The origin of X-ray emission in 3CRR sources: hints from mid-infrared Spitzer observations

Abstract

Whether X-ray emission in radio-loud (RL) active galactic nuclei (AGNs) originates from disk coronae or jets is still under debate. For example, the positive relationships in radio-quiet (RQ) AGNs (such as the optical to X-ray spectral index ${\alpha }_{\mathrm{OX}}$ and Eddington ration ${\lambda }_{\mathrm{O}}$ as well as the X-ray photon index $\Gamma$ and ${\lambda }_{\mathrm{O}}$) are not detected in RLAGNs. We intend to further investigate this issue in this work. A sample of 27 luminous sources (including 16 quasars and 11 high-excitation radio galaxies) was selected from the 3CRR catalog to reinvestigate the origin of X-ray emission in RLAGNs, where the X-ray and mid-infrared fluxes are observed by Chandra/XMM-Newton and Spitzer, respectively. It is found for the first time that there is a significant relationship between the mid-infrared to X-ray spectral index ${\alpha }_{\mathrm{IX}}$ and ${\lambda }_{\mathrm{IR}}$ for whole sample, while there is no relationship between ${\alpha }_{\mathrm{OX}}$ and ${\lambda }_{\mathrm{O}}$ in quasars. There are strong positive relationships between both $L_{\mathrm{R}}$-$L_{\mathrm{X}}$ and $L_{\mathrm{UV}}$-$L_{\mathrm{X}}$ panels, which can be well fitted by the disk-corona model. However, there is no significant relationship between $\Gamma$ and ${\lambda }_{\mathrm{IR}}$. The possible reason is related to the effects of the large-scale magnetic field in RLAGNs. We suggest that the X-ray emission in high-excitation RLAGNs originates from a disk-corona system.

7 pages, 7 figures, accepted for publication in A&A

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Cited by in corpus (1)

• Constraining X-ray emission of magnetically arrested disk (MAD) by radio-loud AGNs with extreme ultraviolet (EUV) deficit