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arXiv 2007.02583astro-ph.GA
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低表面亮度星系中暗物质的可能物态方程

The Possible Equation Of State Of Dark Matter in Low Surface Brightness Galaxies

Xiaobo Gong, Meirong Tang, Zhaoyi Xu

摘要:

观测到的低表面亮度(LSB)星系的自转曲线在研究暗物质中起着重要作用,它表明存在一个中心等密度暗物质核。然而,冷暗物质的宇宙学N体模拟预测了一个具有幂律质量密度分布的内部尖状晕,并且不能再现中央恒定密度的核心。这种现象被称为尖点核问题。当暗物质处于静止状态并满足流体静力平衡条件时,利用状态方程可以得到静止球对称时空中的密度分布。为了解决尖点核问题,我们假设状态方程与标度变换无关。它对这类物态方程的低阶近似自然会导致一种特殊情况,即$p=ζρ+2εV_{rot}^{2}ρ$,其中$p$和$ρ$是压力和密度,$V_{rot}$是星系的自转速度,$ζ$和$ ε$是正常数。当$ε$在$0.15$附近时,可以得到类似于伪等温晕模型的密度分布。为了得到一个应用更广泛的模型,在状态方程中加入多方模型,即$p= \fracζ{ρ_{0}^{s}}ρ^{1+s}+ 2εV_{rot}^{2}ρ$,可以得到其它类型的密度分布,如与Burkert分布相近的密度分布,其中$s$和$ρ_{0}$为正常数。

英文摘要:

The observed rotation curves of low surface brightness (LSB) galaxies play an essential role in studying dark matter, and indicate that there exists a central constant density dark matter core. However, the cosmological N-body simulations of cold dark matter predict an inner cusped halo with a power-law mass density distribution, and can't reproduce a central constant-density core. This phenomenon is called cusp-core problem. When dark matter is quiescent and satisfies the condition for hydrostatic equilibrium, using the equation of state can get the density profile in the static and spherically symmetric space-time. To solve the cusp-core problem, we assume that the equation of state is independent of the scaling transformation. Its lower order approximation for this type of equation of state can naturally lead to a special case, i.e. $p=ζρ+2εV_{rot}^{2}ρ$, where $p$ and $ρ$ are the pressure and density, $V_{rot}$ is the rotation velocity of galaxy, $ζ$ and $ ε$ are positive constants. It can obtain a density profile that is similar to the pseudo-isothermal halo model when $ε$ is around $0.15$. To get a more widely used model, let the equation of state include the polytropic model, i.e. $p= \fracζ{ρ_{0}^{s}}ρ^{1+s}+ 2εV_{rot}^{2}ρ$, we can get other kinds of density profiles, such as the profile that is nearly same with the Burkert profile, where $s$ and $ρ_{0}$ are positive constants.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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