标题： FAUST 第26卷。 原恒星包层的尘埃 opacity 光谱指数弥合了星际介质和盘之间的差距。 显示英文标题

标题： FAUST XXVI. The dust opacity spectral indices of protostellar envelopes bridge the gap between interstellar medium and disks

摘要： 亚毫米波尘埃吸收谱指数是一项关键的可观测量，用于限制尘埃性质，例如观测到的尘埃群体的最大颗粒尺寸。 它已经在星系尺度上以及原行星盘中被广泛测量。 然而，由于观测和分析上的挑战，在滋养新生原恒星及其盘的包层中测量尘埃性质存在相当大的差距。 为了填补这一空白，我们利用了来自 ALMA FAUST 大型项目的 1.2 毫米和 3.1 毫米的灵敏尘埃连续辐射数据，并约束了一组原恒星周围的尘埃吸收毫米波谱指数。 我们的高分辨率数据，连同相对于以往工作的更精细方法论，使我们在 uv 平面上能够区分盘和包层的贡献，从而测量未受内部区域厚发射污染的包层的谱指数。 首先，我们发现年轻的盘较小且光学厚度较大。 其次，我们测量了 11 个源的包层尺度上的尘埃吸收谱指数：其中 9 个源的 β 值在文献中从未被限制过。 我们有效地将这些尺度上已测量尘埃吸收谱指数 β 的源数量增加了一倍。 第三，结合现有的文献测量与我们自己的测量（总计 n=18），我们展示了包层的谱指数如何分布在类似星际介质 (ISM) 和类似盘的值之间，弥合了推断尘埃演化中的差距。 最后，我们统计上证实了 β 与原恒星包层质量之间显著的相关性，这在文献中之前已被暗示。 我们的研究结果表明，从星际介质 (ISM) 到包层再到盘，尘埃光学性质平滑变化。 需要多波长巡天来进一步这项研究，并对从云到盘路径上的尘埃演化做出更普遍的结论。 显示英文摘要

摘要： The sub-millimetre dust opacity spectral index is a critical observable to constrain dust properties, such as the maximum grain size of an observed dust population. It has been widely measured at galactic scales and down to protoplanetary disks. However, because of observational and analytical challenges, quite a gap exists in measuring dust properties in the envelopes that feed newborn protostars and their disks. To fill this gap, we use sensitive dust continuum emission data at 1.2 and 3.1 mm from the ALMA FAUST Large Program and constrain the dust opacity millimetre spectral index around a sample of protostars. Our high-resolution data, along with a more refined methodology with respect to past efforts, allow us to disentangle disk and envelope contributions in the uv-plane, and thus measure spectral indices for the envelopes uncontaminated by the optically thick emission of the inner regions. First, we find that the young disks are small and optically thick. Secondly, we measure the dust opacity spectral index at envelope scales for n=11 sources: the beta of n=9 sources had never been constrained in the literature. We effectively double the number of sources for which the dust opacity spectral index beta has been measured at these scales. Third, combining the available literature measurements with our own (total n=18), we show how envelope spectral indices distribute between ISM-like and disk-like values, bridging the gap in the inferred dust evolution. Finally, we statistically confirm a significant correlation between beta and the mass of protostellar envelopes, previously suggested in the literature. Our findings indicate that the dust optical properties smoothly vary from the ISM, through envelopes and all the way down to disks. Multi-wavelength surveys are needed to further this study and make more general claims on dust evolution in its pathway from cloud to disks.