Authors:
Edwards, PG; Giovannini, G; Cotton, WD; Feretti, L; Fujisawa, K; Hirabayashi, H; Lara, L; Venturi, T
Journal:
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
Abstract:
One of the features of VSOP observations is the ability to make contemporaneous, matched-resolution images at different frequencies in order to produce spectral index maps. We have combined VSOP observations made at 4.8 GHz on 1998 April 7 and 1.6 GHz on 1998 April 8 to make such a map of the variable X-ray and TeV gamma-ray source Mkn 501. The spectral index map reveals considerably more information than a single frequency total intensity image, and shows significant spectral variation along and across the milli-arcsecond scale jet. We interpret this in terms of models for the jet involving an inner fast spine and slower outer shear layer.
Keywords:
BL Lacertae objects : individual (Markarian 501=1652+398); galaxies : active; radio continuum : galaxies; techniques : interferometric