Modelling clusters of galaxies byf(R) gravity

Abstract

We consider the possibility that masses and gravitational potentials of galaxy cluster, estimated at X‐ray wavelengths, could be explained without assuming huge amounts of dark matter, but in the context of f(R) gravity. Specifically, we take into account the weak field limit of such theories and show that the corrected gravitational potential allows to estimate the total mass of a sample of 12 clusters of galaxies. Results show that such a gravitational potential provides a fair fit to the mass of visible matter (i.e. gas + stars) estimated by X‐ray observations, without the need of additional dark matter while the size of the clusters, as already observed at different scale for galaxies, strictly depends on the interaction lengths of the corrections to the Newtonian potential.

Modeling halo mass functions in chameleonf(R)gravity

“…In §III B, we describe the spherical collapse model for f (R) gravity, discussing its application to excursion set theory in §III C. We examine the role of the environmental density in §III D and give details on the N -body simulations employed in our study in §III E. Note that we focus on cold dark matter halos formed in a f (R) model constructed as alternative to a cosmological constant. Galaxy clusters in the context of f (R) gravity in the absence of dark matter have been studied, e.g., in [33].…”

Testing an exactf(R)-gravity model at Galactic and local scales

“…It is also possible to show that f (R) theories can play a major role at astrophysical scales, due to the modifications of the gravitational potential in the low energy limit. Such a corrected potential reduces to the Newtonian one at the Solar System scale and could also offer the possibility of fitting galaxy rotation curves and galaxy cluster potentials without the need for large amounts of dark matter (Capozziello et al 2004(Capozziello et al , 2006(Capozziello et al , 2007a(Capozziello et al , 2009Milgrom 1983, Bekenstein 2004Sobouti 2007;Frigerio Martins & Salucci 2007;Mendoza & Rosas-Guevara 2007). However, extending the gravitational Lagrangian may give rise to many problems.…”

Relativistic Celestial Metrology: Dark Matter as an Inertial Gauge Effect

“…[59], there is a first attempt to fit some data of dark matter by using a Yukawa-like ansatz on the non-local York time of a galaxy. In each galaxy, the Yukawa-like potential of f ðRÞ theories [10][11][12] is put equal to a contribution to the extra potential depending on the non-local York time present in the lapse function appearing in Eq. (8); in this way, the good fits of the rotation curves of galaxies obtainable with f ðRÞ theories can be reproduced inside Einstein's GR as an inertial gauge effect.…”

“…There is the concrete possibility to explain the rotation curves of galaxies [14][15][16][17] as a relativistic inertial effect inside Einstein GR (choice of a non-local York time compatible with observations) without modifications: (a) of Newton gravity like in MOND [9]; (b) of GR like in f ðRÞ theories [10][11][12]; (c) of particle physics with the introduction of WIMPS [58].…”

“…However, to reconcile all the existing data with this 4-dimensional description, one must postulate the existence of dark matter and dark energy as the dominant components of the classical universe [6][7][8] after the recombination 3-surface (before it quantum mechanics is entering in the description and there is no acceptable description for the transition from quantum to classical astrophysics) already within galaxies before making the transition to cosmology and the replacement of ordinary space-time with the standard cosmological FLWR one, whose points describe a mean over a volume of 100 Mega-parsecs of the ordinary space-time. The attempts to avoid the appearance of "darkness" have led to many proposals of modifications of GR like MOND [9], f ðRÞ gravity [10][11][12] and the ones analyzed in Refs. [6][7][8].…”