A SPITZER SURVEY OF MID-INFRARED MOLECULAR EMISSION FROM PROTOPLANETARY DISKS. I. DETECTION RATES
A SPITZER SURVEY OF MID-INFRARED MOLECULAR EMISSION FROM PROTOPLANETARY DISKS. I. DETECTION RATES
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DOI：
10.1088/0004-637x/720/1/887
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发表时间：
2010-06
期刊：
影响因子：
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通讯作者：
K. Pontoppidan;C. Salyk;G. Blake;R. Meijerink;J. Carr;J. Najita
中科院分区：
文献类型：
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作者：
K. Pontoppidan;C. Salyk;G. Blake;R. Meijerink;J. Carr;J. Najita
我们提出了一个斯皮策光谱仪搜索10-36 μm的分子发射的原行星盘的大样本，包括线从H2O，OH，C2 H2，HCN，和CO2。本文介绍了样品和数据处理，并推导出中红外分子发射检测率与恒星质量的函数关系。样本涵盖了从早期M到A的光谱类型范围，并补充了A和B星周围圆盘的档案光谱。它来自附近的各种恒星形成区域，包括蛇夫座、狼座和变色龙。显示强发射线的光谱用于识别哪些线是盘内各种物理和化学条件的最佳示踪剂。总之，我们确定了22 T金牛星具有较强的中红外H2O发射。综合水线光度（也就是检测到水蒸气的位置）介于5 × 10−4至9 × 10−3 L之间，这可能使水成为经典金牛座T型恒星内部盘面的主要冷却剂。在样品中的五个过渡盘中没有一个显示出可检测的气体分子发射，斯皮策上限在1%的水平上的线与连续比（除了H2），但样品太小，无法得出结论，这是否是过渡盘的一般性质。我们发现一个很强的依赖检测率与光谱类型;在我们的25颗A型和B型恒星的样本周围，没有发现在中红外波段表现出水辐射，低至1%-2%的线-连续谱比，而晚型恒星（M-G）周围一半以上的盘显示出足够强的水辐射，可以被斯皮策探测到，对于K星周围的盘，探测率接近2/3。一些Herbig Ae/Be星在20 μm以上显示出1%-2%水平的H2O/OH发射特征，其中一颗星还显示出CO2的发射。我们认为，所观察到的金牛座T磁盘和赫比格Ae/Be磁盘之间的差异是由于不同的激发和/或化学光谱类型的依赖，并建议光化学可能发挥重要的作用，在可观察到的中红外分子线发射的特性，从原行星盘。
We present a Spitzer InfraRed Spectrometer search for 10–36 μm molecular emission from a large sample of protoplanetary disks, including lines from H2O, OH, C2H2, HCN, and CO2. This paper describes the sample and data processing and derives the detection rate of mid-infrared molecular emission as a function of stellar mass. The sample covers a range of spectral type from early M to A, and is supplemented by archival spectra of disks around A and B stars. It is drawn from a variety of nearby star-forming regions, including Ophiuchus, Lupus, and Chamaeleon. Spectra showing strong emission lines are used to identify which lines are the best tracers of various physical and chemical conditions within the disks. In total, we identify 22 T Tauri stars with strong mid-infrared H2O emission. Integrated water line luminosities, where water vapor is detected, range from 5 × 10−4 to 9 × 10−3 L☉, likely making water the dominant line coolant of inner disk surfaces in classical T Tauri stars. None of the five transitional disks in the sample show detectable gaseous molecular emission with Spitzer upper limits at the 1% level in terms of line-to-continuum ratios (apart from H2), but the sample is too small to conclude whether this is a general property of transitional disks. We find a strong dependence on detection rate with spectral type; no disks around our sample of 25 A and B stars were found to exhibit water emission, down to 1%–2% line-to-continuum ratios, in the mid-infrared, while more than half of disks around late-type stars (M-G) show sufficiently intense water emission to be detected by Spitzer, with a detection rate approaching 2/3 for disks around K stars. Some Herbig Ae/Be stars show tentative H2O/OH emission features beyond 20 μm at the 1%–2% level, however, and one of them shows CO2 in emission. We argue that the observed differences between T Tauri disks and Herbig Ae/Be disks are due to a difference in excitation and/or chemistry depending on spectral type and suggest that photochemistry may be playing an important role in the observable characteristics of mid-infrared molecular line emission from protoplanetary disks.