M-BAND SPECTRA OF DUST-EMBEDDED SOURCES AT THE GALACTIC CENTER
M-BAND SPECTRA OF DUST-EMBEDDED SOURCES AT THE GALACTIC CENTER
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银河系中心尘埃嵌入源的 M 波段光谱
DOI：
10.1088/0004-637x/703/2/1635
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
R. Schödel
中科院分区：
文献类型：
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作者：
J. Moultaka;A. Eckart;R. Schödel
本文的目的是研究银河系中央星团中最亮的尘埃覆盖源周围的星周物质。观测工作是在智利帕拉纳尔的欧洲南方天文台甚大望远镜（VLT）上进行的。我们在 VLT 上使用 ISAAC 相机的长波长 (LWS3) 低分辨率 (LR) 光谱模式，M 滤光片的光谱范围为 4.4 μm 至 5.1 μm。使用 0.''6 的狭缝宽度意味着光谱分辨率为 R = λ/Δλ = 800 (Δv = 375 km s−1)。这些观测结果得出了银河系中央星团中 15 个亮源的 M 波段光谱。除了气态 12CO (4.666 μm) 和 13CO (4.77 μm) 振动旋转吸收之外，我们还检测到由于极性和非极性 CO 冰的混合物（中心位于 4.675 μm）而产生的强吸收。在较短波长的吸收翼中，4.62 μm 处的 XCN 具有吸收特征。 XCN 吸收对 M2 超巨星 IRS 7 最强。我们发现，由于 CO 冰和 CO 气体吸收所追踪的物质引起的灭绝可能具有相当的重要性。使用 IRS 2L 和 IRS 16C 的光谱，我们对 CO 冰和 13CO 气体造成的视线吸收进行一阶校正。结合已发表的亚毫米 CO(7–6) 和 FIR [O i] 线数据的氢数密度估计，我们获得了 10−3 和 10−2 M☉ 量级的星周壳层气体质量。这意味着，在未来以高光谱和角分辨率拍摄的光谱中，由于源固有吸收，明亮且嵌入尘埃的银河中心源应显示出大量的线吸收。
The goal of the present paper is to investigate the circumstellar material around the brightest dust-enshrouded sources in the central stellar cluster of the Milky Way. Observations have been carried out at the European Southern Observatory's Very Large Telescope (VLT) on Paranal, Chile. We have used the long wavelength (LWS3) low resolution (LR) spectroscopic mode of the ISAAC camera at the VLT in the spectral range of the M filter from 4.4 μm to 5.1 μm. The use of a slit width of 0.″6 implied a spectral resolution of R = λ/Δλ = 800 (Δv = 375 km s−1). These observations resulted in the M-band spectra of 15 bright sources in the central stellar cluster of the Milky Way. In addition to gaseous 12CO (4.666 μm) and 13CO (4.77 μm) vibration-rotational absorptions, we detect a strong absorption due to a mixture of polar and apolar CO ice (centered at 4.675 μm). In the shorter wavelength absorption wing there is an absorption feature due to XCN at 4.62 μm. The XCN absorption is strongest toward the M2 supergiant IRS 7. We find that the extinctions due to material traced by the CO ice and the CO gas absorptions may be of comparable importance. Using the spectra of IRS 2L and IRS 16C, we perform a first order correction of the line-of-sight absorption due to CO ice and 13CO gas. In combination with published hydrogen number density estimates from sub-millimeter CO(7–6) and FIR [O i] line data, we obtain gas masses of the circumstellar shells of the order of 10−3 and 10−2 M☉. This implies that in future spectra taken at high spectral and angular resolution the bright and dust-embedded Galactic center sources should show a substantial line absorption due to source intrinsic absorption.