Detection of an Inner Gaseous Component in a Herbig Be Star Accretion Disk: Near- and Mid-Infrared Spectrointerferometry and Radiative Transfer modeling of MWC 147
Detection of an Inner Gaseous Component in a Herbig Be Star Accretion Disk: Near- and Mid-Infrared Spectrointerferometry and Radiative Transfer modeling of MWC 147
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Herbig Be 恒星吸积盘中内部气体成分的检测：近红外和中红外光谱干涉测量以及 MWC 147 的辐射传输建模
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发表时间：
2007
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通讯作者：
K. Ohnaka
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作者：
S. Kraus;T. Preibisch;K. Ohnaka
利用近红外（NIR）K波段VLTI/AMBER观测数据、PTI存档数据以及中红外（MIR）N波段VLTI/AMBER观测数据，研究了Herbig Be星星MWC 147周围星周区域的几何和物理条件。MWC 147的发射清晰可辨，在2.2和11 μm处的特征物理尺寸分别为~1.3和~9 Au（高斯直径）。MIR发射揭示了与在中等倾角下看到的盘结构一致的不对称性。光谱分散的琥珀色和琥珀色的干涉图都显示出强烈的增加，在特征尺寸向更长的波长，更陡峭的比预测的分析磁盘模型假设幂律径向温度分布。我们模型的干涉数据和光谱能量分布的MWC 147与二维，频率相关的辐射传输模拟。这个分析表明，球面包络或被动辐射开普勒磁盘（垂直或弯曲的膨胀的内缘）的模型可以很容易地适应SED，但预测比观察到的低得多的vibrations;这种模型预测的角度大小是2-4倍的大小来自干涉数据，所以这些模型可以明确地排除。然而，模型的开普勒光盘光学厚气体排放从一个活跃的气体盘（尘埃升华区内），产生一个很好的拟合的SED，并同时再现的绝对水平和光谱依赖的近红外和中红外光谱。我们的结论是，近红外连续发射MWC 147的吸积光度占主导地位的光学厚的内部气体盘出现，而MIR发射也包含来自外部的贡献，照射尘埃盘。
We study the geometry and the physical conditions in the inner (AU-scale) circumstellar region around the young Herbig Be star MWC 147 using long-baseline spectrointerferometry in the near-infrared (NIR) K-band, VLTI/AMBER observations, and PTI archive data, as well as the mid-infrared (MIR) N-band, VLTI/MIDI observations. The emission from MWC 147 is clearly resolved and has a characteristic physical size of ~1.3 and ~9 AU at 2.2 and 11 μm, respectively (Gaussian diameter). The MIR emission reveals asymmetry consistent with a disk structure seen under intermediate inclination. The spectrally dispersed AMBER and MIDI interferograms both show a strong increase in the characteristic size toward longer wavelengths, much steeper than predicted by analytic disk models assuming power-law radial temperature distributions. We model the interferometric data and the spectral energy distribution of MWC 147 with two-dimensional, frequency-dependent radiation transfer simulations. This analysis shows that models of spherical envelopes or passive irradiated Keplerian disks (with vertical or curved puffed-up inner rim) can easily fit the SED, but predict much lower visibilities than observed; the angular size predicted by such models is 2-4 times larger than the size derived from the interferometric data, so these models can clearly be ruled out. Models of a Keplerian disk with optically thick gas emission from an active gaseous disk (inside the dust sublimation zone), however, yield a good fit of the SED and simultaneously reproduce the absolute level and the spectral dependence of the NIR and MIR visibilities. We conclude that the NIR continuum emission from MWC 147 is dominated by accretion luminosity emerging from an optically thick inner gaseous disk, while the MIR emission also contains contributions from the outer, irradiated dust disk.