Light deflection angle through velocity profile of galaxies in f(R) model
Vipin Kumar Sharma, Bal Krishna Yadav, Murli Manohar Verma
Abstract
Abstract We explore a new realisation of the galactic scale dynamics via gravitational lensing phenomenon in power-law f ( R ) gravity theory of the type $$f(R)\propto R^{1+\delta }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>f</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>R</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>∝</mml:mo> <mml:msup> <mml:mi>R</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mi>δ</mml:mi> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> with $$\delta<<1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>δ</mml:mi> <mml:mo><</mml:mo> <mml:mo><</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> for interpreting the clustered dark matter effects. We utilize the single effective point like potential (Newtonian potential + f ( R ) background potential) obtained under the weak field limit to study the combined observations of galaxy rotation curve beyond the optical disk size and their lensing profile in f ( R ) frame work. We calculate the magnitude of light deflection angle with the characteristic length scale (because of Noether symmetry in f ( R ) theories) appearing in the effective f ( R ) rotational velocity profile of a typical galaxy with the model parameter $$\delta \approx O(10^{-6})$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>δ</mml:mi> <mml:mo>≈</mml:mo> <mml:mi>O</mml:mi> <mml:mo>(</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> constrained in previous work. For instance, we work with the two nearby controversial galaxies NGC 5533 and NGC 4138 and explore their galactic features by analysing the lensing angle profiles in f ( R ) background. We also contrast the magnitudes of f ( R ) lensing angle profiles and the relevant parameters of such galaxies with the generalised pseudo-isothermal galaxy halo model and find consistency.