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Enhanced X-ray Emission from the Most Radio-Powerful Quasar in the Universe's First Billion Years

, , , , , , , , , , and . (2021)cite arxiv:2103.03879Comment: 16 pages, 7 Figures. Accepted for publication the Astrophysical Journal.

Abstract

We present deep (265 ks) Chandra X-ray observations of PSO J352.4034$-$15.3373, a quasar at z=5.831 that, with a radio-to-optical flux ratio of R>1000, is one of the radio-loudest quasars in the early universe and is the only quasar with observed extended radio jets of kpc-scale at $z \gtrsim 6$. Modeling the X-ray spectrum of the quasar with a power law, we find a best fit of $\Gamma = 1.99^+0.29_-0.28$, leading to an X-ray luminosity of $L_2-10 = 1.26^+0.45_-0.33 10^45\ erg\ s^-1$ and an X-ray to UV brightness ratio of $\alpha_OX = -1.36 0.11$. We identify a diffuse structure 50 kpc ($\sim8^\prime\prime$) to the NW of the quasar along the jet axis that corresponds to a $3\sigma$ enhancement in the angular density of emission and can be ruled out as a background fluctuation with a probability of P=0.9985. While with few detected photons the spectral fit of the structure is uncertain, we find that it has a luminosity of $L_2-10\sim10^44\ erg\ s^-1$. These observations therefore potentially represent the most distant quasar jet yet seen in X-rays. We find no evidence for excess X-ray emission where the previously-reported radio jets are seen (which have an overall linear extent of $0.^\prime\prime28$), and a bright X-ray point source located along the jet axis to the SE is revealed by optical and NIR imaging to not be associated with the quasar.

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Enhanced X-ray Emission from the Most Radio-Powerful Quasar in the Universe's First Billion Years

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