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arXiv 2407.07770astro-ph.GA
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NGC 1052-DF2暗物质晕建模的挑战:核型晕模型与尖型晕模型的对比

Challenges in modeling the dark matter halo of NGC 1052-DF2: Cored versus cuspy halo models

K. Aditya

AI总结:

本研究针对NGC 1052-DF2暗物质质量估算的模型简并问题,通过各向异性分布函数和MCMC方法对比核型与尖型暗物质晕模型,排除了尖型晕模型,发现核型晕模型拟合更优但受数据约束有限,该星系可能存在符合标准恒星-晕质量关系的超弥散暗物质分布。

摘要:

NGC 1052-DF2的发现及后续建模研究表明,该星系暗物质含量匮乏,且与标准的恒星-晕质量比存在冲突。本研究旨在破解NGC 1052-DF2质量估算中动力学模型之间的简并问题。我们采用各向异性分布函数构建了NGC 1052-DF2的质量模型,该函数包含随径向变化的各向异性参数,并探究了各类模型参数对暗物质估算结果的影响。我们将观测到的恒星光度测量数据作为输入参数构建分布函数,并运用马尔可夫链蒙特卡洛(Markov Chain Monte Carlo, MCMC)方法估算暗物质模型参数。研究发现,带有尖型暗物质晕的质量模型的χ²值与零暗物质模型的χ²值相当。此外,尖型暗物质晕无法一致地解释该星系内部和外部区域观测到的速度弥散。据此,我们排除了用尖型暗物质晕描述NGC 1052-DF2质量模型的可能性。我们的研究显示,总质量为log(M_DM/M_⊙)=10.5的核型暗物质晕模型能够解释观测到的运动学特征,但需要极大的标长(20千秒差距)和外截断半径(26千秒差距)。尽管核型质量模型的拟合效果相对更好,但我们的研究结果强调,现有运动学数据对质量模型的约束非常有限。我们的结果表明,NGC 1052-DF2可能不仅具有超弥散的恒星分布,而且在现有运动学数据的不确定性范围内,它可能还拥有超弥散的暗物质分布,这与星系形成和演化模型预测的标准恒星-晕质量关系(stellar-to-halo mass relation, SHMR)是相容的。

英文摘要:

The discovery of NGC 1052-DF2 and subsequent modeling have shown that NGC 1052-DF2 is deficient in dark matter and is in conflict with the standard stellar-to-halo mass ratio. In this work, we aim to resolve the degeneracy between the dynamical models on the mass estimate of the NGC 1052-DF2.We constructed mass models of NGC 1052-DF2 using an anisotropic distribution function with a radially varying anisotropy parameter and studied the effect of the various model parameters on the dark matter estimates. We used the observed stellar photometry as an input parameter to construct the distribution function and employed a Markov Chain Monte Carlo (MCMC) method to estimate the dark matter model parameters.We find that mass models with a cuspy dark matter halo have comparable $χ^{2}$ to models with zero dark matter. Moreover, the cuspy dark matter halo fails to consistently account for the observed velocity dispersion in the inner and outer regions of the galaxy. Consequently, we rule out the possibility of a cuspy dark matter halo for describing the mass models of NGC 1052 - DF2. Our study shows that the cored dark matter halo model with a total mass of $\log(M_{DM}/M_{\odot})=10.5$ explains the observed kinematics but requires an extraordinarily large scale length (20kpc) and an outer cutoff radius (26kpc). While the cored mass model provides a comparatively better fit, our findings emphasize that the mass models are largely unconstrained by the available kinematic data. Our results suggest that NGC 1052 - DF2 may not only have an ultra-diffuse stellar distribution but that it can, within uncertainties in the available kinematic data, potentially host an ultra-diffuse dark matter distribution compatible with the standard stellar-to-halo mass relation (SHMR) predicted by galaxy formation and evolution models

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