First Hard X-ray Observation of a Compact Symmetric Object: A Broadband X-ray Study of a radio galaxy OQ+208 with NuSTAR and Chandra

Abstract

Compact Symmetric Objects (CSOs) have been observed with Chandra and XMM-Newton to gain insights into the initial stages of a radio source evolution and probe the black hole activity at the time of relativistic outflow formation. However, there have been no CSO observations to date at the hard X-ray energies (> 10 keV), impeding our ability to robustly constrain the properties of the intrinsic X-ray emission and of the medium surrounding the young expanding jets. We present the first hard X-ray observation of a CSO performed with NuSTAR. Our target, OQ+208, is detected up to 30 keV, and thus we establish CSOs as a new class of NuSTAR sources. We analyze the NuSTAR data jointly with our new Chandra and archival XMM-Newton data and find that a young, ~250 years old, radio jet spanning the length of ~10 pc coexists with cold obscuring matter, consistent with a dusty torus, with an equivalent hydrogen column density $N_H=10^{23}$-$10^{24}$ cm${}^{-2}$. The primary X-ray emission is characterized by a photon index $\Gamma \sim 1.45$ and intrinsic 0.5-30 keV luminosity $L\sim 10^{43}$ erg s${}^{-1}$. The results of our spectral modeling and broad-line optical classification of the source suggest a porous structure of the obscuring torus. Alternatively, the source may belong to the class of optically un-obscured/X-ray obscured AGN. The observed X-ray emission is too weak compared to that predicted by the expanding radio lobes model, leaving an accretion disk corona or jets as the possible origins of the X-ray emission from this young radio galaxy.

7 pages, 3 figures, ApJ, in press

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• The Origin of High Energy Emission in the Young Radio Source PKS 1718-649
• X-ray Emission of the $\gamma$-ray Loud Young Radio Galaxy NGC 3894
• Jetted subgalactic-size radio sources in merging galaxies -- A jet redirection scenario
• The Complex X-ray Obscuration Environment in the Radio Loud Type 2 Quasar 3C 223