astrophysical arguments should then suffice to affirm (or refute) the common presumptions that synchrotron and inverse Compton emission dominate other processes and that the working substance changes from electromagnetic field to a pair plasma to an ionic plasma as the jet propagates away from the central black hole. Our understanding of jet dynamics can also improve through better characterization of the properties of the surrounding medium which should help decide if magnetic pinching is important and lead to more accurate measurements of jet powers, thrusts, discharges and currents. Combining jet and disk observations should test a “Central Dogma”, namely that intrinsic AGN behavior is mainly dictated by the mass supply rate in units of the Eddington rate and the spin of the hole in units of its maximum allowed value, with the overall scale of power, variation etc determined by the hole mass. The connection between observed jet properties and the physical processes occurring around black holes is likely to remain conjectural for a while, though relevant numerical simulations are improving rapidly. Finally, the environmental impact of jets should become much clearer along with the role of AGN in the co-evolution of their host galaxies.
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