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arXiv 1003.4318astro-ph.SRastro-ph.EP
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研究星周盘中的行星形成:RY Tau和DG Tau的CARMA观测

Investigating planet formation in circumstellar disks: CARMA observations of RY Tau and DG Tau

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

摘要:

本文介绍了年轻恒星RYTau和DGTau周围星周盘在波长为1.3mm和2.8mm处热尘埃辐射的CARMA观测结果。地图的角分辨率高达0.15角秒,或20天文单位的金牛座云的距离,这是一个高出2倍,迄今已取得的这些波长。由此产生的磁盘图像的前所未有的细节使我们能够解决与行星形成有关的三个重要问题。(1)星周尘埃的径向分布是怎样的?(2)尘埃排放是否显示出任何可能表明(原)行星存在的间隙迹象?(3)尘埃的性质取决于轨道半径吗?我们发现,无论是一个经典的幂律或粘性盘演化的相似性解决方案方面的磁盘表面密度建模,再现观测。来自RYTau的1.3毫米图像显示了两个相隔0.2角秒的峰值,尘埃辐射朝着恒星位置下降,这在大约2- 4 sigma处很明显。对于RYTau和DGTau,在半径大于15 AU的尘埃排放显示没有显着偏离未扰动的粘性盘模型。特别地,在灰尘分布中没有检测到径向间隙。在合理的假设下,我们排除了质量超过5个木星质量的行星的存在,这些行星绕着两颗恒星的距离在10到60 AU之间。通过比较1.3mm和2.8mm的观测结果,研究了尘埃不透明度斜率β的径向变化。我们发现DGTau和RYTau的β平均值分别为0.5和0.7。在20和70 AU之间,β的变化小于0.7。这些结果证实了这些星盘中的星周尘埃与星际介质中的尘埃有很大的不同。

英文摘要:

(Abridged) We present CARMA observations of the thermal dust emission from the circumstellar disks around the young stars RYTau and DGTau at wavelengths of 1.3mm and 2.8mm. The angular resolution of the maps is as high as 0.15arcsec, or 20AU at the distance of the Taurus cloud, which is a factor of 2 higher than has been achieved to date at these wavelengths. The unprecedented detail of the resulting disk images enables us to address three important questions related to the formation of planets. (1) What is the radial distribution of the circumstellar dust? (2) Does the dust emission show any indication of gaps that might signify the presence of (proto-)planets? (3) Do the dust properties depend on the orbital radius? We find that modeling the disk surface density in terms of either a classical power law or the similarity solution for viscous disk evolution, reproduces the observations well. The 1.3mm image from RYTau shows two peaks separated by 0.2arcsec with a decline in the dust emission toward the stellar position, which is significant at about 2-4sigma. For both RYTau and DGTau, the dust emission at radii larger than 15 AU displays no significant deviation from an unperturbed viscous disk model. In particular, no radial gaps in the dust distribution are detected. Under reasonable assumptions, we exclude the presence of planets more massive than 5 Jupiter masses orbiting either star at distances between about 10 and 60 AU. The radial variation of the dust opacity slope, beta, was investigated by comparing the 1.3mm and 2.8mm observations. We find mean values of beta of 0.5 and 0.7 for DGTau and RYTau respectively. Variations in beta are smaller than 0.7 between 20 and 70 AU. These results confirm that the circumstellar dust throughout these disks differs significantly from dust in the interstellar medium.

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