The envelopes and disks that surround protostars reflect the initial conditions of star and planet formation and govern the assembly of stellar masses. Characterizing these structures requires observations that span the near-IR to centimeter wavelengths. Consequently, the past two decades have seen progress driven by numerous advances in observational facilities across this spectrum, including the Spitzer Space Telescope, Herschel Space Observatory, the Atacama Large Millimeter/submillimeter Array, and a host of other ground-based interferometers and single-dish radio telescopes. ▪Nearly all protostars have well-formed circumstellar disks that are likely to be rotationally supported; the ability to detect a disk around a protostar is more a question of spatial resolution rather than whether or not a disk is present.▪The disks around protostars have inherently higher millimeter/submillimeter luminosities as compared to disks around more-evolved pre-main-sequence stars, though there may be systematic variations between star-forming regions.▪The envelopes around protostars are inherently asymmetric, and streamers emphasize that mass flow through the envelopes to the disks may not be homogeneous.▪The current mass distribution of protostars may be impacted by selection bias given that it is skewed toward solar-mass protostars, which is inconsistent with the stellar initial mass function.

中文翻译：

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原恒星系统结构的观测视图


围绕原恒星的包络和盘反映了恒星和行星形成的初始条件，并控制着恒星质量的组装。表征这些结构需要从近红外到厘米波长的观测。因此，在过去的二十年里，这一光谱的观测设施取得了许多进步，包括斯皮策太空望远镜、赫歇尔太空天文台、阿塔卡马大型毫米/亚毫米阵列以及许多其他地面干涉仪和单碟射电望远镜。▪几乎所有的原恒星都有形状良好的星际盘，这些盘很可能是旋转支撑的;探测到原恒星周围盘的能力更多的是空间分辨率的问题，而不是盘是否存在的问题。▪与更进化的前主序星周围的盘相比，原恒星周围的盘本身具有更高的毫米/亚毫米光度，尽管恒星形成区域之间可能存在系统性的变化。▪原恒星周围的包络线本质上是不对称的。 并且 streamers 强调通过包络流向盘的质量流可能不是均匀的。▪当前原恒星的质量分布可能会受到选择偏差的影响，因为它偏向于太阳质量的原恒星，这与恒星初始质量函数不一致。