## 4. Concluding remarksThe size limits given in this work illustrate the precision which can nowadays be reached in TeV gamma-ray astrophysics; a number of potential galactic and extragalatic sources are predicted to be extended sources on this scale. A few remarks concerning the interpretation of the limits: the
values quoted above refer to the rms source size, with the implicit
assumption that source strength is distributed over an area which is
similar to, or small compared to the angular resolution of the
instrument, such that the convolution of the source distribution and
the Gaussian response function can again be approximated by a Gaussian
distribution. This is obviously the case for a roughly Gaussian
source, and was explicitly checked for two alternative distributions,
namely (a) the case that the source strength is uniformly distributed
over the surface of a sphere of radius The limit on the size of the TeV emission region of the Crab Nebula is, by a factor around 4, larger than the size predicted by the standard inverse Compton models for gamma-ray production in the nebula. The limits, however, approach the sizes expected for hadronic production models, where high-energy gamma-rays are produced by nucleon interactions, more or less uniformly throughout the nebula. © European Southern Observatory (ESO) 2000 Online publication: October 10, 2000 |