Schwarzschild-like Black Hole in Dark Matter Halo: Analysis of Perturbations and Radiation Properties

The interplay between black holes and dark matter represents a crucial frontier in astrophysics, and recent research explores how dark matter environments alter fundamental black hole properties. Akshat Pathrikar from Ahmedabad University leads a study investigating a black hole resembling the Schwarzschild solution, but immersed within a specific type of dark matter halo. The team analyses how this dark matter halo influences various aspects of the black hole, including its natural oscillations, the way it emits Hawking radiation, and even its apparent shadow as observed from Earth. This combined approach allows scientists to place constraints on the properties of dark matter itself, offering a novel pathway to understanding this elusive substance and its impact on the most extreme objects in the universe.

Black Hole Ringdown and Quasi-Normal Modes

This collection of research papers and preprints details extensive investigation into black hole physics and gravitational waves. The dominant theme centres on calculating and analysing quasinormal modes (QNMs) of black holes, both within the framework of general relativity and in modified gravity theories. QNMs are essential for understanding how black holes settle down after a disturbance, such as a merger, and reveal information about their properties like mass and spin. Studies explore QNMs in various scenarios, including standard Schwarzschild and Kerr black holes, charged and rotating Reissner-Nordström and Kerr-Newman black holes, and in the context of modified gravity theories, such as Einstein-Gauss-Bonnet gravity and non-commutative spacetimes.

A strong connection exists with gravitational wave astronomy, aiming to model gravitational wave signals accurately, test general relativity, and investigate black hole shadows. Scientists also explore the quantum properties of black holes, including Hawking radiation and black hole thermodynamics, and some studies consider the impact of dark matter and dark energy on black hole characteristics. This represents a comprehensive overview of current research in black hole physics, focused on testing general relativity, exploring modified gravity, and understanding gravitational wave observations.

Dark Matter Haloes and Black Hole Perturbations

Scientists investigated how dark matter influences astrophysical black holes by modelling a black hole within a Dehnen-type dark matter halo. This study pioneers a combined analysis of scalar, electromagnetic, and gravitational perturbations to understand how dark matter affects black hole behaviour. Researchers computed quasinormal modes (QNMs) using the Wentzel-Kramers-Brillouin (WKB) approximation, enhanced with Padé approximants to improve accuracy and convergence. This technique allows precise determination of the frequencies at which a black hole oscillates after being disturbed. The research team further investigated particle and photon trajectories around the black hole, revealing how the dark matter halo alters their paths and influences observational signatures.

Crucially, scientists employed black hole shadow observations as a means to constrain the parameters defining the dark matter halo, effectively linking theoretical models to potential observational data. This involved meticulous calculations of the black hole’s apparent size and shape as seen from a distant observer. To complete the analysis, the study examined greybody factors associated with Hawking radiation for various perturbation spins, providing insights into the rate at which black holes emit radiation and lose mass. This combined approach delivers a comprehensive understanding of how dark matter environments modify black hole oscillations, radiation properties, and corresponding observational signatures.

Dark Matter Shifts Black Hole Spacetime Geometry

Scientists have meticulously mapped the spacetime around a black hole immersed in a dark matter halo, revealing how the distribution of dark matter alters the gravitational landscape. The research team solved Einstein’s field equations to derive a metric describing this combined black hole-dark matter system, utilizing a Dehnen-type density profile to characterize the halo’s mass distribution. This yielded a spacetime geometry where the metric function asymptotically approaches unity at large distances, consistent with flat spacetime, but is demonstrably shifted by the presence of the dark matter halo. The team determined the enclosed mass profile of the dark matter halo and incorporated this into the spacetime metric.

Analysis shows that increasing the halo’s density or scale radius subtly shifts the metric function towards larger radial distances, indicating an enhancement of the overall gravitational potential due to the dark matter. Further investigation involved analysing the behaviour of scalar and electromagnetic perturbations within this spacetime. Scientists derived a wave equation governing these perturbations, revealing an effective potential that dictates their propagation. This potential is influenced by the black hole’s mass, the perturbation’s spin, and the parameters defining the dark matter halo. The team’s calculations demonstrate how the dark matter halo modifies the effective potential, altering the frequencies at which these perturbations can exist and propagate around the black hole. This detailed mapping of spacetime and perturbation behaviour provides a crucial framework for interpreting observational signatures of black holes residing within dark matter environments.

Dark Matter Shapes Black Hole Dynamics

This research presents a comprehensive analysis of how dark matter environments influence the behaviour of astrophysical black holes. By modelling a black hole within a Dehnen-type dark matter halo, scientists investigated perturbations in scalar, electromagnetic, and gravitational fields, alongside particle motion and black hole shadow characteristics. The team employed the Wentzel-Kramers-Brillouin approximation to calculate quasinormal modes and greybody factors, revealing how the presence of dark matter alters these fundamental properties and potentially affects observable signals. The findings demonstrate that dark matter significantly impacts black hole dynamics and radiation, offering a means to probe both black hole physics and the nature of dark matter itself. Specifically, the study establishes a connection between the parameters of the dark matter halo and the observable characteristics of the black hole, such as its shadow and emitted radiation. Future work could focus on refining these models and comparing the results with observational data from gravitational wave detectors or black hole imaging projects, potentially providing crucial insights into the elusive nature of dark matter and testing the limits of general relativity in strong gravitational fields.