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

First Hard X-Ray Observation of a Compact Symmetric Object: A Broadband X-Ray Study of a Radio Galaxy OQ+208 with NuSTAR and ChandraSobolewska, MałgosiaSiemiginowska, AnetaGuainazzi, MatteoHardcastle, MartinMigliori, GiuliaOstorero, LuisaStawarz, ŁukaszDOI: info:10.3847/1538-4357/ab3ec3v. 884166
Sobolewska, Małgosia, Siemiginowska, Aneta, Guainazzi, Matteo, Hardcastle, Martin, Migliori, Giulia, Ostorero, Luisa, and Stawarz, Łukasz. 2019. "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." The Astrophysical Journal 884:166. https://doi.org/10.3847/1538-4357/ab3ec3
ID: 154719
Type: article
Authors: Sobolewska, Małgosia; Siemiginowska, Aneta; Guainazzi, Matteo; Hardcastle, Martin; Migliori, Giulia; Ostorero, Luisa; Stawarz, Łukasz
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 to 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 the Nuclear Spectroscopic Telescope Array (NuSTAR). Our target, OQ +208, is detected up to 30 keV, and thus we establish CSOs as a new class of the NuSTAR sources. We analyze the NuSTAR data jointly with our new Chandra and archival XMM-Newton data and find that a young (̃250 yr 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 of N H = 1023-1024 cm-2. The primary X-ray emission is characterized by a photon index of Γ ̃ 1.45 and an intrinsic 0.5-30 keV luminosity of L ≃ 1043 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 unobscured/X-ray-obscured active galactic nucleus. 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.