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arXiv 2405.04749astro-ph.HE
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贝叶斯黑洞摄影测量

Bayesian Black Hole Photogrammetry

Harvard University(哈佛大学);Black Hole Initiative at Harvard University(哈佛黑洞倡议);Center for Astrophysics | Harvard & Smithsonian(天体物理中心 | 哈佛与史密森尼)

Dominic O. Chang, Michael D. Johnson, Paul Tiede, Daniel C. M. Palumbo

AI总结:

该研究提出了一种双锥吸积模型,用于分析EHT观测的黑洞图像,并通过贝叶斯推断确定质量-距离比和倾角的范围。

摘要:

我们提出了一种简单的、解析的双锥吸积模型,用于低亮度活动星系核(LLAGN)核心的视界尺度图像,包括事件视界望远镜(EHT)观测到的图像。我们的基础模型是来自轴对称、磁化的等离子体的同步辐射,该模型被限制在两个方向相反且与黑洞自转轴对齐的锥体中。我们证明该模型能够准确重现各种时间平均广义相对论磁流体动力学(GRMHD)模拟的图像,能够准确恢复这些模拟中的黑洞和发射参数,并且足够高效,可用于在射电干涉数据中通过贝叶斯推断框架测量这些参数。我们还表明,源图像中的非平凡拓扑结构在应用于稀疏阵列(如2017年EHT M87*观测)的观测时,可能导致非平凡的多模态解。这些退化性凸显了在解释EHT测量时采用能够充分采样后验空间的贝叶斯技术的重要性。我们拟合了该模型到EHT对M87*的观测,并发现质量-距离比θ_g的95%最高后验密度区间(HPDI)为(2.84,3.75)μas,以及倾角θ_o的范围为(11°,24°)。这些新测量与EHT和恒星动力学估计的质量测量(例如Gebhardt等,2011;EHTC等,2019a,b;Liepold等,2023)以及M87*喷流属性推断出的自转轴倾角(例如Walker等,2018)一致。

英文摘要:

We propose a simple, analytic dual-cone accretion model for horizon scale images of the cores of Low-Luminosity Active Galactic Nuclei (LLAGN), including those observed by the Event Horizon Telescope (EHT). Our underlying model is of synchrotron emission from an axisymmetric, magnetized plasma, which is constrained to flow within two oppositely oriented cones that are aligned with the black hole's spin axis. We show that this model can accurately reproduce images for a variety of time-averaged general relativistic magnetohydrodynamic (GRMHD) simulations, that it accurately recovers both the black hole and emission parameters from these simulations, and that it is sufficiently efficient to be used to measure these parameters in a Bayesian inference framework with radio interferometric data. We show that non-trivial topologies in the source image can result in non-trivial multi-modal solutions when applied to observations from a sparse array, such as the EHT 2017 observations of M87${}^*$. The presence of these degeneracies underscores the importance of employing Bayesian techniques that adequately sample the posterior space for the interpretation of EHT measurements. We fit our model to the EHT observations of M87${}^*$ and find a 95% Highest Posterior Density Interval (HPDI) for the mass-to-distance ratio of $θ_g\in(2.84,3.75)\,μ{\rm as}$, and give an inclination of $θ_{\rm o}\in(11^\circ,24^\circ)$. These new measurements are consistent with mass measurements from the EHT and stellar dynamical estimates (e.g., Gebhardt et al. 2011; EHTC et al. 2019a,b; Liepold et al. 2023), and with the spin axis inclination inferred from properties of the M87${}^*$ jet (e.g., Walker et al. 2018).

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