The deepest X-ray view of a kiloparsec-scale jet at z=6.1

Context: The mechanism responsible for the high-energy emission observed in kiloparsec scale jets across cosmic time remains poorly understood. The relativistic jet associated with the z=6.1 AGN PSO J030947.49+271757.31 represents the highest z large-scale jet currently resolved in the X-rays and provides a unique laboratory to study the evolution of these structures. Aim: We present a study aimed at constraining the morphology and spectral properties of the kiloparsec-scale jet associated with PSO J030947.49+271757.31. In addition, we intend to investigate the capabilities of future X-ray observatories in the study of extended jets. Methods: We obtained new dedicated observations of PSO J030947.49+271757.31 with the Chandra X-ray Observatory (for a total of 360 ksec combined with archival data). Thanks to the improvement of a factor of sim3 in exposure time compared to previous studies, we spatially resolved the extended X-ray emission into two distinct components and performed spatially resolved spectral analyses of the different regions. Results: We confirmed the presence of extended X-ray emission of PSO J030947.49+271757.31 with significantly improved statistics and identified two separate and slightly resolved components. The X-ray spectrum of the extended emission has a photon index of Γ = 2.25^ +0.45 _ -0.44 , i.e., steeper than that of the core (Γ = 1.86 /L_ and an extended-to-core-luminosity ratio of L_ ̊m ext ̊m core =18%. Using the Chandra image as input, we performed simulations for next-generation X-ray facilities. An AXIS-like mission would increase the detected photon statistics by a factor of sim17 compared to the current Chandra dataset. Conclusions: We resolved the kiloparsec-scale jet associated with this z=6.1 AGN into two main components and constrained its spectral properties. This extended component corresponds to the most distant and one of the most X-ray-luminous large-scale jets currently known. Simulations show that future X-ray missions with arcsecond-scale angular resolution will not only enable significantly more detailed studies of systems such as PSO J030947.49+271757.31, it will also reveal a population of fainter high-redshift jets currently beyond the reach of Chandra .