New observational constraints on the M87 jet

New observations at 1.6-3.45 mu m confirm the presence of a dramatic (Delta alpha similar to 1) break between radio-IR wavelengths and 6,000 angstrom, in the spectrum of the M87 jet. These data, in combination with data taken in other spectral regions, show that the individual knots in the M87 jet have nearly the same spectral indices and nearly the same large (Delta alpha similar to 1) spectral break. This large spectral break and the constancy of spectral properties between the knots pose serious constraints for models of the M87 jet.