FROM GALACTIC TO EXTRAGALACTIC JETS: A REVIEW
AbstractAn analysis of the data that have recently become available from observing campaigns, including VLA, VLBA, and satellite instruments, shows some remarkable similarities and significant differences in the data from some epochs of galactic microquasars, including GRS 1915+105, the concurrent radio and X-ray data  on Centaurus A (NGC 5128), 3C120 , and 3C454.3 as reported by Bonning et al. , which showed the first results from the Fermi Space Telescope for the concurrent variability at optical, UV, IR, and g-ray variability of that source. In combination with observations from microquasars and quasars from the MOJAVE Collaboration , these data provide time-dependent evolutions of radio data at mas (i.e., parsec for AGNs, and Astronomical Unit scales for microquasars). These sources all show a remarkable richness of patterns of variability for astrophysical jets across the entire electromagnetic spectrum. It is likely that these patterns of variability arise from the complex structures through which the jets propagate, but it is also possible that the jets constitution, initial energy, and collimation have significant observational consequences. On the other hand, Ulrich et al.  suggest that this picture is complicated for radio-quiet AGN by the presence of significant emission from accretion disks in those sources. Consistent with the jet-ambient-medium hypothesis, the observed concurrent radio and X-ray variability of Centaurus A  could have been caused by the launch of a jet element from Cen A’s central source and that jet’s interaction with the interstellar medium in the core region of that galaxy.
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