FAR-ULTRAVIOLET H2 EMISSION FROM CIRCUMSTELLAR DISKS
FAR-ULTRAVIOLET H2 EMISSION FROM CIRCUMSTELLAR DISKS
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DOI：
10.1088/0004-637x/703/2/l137
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发表时间：
2009-09
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通讯作者：
L. Ingleby;N. Calvet;E. Bergin;Ashwin Yerasi;C. Espaillat;G. Herczeg;È. Roueff;H. Abgrall;J. Hernández;C. Briceño;I. Pascucci;Jonathan M. Miller;J. Fogel;L. Hartmann;M. Meyer;J. Carpenter;N. Crockett;M. McClure
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作者：
L. Ingleby;N. Calvet;E. Bergin;Ashwin Yerasi;C. Espaillat;G. Herczeg;È. Roueff;H. Abgrall;J. Hernández;C. Briceño;I. Pascucci;Jonathan M. Miller;J. Fogel;L. Hartmann;M. Meyer;J. Carpenter;N. Crockett;M. McClure
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。其中28个来源于1000万年前的金牛座-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，1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FUV光谱中的一个功能，主要是由于电子碰撞激发的H2来研究内部磁盘中的气体的演变。我们发现H2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，而这些辐射能够激发出盘内的H2，因此非吸积源没有H2辐射的事实意味着内盘内的H2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。使用1600埃的通量，我们估计留在我们样本中碎片盘内部区域的H2柱密度小于103 × 10−6 g cm-2，比1 Au的最小质量太阳星云的表面密度低9个数量级。
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 1, 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 ∼3 × 10−6 g cm-2, 9 orders of magnitude below the surface density of the minimum mass solar nebula at 1 AU.