http://arxiv.org/abs/2202.07404
There had been recent advancement toward the detection of ultra-faint dwarf galaxies, which may serve as a useful laboratory for dark matter exploration since some of them contains almost 99$\%$ of pure dark matter. The majority of these galaxies contain no black hole that inhabits them. Recently, there had been reports that some dwarf galaxies may have a black hole within. In this study, we construct a black hole solution combined with the Dehnen dark matter halo profile, which is commonly used for dwarf galaxies. We aim to find out whether there would be deviations relative to the standard black hole properties which might allow determining whether the dark matter profile in ultra-faint dwarf galaxies is cored or cuspy. To make the model more realistic, we applied the modified Newman-Janis prescription to obtain the rotating metric. We analyzed the black hole properties such as the event horizon, ergoregion, geodesics of time-like and null particle, and the black hole shadow. To broaden the scope of this study, we also calculated the weak deflection angle to examine the effect of the Dehnen profile. Results revealed that the Dehnen profile causes some tiny but interesting deviations to the known black hole properties. It is shown that the radius of the innermost stable circular orbit decreases, while the photonsphere radius increases. We also found out that the size of the shadow decreases due to the Dehnen profile and the extent depends on whether the profile is cored or cuspy. Overall, the deviation caused by the Dehnen profile relative to the known black hole properties are so tiny, that one needs a very sophisticated and ultra-sensitive space detectors to help distinguish whether this profile for ultra-faint dwarf galaxy is cored or cuspy.
R. Pantig and A. Övgün
Wed, 16 Feb 22
28/69
Comments: 18 pages, 10 figures. Comments are welcome
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