Extended Data Fig. 7: Effective length of the Perseus cluster.

(a) A sketch of the effective length concept in a stratified cluster atmosphere. The length along the LOS, which corresponds to the region size that contributes most to the measured flux/spectra, increases with the projected distance from the cluster center. (b) A radial profile of the normalized X-ray surface brightness in Perseus, adapted from¹¹, is shown in black. The effective length, defined as the region size where 50% of the flux is collected, is shown with the red curve. The shaded red region indicates the scales associated with 40–60% of the flux contribution. The blue dashed curve represents the X-ray-weighted LOS length scale.