Shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant

We study the dynamics of (i) neutral test particles, (ii) magnetically charged test particles, and (iii) test magnetic dipole around a regular Bardeen black hole surrounded by perfect fluid dark matter (PFDM). It has been shown how the magnetic charge of the black hole and the parameter of the surrounding PFDM can influence the innermost stable circular orbit (ISCO) radius of a test particle. We have found that the ISCO radius is strongly affected as a consequence of the combined effect of the magnetic charge parameter and the perfect fluid dark matter. The black hole magnetic charge parameter g and the combined effect of perfect fluid dark matter can mimic the black hole rotation parameter up to a/M ≈ 0.9. It has been observed that the ISCO for magnetic dipole disappears at the values exceeding the calculated upper value for the magnetic interaction parameter β. The upper limit decreases with the increase of both the dark matter and magnetic charge parameters. Finally, as an astrophysical application, we have analyzed degeneracy effects of spin of Kerr black holes and magnetic charge of regular Bardeen black holes for the different values of the dark matter parameter providing exactly the same value for ISCO radius of a magnetic dipole with the same value of the parameter β = 10.2 of the magnetar called PSR J1745-2900 orbiting around supermassive black hole Sagittarius A*. It has been observed that the magnetic charge of the pure regular Bardeen black hole can mimic the spin of a Kerr black hole up to a/M 0.8085, while upper limit for the magnetic charge which may provide ISCO for the magnetic dipole is gupper 0.65M . In the presence of PFDM with the parameter α = 0.01(0.05), the upper limit for the magnetic charge decreases and equals to gupper 0.62M (0.548M ) and consequently mimicker value for the spin parameter of black hole lies in the range of a/M ∈ (0.0106 ÷ 0.8231) ( a/M ∈ (0.0816 ÷ 0.8595)). We also show that the same values of the spin of Kerr black hole and the magnetic charge of regular Bardeen black hole surrounded by PFDM provide the same values for the ISCO radius of the chosen magnetar.

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“…Consequently, taking into account Eqs. (28) and (24) one may rewrite the interaction term in the following form…”

Section: Magnetic Dipole Motionmentioning

confidence: 99%

Dynamics of test particles around a Bardeen black hole surrounded by perfect fluid dark matter

et al. 2020

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“…Dark matter has not been so far detected directly, yet astrophysical observations indicate that many giant elliptical and spiral galaxies contain a (sometimes a binary) supermassive black hole in the galactic center embedded in a giant dark matter halo [3,4,[65][66][67][68]. In the literature, several black hole solutions with a dark matter background have been proposed (see for example [69][70][71][72][73][74][75][76][77][78]). The analysis of the accretion process for different spherically symmetric spacetime geometries for a static fluid and the accretion of phantom energy onto a stationary charged black hole has been investigated testing under various conditions (see for example [79,80]).…”

Section: Introductionmentioning

confidence: 99%

Testing the weak cosmic censorship conjecture for a Reissner–Nordström–de Sitter black hole surrounded by perfect fluid dark matter

2021

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In this paper, we test the weak cosmic censorship conjecture (WCCC) for the Reissner–Nordström–de Sitter (RN-dS) black hole surrounded by perfect fluid dark matter. We consider a spherically symmetric perturbation on deriving linear and non-linear order perturbation inequalities by applying a new version of gedanken experiments well accepted from the work of Sorce and Wald. Contrary to the well-known result that the Reissner–Nordström (RN) black hole could be overcharged under linear order particle accretion it is hereby shown that the same black hole in perfect fluid dark matter with cosmological parameter cannot be overcharged. Considering a realistic scenario in which black holes cannot be considered to be in vacuum we investigate the contribution of dark matter and cosmological constant in the overcharging process of an electrically charged black hole. We demonstrate that the black hole can be overcharged only when two fields induced by dark matter and cosmological parameter are completely balanced. Further we present a remarkable result that a black hole cannot be overcharged beyond a certain threshold limit for which the effect arising from the cosmological constant dominates over the effect by the perfect fluid dark matter. Thus even for a linear accretion process, the black hole cannot always be overcharged and hence obeys the WCCC in general. This result would continue to be fulfilled for non-linear order accretion.

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“…This is because the spacetime is not asymptotically flat and hence it does not allow the limit of bu R → 0 and bu S → 0. However, from a physical point of view, we know that an observed star or galaxy is located at a finite distance from us [70,72]. In other words, we can consider only finitedistance corrections in this case, one can include only a certain finite distance which leads to the further simplified relationŝ…”

Section: Angular Radius Of the Shadowmentioning

confidence: 99%

Optical properties of a Brane-World black hole as photons couple to the Weyl tensor

Zhang

Liu

et al. 2020

Eur. Phys. J. C

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In this article, we have investigated the equations of motion of the photons coupled to Weyl tensor by the geometric optics approximation and the corresponding shadow in a Brane-World black hole spacetime. It is shown that there exists a double shadow for a black hole since the coupling photons with different polarization directions propagate along different paths in the spacetime. Furthermore, we discuss the effects of the metric parameter α related to the cosmological constant, X-cold dark matter parameter β and the coupling parameter λ on the umbra (the overlap region of the double shadow) and the penumbra. We also obtain the finite-distance corrections to the deflection angle of light in the Brane-World black hole spacetime as the photons coupled to Weyl tensor by using a recent geometric method.

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Shadow and deflection angle of rotating black holes in perfect fluid dark matter with a cosmological constant

Cited by 179 publications

References 51 publications

Dynamics of test particles around a Bardeen black hole surrounded by perfect fluid dark matter

Dynamics of test particles around a Bardeen black hole surrounded by perfect fluid dark matter

Testing the weak cosmic censorship conjecture for a Reissner–Nordström–de Sitter black hole surrounded by perfect fluid dark matter

Optical properties of a Brane-World black hole as photons couple to the Weyl tensor

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