1. Introduction  
2. Methods  
2.1. X-ray luminosity  
2.2. Galaxy samples  
2.3. Simulation datasets and computation of the intrinsic X-ray emission  
3. Results  
4. Discussion  
4.1. Comparing $L_{\mathrm{X,CGM}}-M_{500c}$ to self-similar model  
4.2. Comparison to cosmological galaxy simulations  
5. Summary and conclusions