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arXiv 0906.2227astro-ph.SRastro-ph.EP
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前主序星周盘的结构和演化

Structure and evolution of pre-main sequence circumstellar disks

Andrea Isella, John M. Carpenter, Anneila I. Sargent

备注：
Accepted for publication in The Astrophysical Journal, 43 pages, 18 figures, Typo in the author name corrected
发表信息：
Astrophys.J.701:260-282,2009
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摘要：

我们提出了新的亚弧秒（0.7“）毫米波天文学研究组合阵列（CARMA）的1.3毫米连续辐射的观测从11个低和中等质量的前主序星周围的星周盘。从文献中获得了另外3个源的高分辨率观测结果。在所有情况下，盘发射是空间分辨的。我们采用了一个自洽的吸积盘模型，基于盘表面密度的相似解，并将尘埃径向密度分布约束在约40 AU的空间尺度上。盘表面密度似乎与恒星年龄相关，其中特征盘半径在约5百万年内从约20 AU增加到100 AU。这种盘膨胀伴随着质量吸积率的降低，这表明我们的样本盘形成了一个进化序列。根据粘性$α$盘的时间演化解释我们的结果，我们估计：（i）在盘演化的开始，大约60%的星周物质位于25- 40 AU的半径内，（ii）盘形成的质量为0.05 - 0.4 M $_{\sun}$，（iii）盘初始半径处的粘性时标约为0.1-0.3 Myr。粘性盘模型将表面密度$Σ(R)$与盘粘性的径向分布$ν(R) \propto R^γ$紧密联系起来。我们发现$γ$的值范围从-0.8至0.8，这表明粘度对轨道半径的依赖性可以是非常不同的，在所观察到的磁盘。采用$α$参数化的粘度，我们认为，$α$必须减少与轨道半径，它可以在0.5和$10^{-4}$之间变化。（节略）

英文摘要：

We present new sub-arcsecond (0.7'') Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of the 1.3 mm continuum emission from circumstellar disks around 11 low and intermediate mass pre-main sequence stars. High resolution observations for 3 additional sources were obtained from literature. In all cases the disk emission is spatially resolved. We adopt a self consistent accretion disk model based on the similarity solution for the disk surface density and constrain the dust radial density distribution on spatial scales of about 40 AU. Disk surface densities appear to be correlated with the stellar ages where the characteristic disk radius increases from ~ 20 AU to 100 AU over about 5 Myr. This disk expansion is accompanied by a decrease in the mass accretion rate, suggesting that our sample disks form an evolutionary sequence. Interpreting our results in terms of the temporal evolution of a viscous $α$-disk, we estimate (i) that at the beginning of the disk evolution about 60% of the circumstellar material was located inside radii of 25--40 AU, (ii) that disks formed with masses from 0.05 to 0.4 M$_{\sun}$ and (iii) that the viscous timescale at the disk initial radius is about 0.1-0.3 Myr. Viscous disk models tightly link the surface density $Σ(R)$ with the radial profile of the disk viscosity $ν(R) \propto R^γ$. We find values of $γ$ ranging from -0.8 to 0.8, suggesting that the viscosity dependence on the orbital radius can be very different in the observed disks. Adopting the $α$ parameterization for the viscosity, we argue that $α$ must decrease with the orbital radius and that it may vary between 0.5 and $10^{-4}$. (abridged)

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