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tokens: values of FWHM, namely ∣〈FWHM〉 N − 〈FWHM〉 N−1 ∣. The results of this analysis, for N up to 100, are presented in the left panel of Figure 7 . As shown in the figure, the mean FWHM converges to ≃2.85 px after only about 20 iterations, N, at which point the standard error of the mean, which decreases as (as in fact expected for a normal distribution of FWHM values with a standard deviation of the population Σ) exceeds the differential error ∣〈FWHM〉 N − 〈FWHM〉 N−1 ∣. Figure 7. Left: the estimated mean FWHM of the PSF modeled with 2D Gaussian, 〈FWHM〉 N ± Σ N , as a function of the number N of PSF simulations performed (upper panel); the successive difference in the mean values ∣〈FWHM〉 N − 〈FWHM〉 N−1 ∣, along with the standard error of the mean Σ N (dashed curve), are shown on the lower panel. Right: histogram of the emerging FWHM values after 100 PSF simulations, along with the best-fit normal distribution returning 〈FWHM〉 100 ≃ 2.84 px and Σ ≃ 0.21 px. Right panel of Figure 7 presents the histogram of the emerging FWHM values after 100 PSF simulations along with the best-fit normal distribution returning, 〈FWHM〉 100 ≃ 2.84 px and Σ ≃ 0.21 px. Given this, the radius for the extraction region encompassing 3 σ of the photons from a point source formally reads as, px. However, the source PSF is not well represented by a 2D Gaussian and particularly with limited photon statistics, broad wings of the PSF do matter. To illustrate this, in Figure 8 we plot the enclosed photon count fraction for each simulated PSF. As shown, the real 2 σ radius ranges between 2.5 px and 5 px, depending on a particular PSF realization, and the 3 σ radius is, in all cases, at ∼10 px. Hence, in the analysis of the surface brightness presented in this paper, instead of a 2D Gaussian approximation, we build a table model for the core PSF as a result from the averaging of over 100 PSF simulations. Figure 8. Enclosed count fraction for 100 simulated PSF images; horizontal dotted lines from bottom to top correspond to 1 σ , 2 σ , and 3 σ count fractions, respectively. Appendix B Surface Brightness Profiles Along and Across the Jet Axis We have also extracted the radial profiles of the net counts separately for the four quadrants of the concentric annular regions centered on the CGCG 292−057 nucleus, oriented to the east, to the west, to the north, and to the south from the center. The east and west quadrants correspond therefore to the surface brightness profiles along the axis of the inner jets in the system, while the north and south quadrants to the surface brightness profiles across the jet axis. Due to the limited photon statistics in separate quadrants, we had to increase the size of the annuli from 2 px (as adopted in Figure 3 ) up to 7 px. The resulting profiles are presented in Figure 9 . Figure 9. X-ray surface brightness profiles resulting from extracting the net counts from four quadrants of a concentric stack of annular regions (each with the bin size of 7 px)