The radial acceleration relation in galaxy clusters

Abstract

Recently, the discovery of the radial acceleration relation (RAR) in galaxies has been regarded as an indirect support of alternative theories of gravity such as Modified Newtonian Dynamics (MOND) and modified gravity. This relation indicates a tight correlation between dynamical mass and baryonic mass in galaxies with different sizes and morphology. However, if the RAR relation is scale-independent and could be explained by alternative theories of gravity, this relation should be universal and true for galaxy clusters as well. In this article, by using the x-ray data of a sample of galaxy clusters, we investigate if there exists any tight correlation between dynamical mass and baryonic mass in galaxy clusters, assuming hot gas mass distribution almost representing baryonic distribution and that the galaxy clusters are virialized. We show that the resulting RAR of 52 non-cool-core galaxy clusters scatters in a large parameter space, possibly due to our simplifying assumptions and unclear matter content in galaxy clusters. This might indicate that the RAR is unlikely to be universal and scale-independent.

Observational constraints on the slope of the radial acceleration relation at low accelerations

“…Though the measurements are more difficult than for late types, early type galaxies seem to lie on the relation (Lelli et al 2017), while galaxy clusters seem to lie well above the relation (Chan & Del Popolo 2020). Interestingly, g † may vary from galaxy-to-galaxy (Rodrigues et al 2018;Chan & Del Popolo 2020;Zobnina & Zasov 2020). The significance of the small scatter of the relation has been debated (e.g.…”

“…1 is universal has been called into question (e.g. Rodrigues et al 2018;Stone & Courteau 2019;Chan & Del Popolo 2020;Zobnina & Zasov 2020). Stone & Courteau (2019) further suggest that the scatter may be much larger than claimed by McGaugh et al (2016).…”

Heat capacity of Holographic screen inspires MOND theory

“…On the other, it is also seen that the MOND acceleration is a function of Planck acceleration, and additionally, Planck mass may be accepted as a candidate for the mass content of each degree of freedom of holographic screen. Therefore, in general, our approach has two (three) free parameters in ultra-relativistic (non-relativistic) case including q and g (q, g, and m), if we do not limit ourselves to a special MOND acceleration [7][8][9][10][11] and m (in nonrelativistic case). In both cases, any restrictions on the value of MOND acceleration (such as accepting a value for it [6]) leads to eliminate one of the parameters q and g with the help of Eqs.…”

“…[12] that estimates μ ≃ C 2NP azy . As we mentioned in the introduction, while Milgrom found a 0 is of order of 10 −8 cm s −2 [2], the case of a 0 = 1.2 × 10 −8 cm s −2 is the most probable [5,6], and indeed, the constancy (uniqueness) of the value of MOND acceleration is still controversial [7][8][9][10]. On the other, gravity is the result of the existence of mass (energy), and thus, the amount of mass is reflected in the power of gravity.…”

“…( 1) and compatibility with observations. On the other, debates on the possible values of MOND acceleration is still ongoing [7][8][9][10][11]. Indeed, while Medium-richness galaxy groups can help us in testing MOND at very low accelerations, it seems that this theory can not solve the problem of mass in galaxy clusters and also rich galaxy groups [6].…”