arXiv 0710.18342007-10astro-ph

在CTTS LkHa 264和碎片盘49 Cet中寻找NIR分子氢发射

A Search for NIR Molecular Hydrogen Emission in the CTTS LkHa 264 and the debris disk 49 Cet

A. Carmona, M. E van den Ancker, Th. Henning, M. Goto, D. Fedele, B. Stecklum

备注：: Accepted by A&A 9 October 2007 11 pages, 4 figures. v2: typo in the second author affilitiation for the astroph abstract was corrected. No changes in the main article. v3, v4: typo in Sect 2., Sect. 4.2. corrected. v5: typo in Table 4. corrected, Fig. 3. updated
DOI：: 10.1051/0004-6361:20078536e

摘要：

我们报告的第一个结果的搜索H2排放的原行星盘使用CRIRES，ESO的新的VLT高分辨率近红外光谱仪。我们观测了CTTS LkHa 264和碎片盘49 Cet，并搜索了1-0 S（1），1-0 S（0）和2-1 S（1）H2发射线。在LkHa 264中检测到2.1218微米处的H2线。我们的CRIRES光谱揭示了先前在LkHa 264中在2.2233微米处观察到但未检测到的H2线。导出了LkH α 264中2-1 S（1）H2线通量的上限。这些观测是首次同时探测到原行星盘的1-0 S（1）和1-0 S（0）H2辐射。49 Cet在三条观察到的谱线中的任何一条中都没有表现出H2发射。在LkHa 264的内盘（约0.1天文单位）中，有一些月球质量的光学薄的热H2，而在49 Cet的内盘中，热H2的质量不到月球质量的十分之一。在LkHa 264中测得的1-0 S（0）/1-0 S（1）和2-1 S（1）/1-0 S（1）线比表明，H2发射气体的温度<1500 K，并且H2最有可能被UV光子热激发。线的形状的建模表明，盘应该被看到接近正面（i<35）。对探测到和未探测到H2 1-0 S（1）线的CTTS的物理性质的比较分析表明，H2发射的存在与UV过量的大小和H α线的强度相关。Cet 49的近红外光谱中没有H2发射，也没有Halpha发射，这表明Cet 49内盘中的气体已经消散。围绕Cet 49的圆盘应该有一个内孔。

英文摘要：

We report on the first results of a search for H2 emission from protoplanetary disks using CRIRES, ESO's new VLT high resolution NIR spectrograph. We observed the CTTS LkHa 264 and the debris disk 49 Cet, and searched for the 1-0 S(1), 1-0 S(0) and 2-1 S(1) H2 emission lines. The H2 line at 2.1218 micron is detected in LkHa 264. Our CRIRES spectra reveal the previously observed but not detected H2 line at 2.2233 micron in LkHa 264. An upper limit on the 2-1 S(1) H2 line flux in LkHalpha 264 is derived. These observations are the first simultaneous detection of 1-0 S(1) and 1-0 S(0) H2 emission from a protoplanetary disk. 49 Cet does not exhibit H2 emission in any of the three observed lines. There are a few lunar masses of optically thin hot H2 in the inner disk (~0.1 AU) of LkHa 264, and less than a tenth of a lunar mass of hot H2 in the inner disk of 49 Cet. The measured 1-0 S(0)/1-0 S(1) and 2-1 S(1)/1-0 S(1) line ratios in LkHa 264 indicate that the H2 emitting gas is at T<1500 K and that the H2 is most likely thermally excited by UV photons. Modeling of the shape of the line suggests that the disk should be seen close to face-on (i<35). A comparative analysis of the physical properties of CTTS in which the H2 1-0 S(1) line has been detected and non-detected indicates that the presence of H2 emission is correlated with the magnitude of the UV excess and the strength of the Halpha line. The lack of H2 emission in the NIR spectra of 49 Cet and the absence of Halpha emission suggest that the gas in the inner disk of 49 Cet has dissipated. The disk surrounding 49 Cet should have an inner hole.

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