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Table 2.

Priors and posteriors for the HOD and the derived parameters on the five volume-limited eRASS1 samples (see Table 1 and Fig. 1).

Parameter Prior Posterior
S0 S1 S2 S3 S4
Mmin 𝒰(13.0, 16.0) 14.73 0.35 + 0.93 $ ^{+0.93}_{-0.35} $ 14.90 0.24 + 0.87 $ ^{+0.87}_{-0.24} $ 14.94 0.26 + 0.84 $ ^{+0.84}_{-0.26} $ 15.02 0.63 + 0.63 $ ^{+0.63}_{-0.63} $ 15.04 0.72 + 0.61 $ ^{+0.61}_{-0.72} $
σlogM 𝒰(0.01, 2.0) 0.82 0.46 + 0.49 $ ^{+0.49}_{-0.46} $ 0.66 0.34 + 0.50 $ ^{+0.50}_{-0.34} $ 0.62 0.32 + 0.46 $ ^{+0.46}_{-0.32} $ 0.58 0.40 + 0.23 $ ^{+0.23}_{-0.40} $ 0.57 0.37 + 0.20 $ ^{+0.20}_{-0.37} $
αsat 𝒰(0.1, 3) 1.25 0.54 + 0.89 $ ^{+0.89}_{-0.54} $ 1.48 0.60 + 0.85 $ ^{+0.85}_{-0.60} $ 1.41 0.58 + 0.82 $ ^{+0.82}_{-0.58} $ 1.65 0.93 + 1.04 $ ^{+1.04}_{-0.93} $ 1.67 1.08 + 1.05 $ ^{+1.05}_{-1.08} $
Msat 𝒰(13.0, 16.5) 15.32 0.33 + 0.34 $ ^{+0.34}_{-0.33} $ 15.70 0.27 + 0.30 $ ^{+0.30}_{-0.27} $ 15.63 0.28 + 0.29 $ ^{+0.29}_{-0.28} $ 15.79 0.30 + 0.36 $ ^{+0.36}_{-0.30} $ 15.76 0.35 + 0.42 $ ^{+0.42}_{-0.35} $
αinc Fixed 0.55 0.55 0.55 0.55 0.55
Minc Fixed 14.87 14.95 15.06 15.16 15.25

fsat < 14.9% < 9.3% < 9.9% < 6.8% < 8.1%
b 2.95 ± 0.21 3.35 ± 0.23 3.69 ± 0.27 4.15 ± 0.42 4.34 ± 0.62
M halo ¯ $ \overline{M_{\mathrm{halo}}} $ [1014M] 3.09 ± 0.48 3.54 ± 0.51 3.83 ± 0.55 4.44 ± 0.89 4.38 ± 1.11
L X ¯ $ \overline{L_{\mathrm{X}}} $ [1043 erg s−1] 4.63 ± 0.97 7.38 ± 0.98 10.21 ± 0.98 13.68 ± 0.99 17.76 ± 0.99

Notes. 𝒰(min, max) indicates a uniform prior between minimum and maximum values. The parameters with fixed prior were estimated using the eRASS1 digital twin (Seppi et al. 2022). The bottom part of the table shows derived parameters: the fraction of satellites fsat (see Eq. (9)), the large-scale halo bias, and the average halo mass. The average X-ray luminosity for each sample is reported in the last row. The upper limits extend to the 84th percentile.

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