CO emission from discs around isolated HAeBe and Vega-excess stars
CO emission from discs around isolated HAeBe and Vega-excess stars
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孤立的 HAeBe 和 Vega 过剩恒星周围圆盘的 CO 排放
DOI：
10.1111/j.1365-2966.2005.08938.x
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发表时间：
2005
影响因子：
4.8
通讯作者：
I. Coulson
中科院分区：
文献类型：
--
作者：
W. Dent;J. Greaves;I. Coulson
我们描述的结果从J = 3 - 2 12 CO排放的可见星分类为具有红外过剩的调查。在21个天体中清晰地检测到了这条线，并且在红外线超过0.01的目标中（56%的天体）发现了大量的分子气体（10 −3木星质量），但在红外线超过0.01的目标中（10%的天体）却很少见。一个简单的几何参数的基础上的红外过量意味着光盘的张开角通常是12毫米的对象与检测到的CO;在这个角度内，光盘是光学厚恒星辐射和屏蔽的CO从光解。两个或三个CO盘具有异常低的红外过量（0.01），这意味着屏蔽盘在物理上非常薄（1 μ m）。大约50%的检测到的线轮廓是双峰，而其余的许多显着扩大线，归因于光盘开普勒旋转。简单的模型拟合线轮廓表明外半径在30 - 300 Au范围内，比通过拟合连续体SED发现的要大，但与主序星周围碎片盘的大小相似。多达五个的外半径小于太阳系（50 Au），另外四个在半径小于20 Au的圆盘中显示出气体的证据。外盘半径与恒星光谱类型（从K到B 9）无关，但有证据表明半径与总尘埃质量之间存在相关性。此外，平均盘的大小似乎随着时间的推移而减少：年龄在3-7百万年的恒星周围的盘的平均半径为210 Au，而年龄在7-20百万年的盘则小了三倍。这表明，在行星形成区域之外存在着大量的气体（至少2百万年），最多可达1.77亿年，并可能在这一区域内再存在1.11亿年。唯一真正的碎片盘与检测到的CO是HD 9672，这表明了一个双峰CO的配置文件，是最紧凑的气体盘观察到的，与模拟的外半径为17 Au。在HD 141569的情况下，详细的线轮廓模型表明气体可能位于两个环中，半径为90和250 Au，类似于散射光和中红外线中看到的尘埃结构。在AB Aur和HD 163296中，我们还发现分子盘和尘埃散射盘的尺寸相似;这表明分子气体和小尘埃颗粒紧密共存。行星系统：原行星盘-亚毫米。
We describe results from a survey for J = 3‐2 12 CO emission from visible stars classified as having an infrared excess. The line is clearly detected in 21 objects, and significant molecular gas (10 −3 Jupiter masses) is found to be common in targets with infrared excesses 0.01 (56 per cent of objects), but rare for those with smaller excesses (∼10 per cent of objects). A simple geometrical argument based on the infrared excess implies that disc opening angles are typically 12 ◦ for objects with detected CO; within this angle, the disc is optically thick to stellar radiation and shields the CO from photodissociation. Two or three CO discs have an unusually low infrared excess (0.01), implying the shielding disc is physically very thin (1 ◦ ). Around 50 per cent of the detected line profiles are double-peaked, while many of the rest have significantly broadened lines, attributed to discs in Keplerian rotation. Simple model fits to the line profiles indicate outer radii in the range 30‐300 au, larger than found through fitting continuum SEDs, but similar to the sizes of debris discs around main-sequence stars. As many as five have outer radii smaller than the Solar System (50 au), with a further four showing evidence of gas in the disc at radii smaller than 20 au. The outer disc radius is independent of the stellar spectral type (from K through to B9), but there is evidence of a correlation between radius and total dust mass. Also the mean disc size appears to decrease with time: discs around stars of age 3-7 Myr have a mean radius ∼210 au, whereas discs of age 7-20 Myr are a factor of three smaller. This shows that a significant mass of gas (at least 2 M⊕ )e xists beyond the region of planet formation for up to ∼7 Myr, and may remain for a further ∼10 Myr within this region. The only bona fide debris disc with detected CO is HD9672; this shows a double-peaked CO profile and is the most compact gas disc observed, with a modelled outer radius of 17 au. In the case of HD141569, detailed modelling of the line profile indicates gas may lie in two rings, with radii of 90 and 250 au, similar to the dust structure seen in scattered light and the mid-infrared. In both AB Aur and HD163296 we also find that the sizes of the molecular disc and the dust scattering disc are similar; this suggests that the molecular gas and small dust grains are closely co-located. Ke yw ords: planetary systems: proto planetary discs ‐ submillimetre.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell