Superluminal Radio Features in the M87 Jet and the Site of Flaring TeV Gamma-Ray Emission

Superluminal motion is a common feature of radio jets in powerful γ-ray-emitting active galactic nuclei. Conventionally, the variable emission is assumed to originate near the central supermassive black hole where the jet is launched on parsec scales or smaller. Here we report the discovery of superluminal radio features within a distinct flaring X-ray-emitting region in the jet of the nearby radio galaxy M87 with the Very Long Baseline Array. This shows that these two phenomenological hallmarks—superluminal motion and high-energy variability—are associated, and we place this activity much farther (≥120 pc) from the "central engine" in M87 than previously thought in relativistic jet sources. We argue that the recent excess very high energy TeV emission from M87 reported by the H.E.S.S. experiment originates from this variable superluminal structure, thus providing crucial insight into the production region of γ-ray emission in more distant blazars.

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