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arXiv 0909.0688astro-ph.SR
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星周星云的远紫外H2辐射

Far-Ultraviolet H2 Emission from Circumstellar Disks

Laura Ingleby, Nuria Calvet, Edwin Bergin, Ashwin Yerasi, Catherine Espaillat, Gregory Herczeg, Evelyne Roueff, Herve Abgrall, Jesus Hernandez, Cesar Briceno, I… 展开作者

Laura Ingleby, Nuria Calvet, Edwin Bergin, Ashwin Yerasi, Catherine Espaillat, Gregory Herczeg, Evelyne Roueff, Herve Abgrall, Jesus Hernandez, Cesar Briceno, Ilaria Pascucci, Jon Miller, Jeffrey Fogel, Lee Hartmann, Michael Meyer, John Carpenter, Nathan Crockett, Melissa McClure

备注：
15 pages, 4 figures, accepted to ApJL
发表信息：
Astrophys.J.703:L137-L141,2009
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摘要：

我们分析了33个经典金牛座T星（CTTS）的远紫外（FUV）光谱，其中包括20个新的光谱与先进的相机测量太阳盲通道（ACS/SBC）的哈勃太空望远镜。在这些来源中，28个来源于约100万年前的金牛座-御夫座复合体或猎户座分子云，4个来源于8- 1000万年前的猎户座OB 1a复合体，一个来源于1000万年前的TW Hydrae协会。我们还获得了FUV ACS/SBC光谱的10个非吸积源周围的碎片盘的年龄在10和125万年之间。我们使用的功能，主要是由于电子碰撞激发的\h 2的FUV光谱研究的演化的气体在内部磁盘。我们发现\h 2特征在非吸积源中不存在，但在CTTS的光谱中被检测到，并且与吸积光度相关。由于所有的年轻恒星都有活跃的色球层，这些色球层会产生强烈的X射线和紫外线辐射，能够激发盘内的\h 2，所以非吸积源没有显示出\h 2辐射，这意味着内盘中的\h 2气体已经在非吸积源中消散，尽管尘埃（可能还有气体）仍然存在于更大的半径。利用1600埃的通量，我们估计留在样本碎片盘内部区域的\h 2的柱密度小于~ 3 × 10 ^-6 g cm^-2，比1天文单位处最小质量太阳星云的表面密度低9个数量级。

英文摘要：

We analyze the far-ultraviolet (FUV) spectra of 33 classical T Tauri stars (CTTS), including 20 new spectra obtained with the Advanced Camera for Surveys Solar Blind Channel (ACS/SBC) on the Hubble Space Telescope. Of the sources, 28 are in the ~1 Myr old Taurus-Auriga complex or Orion Molecular Cloud, 4 in the 8-10 Myr old Orion OB1a complex and one, TW Hya, in the 10 Myr old TW Hydrae Association. We also obtained FUV ACS/SBC spectra of 10 non-accreting sources surrounded by debris disks with ages between 10 and 125 Myr. We use a feature in the FUV spectra due mostly to electron impact excitation of \h2 to study the evolution of the gas in the inner disk. We find that the \h2 feature is absent in non-accreting sources, but is detected in the spectra of CTTS and correlates with accretion luminosity. Since all young stars have active chromospheres which produce strong X-ray and UV emission capable of exciting \h2 in the disk, the fact that the non-accreting sources show no \h2 emission implies that the \h2 gas in the inner disk has dissipated in the non-accreting sources, although dust (and possibly gas) remains at larger radii. Using the flux at 1600 Å, we estimate that the column density of \h2 left in the inner regions of the debris disks in our sample is less than ~ 3x10^-6 g cm^-2, nine orders of magnitude below the surface density of the minimum mass solar nebula at 1 AU.

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