Brown dwarf disks are excellent laboratories to test our understanding of disk physics in an extreme parameter regime. In this paper we investigate a sample of 29 well-characterized brown dwarfs and very low mass stars, for which Herschel far-infrared fluxes as well as (sub)-mm fluxes are available. We have measured new Herschel PACS fluxes for 11 objects and complement these with (sub)-mm data and Herschel fluxes from the literature. We analyze their spectral energy distributions in comparison with results from radiative transfer modeling. Fluxes in the far-infrared are strongly affected by the shape and temperature of the disk (and hence stellar luminosity), whereas the (sub)-mm fluxes mostly depend on disk mass. Nevertheless, there is a clear correlation between far-infrared and (sub)-mm fluxes. We argue that the link results from the combination of the stellar mass-luminosity relation and a scaling between disk mass and stellar mass. We find strong evidence of dust settling to the disk midplane. The spectral slopes between near- and far-infrared are mostly between $-0.5$ and $-1.2$ in our sample, comparable to more massive T Tauri stars, which may imply that the disk shapes are similar as well, though highly-flared disks are rare among brown dwarfs. We find that dust temperatures in the range of 7-15 K, calculated with $T\approx25\,(L/L_\odot)^{0.25}$ K, are appropriate for deriving disk masses from (sub)-mm fluxes for these low luminosity objects. About half of our sample hosts disks with at least one Jupiter mass, confirming that many brown dwarfs harbour sufficient material for the formation of Earth-mass planets in their midst.
Linking low- to high-mass YSOs with Herschel-HIFI observations of water
水能有效地探测年轻恒星（YSO）的动力学，特别是分子外流中的冲击。它是探索低质量原恒星的物理特性是否可以外推到大质量YSO的关键分子。作为WISH关键计划的一部分，我们研究了沿流出腔壁的冲击动力学和激发条件与源亮度的函数关系。分析了52个YSO的H2O 988、752、1097 GHz和12 CO J=10-9、16-15谱线的速度分辨赫歇尔-HIFI光谱，这些YSO的辐射热光度（L_bol）范围为<1 to >10^5 L_sun。H2O线的轮廓是相似的，表明它们探测的是相同的气体。我们看到两个主要的高斯发射组件在所有YSO：一个广泛的组件与非解离的冲击在流出腔壁（腔冲击）和一个狭窄的组件与静态信封材料。H_2O谱线（L_H_2O）总积分强度的60%以上来自空腔激波分量。所有YSO的H2O线宽相似，而12 CO 10-9的线宽随L_bol略有增加。用非LTE辐射转移代码RADEX进行的腔激波分量的激发分析显示，高质量YSO的752 GHz发射更强，这可能是由于红外辐射场的泵浦。正如以前发现的CO，一个很强的相关性与斜率单位测得的日志（L_H2O）和日志（L_bol），这可以外推到河外的来源。我们的结论是，广泛的组成部分的H2O和高J CO线起源于所有YSO的流出腔壁的冲击，而低J CO过渡主要跟踪夹带流出气体。与低质量天体相比，高质量天体的紫外线场和湍流运动更高，这可能解释了12…
Benchmark Brown Dwarfs as Chemical Laboratories: Linking System Bulk Properties to Atmospheric Retrievals
University of Hertfordshire（赫特福德大学）；American Museum of Natural History（美国自然历史博物馆）；The Graduate Center City University of New York（纽约市立大学研究生中心）；Hunter College, City University of New York（纽约市立大学亨特学院）
