We use a subsample of co-detections of the ACT and MaDCoWS cluster catalogs to verify the predicted relation between the observed X-ray flux FX in the 0. 5−2 keV band and the cluster mass M500c for halos at z > 0. 6 − 0. 7. We modified this relation by introducing a correction coefficient, η, which is supposed to encapsulate factors associated with a particular method of flux estimation, the sample selection function, the definition of the cluster mass. We show that the X-ray flux, being the most basic X-ray observable, serves as a convenient and low-cost mass indicator for distant galaxy clusters with photometric or even missing redshifts (by setting z = 1) as long as it is known that z ≳ 0. 6 − 0. 7. The correction coefficient η is ≈0. 8 if M^UPP₅₀₀₂ from the ACT-DR5 catalog are used as cluster masses, whereas η ≈ 1. 1 if weak-lensing-calibrated masses M^Cal₅₀₀₂ are used instead.
Lyskova et al. (Fri,) studied this question.