Radio–X-ray constraints on jet collimation and spectral aging in the M87 jet

Abstract

We present a joint radio and X-ray study of the M87 jet aimed at examining the relationship between jet collimation and spectral evolution. Using multi-frequency Very Large Array (VLA) radio observations together with spatially resolved Chandra X-ray data, we analyze the large-scale jet morphology and the variation of the X-ray spectral index as a function of projected distance from the nucleus. The radio images reveal a systematic change in the jet collimation profile, while the X-ray analysis indicates progressive spectral steepening along the jet, consistent with radiative energy losses of the emitting particle population. The spatial correspondence between changes in jet structure and spectral behavior suggests that plasma processes, including hydrodynamic or current-driven instabilities, may contribute to energy dissipation along the jet. These results highlight the importance of combined radio and X-ray diagnostics for understanding jet dynamics and particle acceleration in active galactic nuclei.