I present a brief overview of observational, modeling and theoretical issues related to ageing calculations based on spectral steepening. These include problems such as inhomogeneous magnetic fields, diffusion of relativistic particles, confusion from multiple particle populations and particle acceleration. Although some of the effects are only of order unity, others call into question the entire ageing paradigm. I refer to and show some data illustrating these problems and make a few recommendations about how we should proceed given these uncertainties.
Bibliographical noteFunding Information:
This work is supported by NSF grant AST 96-16964. I am grateful for many stimulating conversations with T. Delaney, J. Eilek, M. Hardcastle, T. Jones, D. Katz-Stone, B. Koralesky, J.P. Leahy, I. Tregillis, A. Young and others who wish to protect their reputations by remaining anonymous.
- Acceleration of particles
- Galaxies: Evolution, magnetic fields
- Radiation mechanisms: Non-thermal
- Radio continuum: Galaxies