Implications of the synchrotron emission in plerionic nebulae: a second component in the Crab Nebula
Abstract
Description
High-quality spatially resolved spectra of synchrotron emission from plerions represent a powerful diagnostic tool for the physical conditions in these objects. A fundamental question is to what extent spatial variations of the synchrotron spectrum originate from the evolution of a single population of injected electrons, and when instead they imply the coexistence of different populations of electrons. Here I shall discuss observations of the Crab Nebula at millimetric wavelengths which, compared with a radio map, show evidence for the emergence of a second synchrotron component, characterized by a flatter spectrum and undetected in the radio range. This component is confined to the inner part of the nebula, and cannot originate from synchrotron-dominated evolution, also because in the Crab Nebula the electrons emitting at millimeter wavelengths evolve almost adiabatically. Then its discovery indicates that there are more populations of injected particles. Finally, the detection of a low-frequency break in the spectra of synchrotron filaments can be interpreted as an effect of higher magnetic fields in filaments.
4 pages, Latex, 2 figures, Encapsulated PostScript "To appear in "Neutron Stars in Supernova Remnants" (ASP Conference Proceedings), eds P. O. Slane and B. M. Gaensler"
4 pages, Latex, 2 figures, Encapsulated PostScript "To appear in "Neutron Stars in Supernova Remnants" (ASP Conference Proceedings), eds P. O. Slane and B. M. Gaensler"