猎户座四边形星团外围一颗年轻的、高度消光的褐矮星可能留下的尘埃尾迹
A possible trail of dust from a young, highly-extincted brown dwarf in the outskirts of the Trapezium Cluster
AI总结：
本文报道JWST在猎户座四边形星团外围发现一颗高度消光褐矮星及其约1700 au长的暗尘埃尾迹，提出尘埃颗粒尺寸增大可解释其观测特征，并探讨了辐射驱动盘风与邦迪-霍伊尔-利特尔顿吸积尾流两种可能的形成机制。
摘要：
我们报告了詹姆斯·韦布空间望远镜（JWST）在猎户座四边形星团外围发现的一颗高度消光（$A_V\sim52$）的候选褐矮星（$\sim0.018$M$_\odot$），它似乎与一条长约$\sim 1700\\,$au、宽度异常均匀的暗尾迹的末端重合，该尾迹在与点源相对的一端仅略微变宽。我们研究了与高度消光的褐矮星相关的尘埃尾迹是否有可能被JWST探测到，并探讨了其可能的起源。我们表明，如果尾迹中的尘埃颗粒比周围分子云中的尘埃更大，那么与褐矮星相关的尘埃尾迹是可以被观测到的。例如，如果周围分子云具有标准的$\sim0.25$$\mu$m最大颗粒尺寸，而尾迹中含有微米级颗粒，那么在NIRCam短波滤光片中，尾迹的散射不透明度将比周围环境高出一个数量级以上。我们使用一个简单模型表明，最大颗粒尺寸的变化可以再现观测到的高$A_V$以及尾迹与周围环境之间在多滤光片NIRCam观测中的对比度。我们提出并探讨了两种可能产生该尾迹的机制：i）由该区域O型星驱动的、来自褐矮星周盘的弱远紫外（FUV）辐射驱动风；ii）邦迪-霍伊尔-利特尔顿吸积尾流。前者将是四边形星团恒星辐射驱动盘风的最遥远已知案例，而后者将是高质量恒星形成区中星际介质向低质量天体发生“晚期”内落的第一个已知例子。
英文摘要：
We present the JWST discovery of a highly-extincted ($A_V\sim52$) candidate brown dwarf ($\sim0.018$M$_\odot$) in the outskirts of the Trapezium Cluster that appears to be coincident with the end of a $\sim 1700\,$au long, remarkably uniformly wide, dark trail that broadens only slightly at the end opposite the point source. We examine whether a dusty trail associated with a highly-extincted brown dwarf could plausibly be detected with JWST and explore possible origins. We show that a dusty trail associated with the brown dwarf could be observable if dust within it is larger than that in the ambient molecular cloud. For example, if the ambient cloud has a standard $\sim0.25$$μ$m maximum grain size and the trail contains micron-sized grains, then the trail will have a scattering opacity over an order of magnitude larger compared to the surroundings in NIRCam short-wavelength filters. We use a simple model to show that a change in maximum grain size can reproduce the high $A_V$ and the multi-filter NIRCam contrast seen between the trail and its surroundings. We propose and explore two possible mechanisms that could be responsible for the trail: i) a weak FUV radiation-driven wind from the circum-brown dwarf disc due to the O stars in the region and ii) a Bondi-Hoyle-Lyttleton accretion wake. The former would be the most distant known case of the Trapezium stars' radiation driving winds from a disc, and the latter would be the first known example of ``late'' infall from the interstellar medium onto a low mass object in a high-mass star-forming region.
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