Galactic rotation dynamics in Gogoi-Goswami $f(\mathcal{R})$ gravity model

Abstract

We propose to test the viability of the recently introduced Gogoi-Goswami model in the galactic scales. For this purpose we consider test particles moving in stable circular orbits around the galactic center. We study the Palatini approach of f (R) gravity via Weyl transformation, which is the frame transformation from the Jordan frame to the Einstein frame. We derive the expression of rotational velocities of test particles in the Gogoi-Goswami model. For the observational data of samples of high surface brightness and low surface brightness galaxies, we show that the predicted rotation curves are well fitted with observations, thus implying that this model can explain flat rotation curves of galaxies. We also study an ultra diffuse galaxy, AGC 242019 which has been claimed in literature to be a dark matter dominated galaxy similar to low surface brightness galaxies with a slowly rising rotation curve. The rotation curve of this galaxy also fits well with the model prediction in our study. Furthermore, we studied the Tully-Fisher relation for the entire sample of galaxies and found that the model prediction shows the consistency with the data.

Weak gravitational lensing and shadow cast by rotating black holes in axionic Chern–Simons theory

“…Black holes and gravitational waves (GWs) are two most significant successful predictions of GR. However, despite its successes, GR fails to explain two most prominent observational phenomena: the accelerated expansion of the Universe [2,3] and the need for exotic matter to describe the galactic dynamics [4][5][6][7][8], among others [9,10]. These failures of GR specified two roads for reckoning the observed facts: either the Universe is filled with mysterious dark energy and dark matter [11][12][13][14][15][16], or some sort of modifications are needed for GR in such a way that the correct outcomes of such modifications can explain the corresponding observational data.…”