AI 中文总结
本研究利用SMA对金牛座10个暗弱II类原行星盘进行200-400 GHz巡天，发现其谱指数与更亮盘无系统性差异，暗盘高频光学深度不低，谱指数低值或源于尘埃自散射或自由-自由发射污染。
AI 中文摘要
我们利用亚毫米波阵列（Submillimeter Array, SMA）对金牛座-御夫座区域的10个II类原行星盘进行了198.0-407.5 GHz宽波段光谱观测。这些天体的337 GHz流量密度（$F_{\rm 337 GHz}$）范围为8.2-34 mJy。这10个II类盘的198-358 GHz谱指数（$α_{198-358}$）的中位数和标准差分别为1.9和0.3。与近期另一项针对47个在（亚）毫米波段更亮的II类盘（$F_{\rm 337 GHz}\rm\thicksim$20-730 mJy）的同类SMA巡天相比，没有证据表明这10个新观测的更暗弱II类盘的$α_{198-358}$值存在系统性差异。在>230 GHz的频率下，这10个更暗弱II类盘的光学深度可能与更亮源的光学深度相当，可达$\rm\thicksim$5以上。此外，部分暗弱天体中低于2.0的$α_{198-358}$低值，可通过最大尘埃颗粒尺寸（$a_{\rm max}$）约100 $μ$m的尘埃自散射效应，或自由-自由发射的污染来解释。
英文摘要
We have performed Submillimeter Array (SMA) observations of 198.0-407.5 GHz broadband spectra of 10 Class II protoplanetary disks in the Taurus-Auriga region. The 337 GHz flux densities ($F_{\rm 337 GHz}$) of these objects are in the range of 8.2-34 mJy. The median and standard deviation of the 198-358 GHz spectral indices ($α_{198-358}$) of these 10 Class II disks are 1.9 and 0.3, respectively. Compared to the recent, similar SMA survey on another 47 Class II disks that are brighter at (sub)millimeter bands ($F_{\rm 337 GHz}\sim$20-730 mJy), there is no evidence that these newly observed 10 fainter Class II disks have systematically different $α_{198-358}$ values. At $>$230 GHz frequencies, the optical depths of these 10 fainter Class II disks may be as high as those of the brighter sources, which may be $\gtrsim$5. In addition, the low ($<$2.0) values of $α_{198-358}$ in some faint objects may be explained by the effect of dust self-scattering, with maximum dust grain size ($a_{\rm max}$) $\sim$ 100 $μ$m, or by contamination by free-free emission.
Commentsaccepted by The Astronomical Journal
