CCD photometry of the M87 jet

CCD photometry of the M87 jet in the Thuan-Gunn r and g filters is presented. Accurate elliptical models of the underlying stellar emission were subtracted from the reduced and calibrated frames. The residual images show a number of morphological features not clearly seen before such as the faint extension at the end of the jet and faint red diffuse emission parallel to the jet on its northern side. The optical spectrum of the knots between the r and g bands is steeper than in the radio and, in general, becomes steeper with distance from the nucleus. The implications of this new result for particle acceleration mechanisms in jets are briefly discussed. The nondetection of a counterjet at an intensity level 300 times fainter than the jet places stronger constraints to relativistic beaming models of M87. 30 references.