Detection level (in σ units) of the X-ray simulated substructures (50 ks exposures) versus redshift. Lower panel: 2.0 × 10⁴⁴ erg/s cluster + 0.4 × 10⁴⁴ erg/s subcluster (close 2.0_0.4) and 2.0 × 10⁴⁴ erg/s cluster + 1.0 × 10⁴⁴ erg/s subcluster (close 2.0_1.0). Separated by 6 px in both cases. Middle panel: 5.0 × 10⁴⁴ erg/s cluster + 1.0 × 10⁴⁴ erg/s subcluster (close 5.0_1.0) and 5.0 × 10⁴⁴ erg/s cluster + 2.5 × 10⁴⁴ erg/s subcluster (close 5.0_2.5). Separated by 6 px in both cases. Upper panel: 5.0 × 10⁴⁴ erg/s cluster + 1.0 × 10⁴⁴ erg/s subcluster (distant 5.0_1.0) and 5.0 × 10⁴⁴ erg/s cluster + 2.5 × 10⁴⁴ erg/s subcluster (distant 5.0_2.5). Separated by 12 px in both cases. When the line stops, it means that the subcluster is no longer detected. The close 2.0_0.4 configuration, for example, provides detections of the subcluster only up to z = 0.5 at the 2.5σ level.