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arXiv 2309.04496astro-ph.EPastro-ph.SR
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原行星盘中 $M_{\mathrm{d}}/\dot M$ 的时间演化作为区分粘滞与 MHD 风的途径

The time evolution of $M_{\mathrm{d}}/\dot M$ in protoplanetary discs as a way to disentangle between viscosity and MHD winds

Alice Somigliana, Leonardo Testi, Giovanni Rosotti, Claudia Toci, Giuseppe Lodato, Benoît Tabone, Carlo Manara, Marco Tazzari

AI总结:

本研究提出通过盘群在盘质量-吸积率平面上分布范围随时间演化的差异来区分原行星盘的粘滞与 MHD 风模型,发现 MHD 主导下分布范围减小更慢,且该差异可被现有观测设施验证。

摘要:

由于低湍流的观测证据对原行星盘吸积的经典粘滞范式提出了挑战,MHD 盘风这一替代方案正被探索为有可能重现传统上用粘滞解释的相同观测特征。尽管这两种模型会导致不同的盘属性,但由于仪器限制,它们均未被观测排除。在本研究中,我们提出了一种可行的方法来区分粘滞和 MHD 框架,该方法基于盘群在盘质量($M_{\mathrm{d}}$)-吸积率($\dot M$)平面上分布的不同演化。通过解析计算与使用种群合成代码 \texttt{Diskpop} 进行的 1D 数值模拟的协同,我们发现这两种机制都预测盘群中观测到的 $M_{\mathrm{d}}/\dot M$ 比率的分布范围会随时间减小;然而,与纯粘滞主导的盘群相比,这种效应在 MHD 主导的盘群中要弱得多。此外,我们证明这种差异可以通过当前的观测设施检测到:我们展示了将内在分布范围与观测不确定性进行卷积并不会影响我们的结果,因为 MHD 情况下观测到的分布范围仍然显著大于粘滞情况。虽然目前可用的最新数据显示与风模型更为吻合,但使用 ALMA 和 ngVLA 获取直接气体质量测量的正在进行和未来的努力,将促使在不久的将来重新评估这一比较。

英文摘要:

As the classic viscous paradigm for protoplanetary disk accretion is challenged by the observational evidence of low turbulence, the alternative scenario of MHD disk winds is being explored as potentially able to reproduce the same observed features traditionally explained with viscosity. Although the two models lead to different disk properties, none of them has been ruled out by observations - mainly due to instrumental limitations. In this work, we present a viable method to distinguish between the viscous and MHD framework based on the different evolution of the distribution in the disk mass ($M_{\mathrm{d}}$) - accretion rate ($\dot M$) plane of a disk population. With a synergy of analytical calculations and 1D numerical simulations, performed with the population synthesis code \texttt{Diskpop}, we find that both mechanisms predict the spread of the observed ratio $M_{\mathrm{d}}/\dot M$ in a disk population to decrease over time; however, this effect is much less pronounced in MHD-dominated populations as compared to purely viscous populations. Furthermore, we demonstrate that this difference is detectable with the current observational facilities: we show that convolving the intrinsic spread with the observational uncertainties does not affect our result, as the observed spread in the MHD case remains significantly larger than in the viscous scenario. While the most recent data available show a better agreement with the wind model, ongoing and future efforts to obtain direct gas mass measurements with ALMA and ngVLA will cause a reassessment of this comparison in the near future.

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