We have combined high resolution VLBI Space Observatory Programme (VSOP) data
at 1.6 and 4.8 GHz with Very Long Baseline Array (VLBA) data at higher
frequencies and with similar resolutions to study the spectral properties of
the core of M87 with milliarcsecond resolution. The VSOP data allow a more
accurate measurement of the turn-over frequency, and hence more reliable
determination of associated physical parameters of the source. Comparison of
the images with previously published images yields no evidence for significant
motion of components in the parsec-scale jet. In addition, the brightness
temperatures obtained from model-fits to the core are well below the inverse
Compton limit, suggesting the radio emission we are observing is not strongly
Doppler boosted.
Colour version on http://www.vsop.isas.jaxa.jp/survey/publications/m87.ps.gzComment: To appear in PASJ VSOP special issue. Minor correction