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The first hard X-ray spectrum of a kpc-scale jet with NuSTAR

Presentation #100.95 in the session AGN.

Published onJul 01, 2023
The first hard X-ray spectrum of a kpc-scale jet with NuSTAR

High-resolution imaging with Chandra and HST has revealed that many powerful jets emit strongly in the optical/UV and X-rays on kpc to Mpc scales. In the most powerful jets, the optical and X-ray have spectral properties which show they are not a continuation of the radio synchrotron emission. These extra high-energy emission components, despite dominating the energetic output, are currently unidentified. Understanding the emission mechanism in jets is the only way to get a proper accounting of the energy they carry and the impact on their environments. We present a deep (400 ks) NuSTAR observation of Pictor A, the only large-scale resolved jet target which can be easily resolved and detected separately from the AGN core. We find that the X-ray spectrum continues into the NuSTAR band with virtually the same spectral index as that seen in deep Chandra observations, with no evidence of a cut-off. We confirm strong variability in the hotspot as seen by Chandra, and some hints of the same in the NuSTAR observations. We interpret the full suite of observations as indicating a synchrotron origin for the X-ray emission, from a distinct electron energy distribution from that which produces the radio emission.

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