A photometric analysis of the jet in Messier 87

Abstract

Results are presented for a detailed photometric analysis of the jet in M87. It is found that, contrary to previous conclusions, the individual knots are not stellar but are barely resolved with effective diameters proportional to the distance to the central source (the nonthermal component of the apparent nucleus). No continuous component could be detected, nor could any counterjet at the same level of sensitivity. The results show that if the expansion velocity is indicated by the half-width of the 3727-A forbidden O II emission line in the nucleus (i.e., 600 km/s), ejection velocities of the order of c/2 are suggested by the relativistic model of Shklovskii (1977), but the implied inclination of the jet to the line of sight (psi, approximately 6 deg) appears improbably small. The proper motions of the main knots are expected to be of the order of 0.05 arcsec per century for a range of plausible values of psi and v/c.