Observed L_X − T relation based on TR18 CSF simulation. The TR18 NR, CSF, and AGN models are shown in red (dash-dotted), purple (dotted), and blue (dashed) lines. The gray, black, and blue data points represent the simulations with masses of M₅₀₀ = 10¹³ M_⊙, 5 × 10¹³ M_⊙, and 10¹⁴ M_⊙ respectively. The number of data points are the expected number of groups to be detected by ATHENA for the TR18 CSF model (which is given in the middle values in Table 2). No data points are shown for the mass of M₅₀₀ = 10¹³ M_⊙ beyond z ≥ 1.0 due to the zero detection probability predicted in panel 5 of Fig. 9. The solid green line is the linear fit result with a fixed slope from the TR18 CSF model.