Unifying static analysis of gravitational structures with a scale-dependent scalar field gravity as an alternative to dark matter

Abstract

Aims. We investigated the gravitational effects of a scalar field within scalar-tensor gravity as an alternative to dark matter. Motivated by chameleon, symmetron, and f (R)-gravity models, we studied a phenomenological scenario where the scalar field has both a mass (i.e. interaction length) and a coupling constant to the ordinary matter that scale with the local properties of the considered astrophysical system. Methods. We analysed the feasibility of this scenario using the modified gravitational potential obtained in its context and applied it to the galactic and hot gas/stellar dynamics in galaxy clusters and elliptical/spiral galaxies respectively. This is intended to be a first step in assessing the viability of this new approach in the context of "alternative gravity" models. Results. The main results are 1. the velocity dispersion of elliptical galaxies can be fitted remarkably well by the suggested scalar field, with model significance similar to a classical Navarro-Frenk-White dark halo profile; 2. the analysis of the stellar dynamics and the gas equilibrium in elliptical galaxies has shown that the scalar field can couple with ordinary matter with different strengths (different coupling constants), producing and/or depending on the different clustering state of matter components; 3. elliptical and spiral galaxies, combined with clusters of galaxies, show evident correlations among theory parameters, which suggest both the general validity of our results on all scales and a way toward a possible unification of the theory for all types of the gravitational systems we considered. All these results demonstrate that the proposed scalar field scenario can work fairly well as an alternative to dark matter.

The Dragonfly Nearby Galaxies Survey. III. The Luminosity Function of the M101 Group

“…The most popular interpretation nowadays to this lack of low mass galaxies is that the least massive sub-halos are likely to host extremely faint galaxies or even to be almost completely The dashed line is a fitted power law of the Milky Way and M31 dwarfs and the red stars are the inferred values for the M101 dwarfs, using the obtained relation. We also show measured values of the three out of the four brightest M101 already known satellites of M101 group as cyan circles (Ho et al 1997;Lelli et al 2013;Di Teodoro & Fraternali 2015;Salzano et al 2014;Leroy et al 2005). dark matter dominated.…”

“…The triangles are dSphs, blue from Milky Way (Boylan-Kolchin et al 2012), and purple from M31 (Tollerud et al 2014).The dashed line is a fitted power law of the Milky Way and M31 dwarfs and the red stars are the inferred values for the M101 dwarfs, using the obtained relation. We also show measured values of the three out of the four brightest M101 already known satellites of M101 group as cyan circles(Ho et al 1997;Lelli et al 2013;Di Teodoro & Fraternali 2015;Salzano et al 2014;Leroy et al 2005).…”

Einstein-Gauss-Bonnet dark matter halo: negative masses, rotation curves and the origin of dark matter effects

“…Combining equations (35) and (36), we find the expression of the coupling constant related to the Hubble parameter as follows:…”

“…[29,32] and also the hybrid description using the scalar field and density profiles [33,34]. Additionally, modifications involving scalartensor theories such as those in [35] present alternative gravitational frameworks where the gravitational constant becomes a function of the scalar field, leading to intriguing implications for cosmology and astrophysics. Moreover, we can refer to other successful modified theories in the context of galactic rotation curves, such as [36][37][38][39].…”