The generalized scaling relations for X-ray galaxy clusters: the most powerful mass proxy

TL;DR

This paper extends generalized scaling relations for X-ray galaxy clusters, demonstrating their effectiveness as precise mass proxies with minimal scatter, and provides mass estimates for numerous clusters based on these relations.

Contribution

It introduces an extended formalism of gSR in the self-similar model and identifies the most efficient observed relations for mass estimation.

Findings

gSR projections are the most efficient relations for mass recovery

Intrinsic scatter reduced to below 16% in mass estimates

Mass estimates have a typical error of 3-5% for clusters

Abstract

The application to observational data of the generalized scaling relations (gSR) presented in Ettori et al. (2012) is here discussed. We extend further the formalism of the gSR in the self-similar model for X-ray galaxy clusters, showing that for a generic relation M_tot ~ L^a M_g^b T^c, where L, M_g and T are the gas luminosity, mass and temperature, respectively, the values of the slopes lay in the plane 4*a+3*b+2*c=3. Using published dataset, we show that some projections of the gSR are the most efficient relations, holding among observed physical X-ray quantities, to recover the cluster mass. This conclusion is based on the evidence that they provide the lowest chi^2, the lowest total scatter and the lowest intrinsic scatter among the studied scaling laws on both galaxy group and cluster mass scales. By the application of the gSR, the intrinsic scatter is reduced in all the cases down to a relative error on M_tot below 16 per cent. The best-fit relations are: M_tot ~ M_g^a T^{1.5-1.5a}, with a~0.4, and M_tot ~ L^a T^{1.5-2a}, with a~0.15. As a by product of this study, we provide the estimates of the gravitating mass at Delta=500 for 120 objects (50 from the Mahdavi et al. 2013 sample, 16 from Maughan 2012; 31 from Pratt et al. 2009; 23 from Sun et al. 2009), 114 of which are unique entries. The typical relative error in the mass provided from the gSR only (i.e. not propagating any uncertainty associated with the observed quantities) ranges between 3-5 per cent on cluster scale and is about 10 per cent for galaxy groups. With respect to the hydrostatic values used to calibrate the gSR, the masses are recovered with deviations in the order of 10 per cent due to the different mix of relaxed/disturbed objects present in the considered samples. In the extreme case of a gSR calibrated with relaxed systems, the hydrostatic mass in disturbed objects is over-estimated by about 20 per cent.