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Research in the radio/X-ray correlation of hard X-ray selected Seyfert galaxies sample
2021-05-26| 【A A A【Print】【Close】

Almost every galaxy contains a supermassive black hole (SMBH) at its centre. The SMBH will become active when surrounding material is captured by the black hole (BH) gravitational potential well, forming an accretion disc and emitting multi-wavelength emissions. The whole system is named Active Galactic Nuclei (AGN). The structure of an AGN is quite complex. Emission at different wavebands may originate from different physical components and different emission mechanisms. The radio-loud AGNs usually show a jetted morphology in radio images, and the hard X-rays likely originate from the accretion disk-corona. These physical components may also be correlated with the accretion rate and the mass of the BH directly or indirectly.

Galaxies and Cosmology Research Group of Xinjiang Astronomical Observatory has conducted an investigation of the Fundamental Plane (FP) of BH activity based on INTEGRAL hard X-ray-selected sample of Seyfert galaxies. The analysis of FP would reveal the correlation of the accretion and jet of AGNs, also the origin of X-ray emission. This paper is published in the Monthly Notice of Royal Astronomical Society (MNRAS, 2021, 503, 1987).

The sample includes 64 sources, among which 35 are Seyfert 1s (Seyfert 1-1,5) and 29 are Seyfert 2s (Seyfert 1.9-2.0). The researchers classify the sources according to various properties, i.e., Seyfert classification, radio loudness and radio morphology. They first investigate the distribution of X-ray flux ratio (i.e., hard X-ray flux to X-ray flux, LHX/LX) and the X-ray flux in Eddington units (i.e.,LX/LEdd), find that there is no evident dependence of the  LHX/LX on LX/LEdd as shown in Figure 1. This result implies that, the X-ray emission of this sample may originate from the same radiation mechanism which could be from hot accretion flow (or corona in case of cold accretion-disk).  Due to the large scatter of the distribution of BH mass, this work explored only the correlation of radio luminosity and X-ray luminosity in Eddington units. Despite the different classification of the sources, the whole sample follows the similar correlation with the slope of 0.77+0.10 (the black solid line in Figure 2), which agrees with the standard FP at level. Under the interpretation of radio emission from the jet, this result implies that the jet of Seyfert galaxies may be formed from similar mechanism. Furthermore, the researchers find out that the jet production efficiency is decreasing with the X-ray luminosity as shown in Figure 3. 


Figure 1. Distribution of the 20–100 to 2–10 keV X-ray flux ratio  versus 2–10 keV X-ray Eddington ratio .


Figure 2. Radio/X-ray correlation (in Eddington units) for Seyfert galaxies, the black solid curve represents the fitting to the whole sample.


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Contact: CHANG Ning

Xinjiang Astronomical Observatory, Chinese Academy of Sciences


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