The nonthermal characteristics of starburst galaxies and galaxy clusters are
reviewed and the perspectives for their observation in high energy gamma rays
discussed. It is argued that starburst galaxies should have physically similar
and even simpler nonthermal properties as our Galaxy, the particle transport
being convective in their strong galactic winds. They should be measurable in
TeV gamma rays by large detectors, and in fact the recent detection of NGC 253
is a first demonstration. Galaxy clusters are equally expected to produce a
nonthermal energetic nuclear particle component that gives unambiguous
information about the entropy production history in clusters. Both types of
objects should be main sources of and at the same time also major visible
representatives for the ubiquitous nonthermal component of matter in the
Universe.Comment: 14 pages, 5 figures: Invited paper presented at "The Universe Viewed
in Gamma-Rays" held on 25-28 Sept. 2002 in Kashiwa Japan. See
http://icrhp9.icrr.u-tokyo.ac.jp/Symp2002.htm
