多方暗物质流体的晕结构和引力透镜特征
Halo structure and lensing signatures of a polytropic dark matter fluid
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中文总结 AI 辅助
研究暗物质最小有效压力能否修改晕结构并保留ΛCDM模型优点，考虑特定正压关系，计算相关剖面，发现其能在一定程度上改变透镜特征，引入新参数且在特定极限下可简化为无碰撞冷暗物质。
中文摘要 AI 辅助
我们研究暗物质领域中的最小有效压力是否能在保留成功的Λ冷暗物质（ΛCDM）模型大规模预测的同时修改非线性晕结构。我们考虑正压关系\(P = K\rho^{\gamma}\)，其中\(\gamma = 3/2\)，这被解释为在晕化区域对Jeans层级的有效粗粒化闭合。在此框架下，暗物质在宇宙学密度下仍有效无压力，但在坍缩晕内部发展出有限的有效声速。对于\(\gamma = 3/2\)，平衡晕构型对应\(n = 2\)的Lane-Emden解，产生具有二次中心扁平化的有限半径密度分布。嵌入ΛCDM晕的经验浓度-质量关系时，所得核心尺度在矮星系到星系质量范围内仅表现出微弱的质量依赖性。对于产生千秒差距尺度核心的参数值，背景膨胀历史和密度扰动的线性增长在观测上与ΛCDM难以区分，而当今的Jeans尺度仍局限于亚百万秒差距长度。我们计算了该模型的投影表面密度和弱引力透镜收敛剖面。相对于质量匹配的Navarro-Frenk-White晕，该模型预测中心透镜振幅有适度抑制，而收敛功率谱仅在足够高的多极处被修改。该模型引入一个控制非线性压力支持的额外参数，并在\(K\rightarrow0\)的极限下连续简化为无碰撞冷暗物质。
英文摘要
We investigate whether a minimal effective pressure in the dark matter sector can modify nonlinear halo structure while preserving the successful large-scale predictions of the $Λ$ cold dark matter ($Λ$CDM) model. We consider a barotropic relation $P=Kρ^γ$ with $γ=3/2$, interpreted as an effective coarse-grained closure of the Jeans hierarchy in virialized regions. In this framework, dark matter remains effectively pressureless at cosmological densities while developing a finite effective sound speed inside collapsed halos. For $γ=3/2$, equilibrium halo configurations correspond to the $n=2$ Lane--Emden solution, producing finite-radius density profiles with quadratic central flattening. When embedded within the empirical concentration--mass relation of $Λ$CDM halos, the resulting core scale exhibits only weak mass dependence across dwarf-to-galaxy mass ranges. For parameter values yielding kiloparsec-scale cores, the background expansion history and linear growth of density perturbations remain observationally indistinguishable from $Λ$CDM, while the present-day Jeans scale remains confined to sub-megaparsec lengths. We compute projected surface-density and weak-lensing convergence profiles for the model. Relative to mass-matched Navarro--Frenk--White halos, the model predicts a moderate suppression of the central lensing amplitude, while the convergence power spectrum is modified only at sufficiently high multipoles. The model introduces a single additional parameter controlling nonlinear pressure support and continuously reduces to collision-free cold dark matter in the limit $K\rightarrow0$.
