Accretion Disk Luminosity for Black Holes Surrounded by Dark Matter with Anisotropic Pressure

We investigate the luminosity of the accretion disk of a static black hole surrounded by dark matter with anisotropic pressure. We calculate all basic orbital parameters of test particles in the accretion disk, such as angular velocity, angular momentum, energy, and radius of the innermost circular stable orbit as functions of the dark matter density, radial pressure, and anisotropic parameter, which establishes the relationship between the radial and tangential pressures. We show that the presence of dark matter with anisotropic pressure makes a noticeable difference in the geometry around a Schwarzschild black hole, affecting the radiative flux, differential luminosity, and spectral luminosity of the accretion disk

Motion of stars near the galactic center

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Analysis of dark matter profiles in the halos of spiral galaxies

The distribution of dark matter in the low surface brightness spiral galaxies U5750, U11454, U11819, and U11648 is analyzed by utilizing well-established density profiles from existing literature. These profiles include the Beta, Brownstein, Burkert, exponential sphere, pseudo-isothermal, and Persic profiles. For simplicity, we assume spherically symmetric distribution of dark matter in the considered galaxies, without accounting for their intricate structural complexities. For each density profile, we fit the rotation curve data to the aforementioned galaxies. Employing Markov Chain Monte Carlo statistical analyses, we infer model-free parameters from the rotation curves, namely the characteristic (central) density and scale radius. This enables us to estimate the total dark matter mass within the galactic halos. To identify the best-fit profile, we employ the Bayesian Information Criterion. Additionally, we adopt the Levenberg-Marquardt nonlinear least squares approach for the purpose of comparison and completeness. Through our statistical analysis, we offer a physical interpretation behind the selection of specific profiles. This interpretation is based on the insights obtained from the analyses

Physical properties of dark matter in galaxy U11454

In this paper physical characteristics of dark matter distribution in the spiral galaxy U11454 is explored using only well-known cored density profiles in the literature such as the pseudo-isothermal, Burkert, Einasto, exponential sphere, Beta and Brownstein profiles. It is presumed that the distribution of dark matter in the considered galaxy is spherically symmetric without taking into account its complex structural components. It is assumed that dark matter possesses non-vanishing pressure which allows theoretically analyzing the state parameter. The model free parameters of each profile are inferred from the rotation curve data of the galaxy by means of non-linear model fit procedure. Using the Bayesian Information Criterion the best fit profile among the considered ones is selected. Furthermore, the hydrostatic equilibrium equation is solved and the pressure profiles for each above mentioned density profile are constructed in the weak gravitational field regime. Combining the pressure and corresponding density profiles one gains equations of state for the dark matter in the galaxy U11454. The mass and gravitational potential are evaluated and constructed as a function of the radial distance for each profile. The total dark matter mass is assessed and our results are confronted and contrasted with the previous outcomes. In addition, the speed of sound is estimated in the dark matter distribution and it is shown that its behavior is quite unusual especially for the Brownstein profile. Finally, the refracting index is calculated in order to assess gravitational lensing effects produce

ACCRETION DISK LUMINOSITY FOR BLACK HOLES SURROUNDED BY DARK MATTER WITH ANISOTROPIC PRESSURE

We investigate the luminosity of the accretion disk of a static black hole surrounded by dark matter with anisotropic pressure. We calculate all basic orbital parameters of test particles in the accretion disk, such as angular velocity, angular momentum, energy, and radius of the innermost circular stable orbit as functions of the dark matter density, radial pressure, and anisotropic parameter, which establishes the relationship between the radial and tangential pressures. We show that the presence of dark matter with anisotropic pressure makes a noticeable difference in the geometry around a Schwarzschild black hole, affecting the radiative flux, differential luminosity, and spectral luminosity of the accretion disk

ACCRETION DISK LUMINOSITY FOR BLACK HOLES SURROUNDED BY DARK MATTER WITH ANISOTROPIC PRESSURE

We investigate the luminosity of the accretion disk of a static black hole surrounded by dark matter with anisotropic pressure. We calculate all basic orbital parameters of test particles in the accretion disk, such as angular velocity, angular momentum, energy, and radius of the innermost circular stable orbit as functions of the dark matter density, radial pressure, and anisotropic parameter, which establishes the relationship between the radial and tangential pressures. We show that the presence of dark matter with anisotropic pressure makes a noticeable difference in the geometry around a Schwarzschild black hole, affecting the radiative flux, differential luminosity, and spectral luminosity of the accretion disk

Re-Establishing Naturally Reproducing Sturgeon Populations in the Caspian Basin: A Wicked Problem in the Ural River

Although Eurasia’s Caspian basin once supported the world’s richest and most diverse complex of sturgeon species, recent human activities have decimated populations of these ecologically and economically important fish. All five anadromous Caspian sturgeon species are critically endangered, and the potamodromous sterlet is also threatened. The precipitous decline of these species is due to a combination of factors that includes illegal, unreported, and unregulated (IUU) fishing; destruction of feeding and spawning habitat; water pollution; and the environmental consequences of climate change. International efforts are currently underway to re-establish sustained naturally reproducing sturgeon populations in the basin. Here, we update and review the status of sturgeon in the Caspian Sea with emphasis on the northern basin and the inflowing Volga and Ural rivers. We then focus on efforts to restore sturgeon in the Ural, which originates in Russia and flows through Kazakhstan before entering the Caspian Sea. With nearly ideal hydrological conditions for sturgeon, the Ural is the basin’s sole remaining river that allows migrating sturgeon unimpeded access to potentially productive spawning grounds. The challenge of re-establishing sturgeon in the Ural River exhibits the classical characteristics of wicked problems: ambiguous definitions, changing assumptions and unanticipated consequences, tradeoffs and economic dependencies, an incomplete and contradictory knowledge base, and no straightforward pathway toward a final solution. This challenge is examined here for the first time from the perspective of its wicked dynamics, with consideration given to approaches that have proven effective elsewhere in resolving wicked environmental problems