论文标题
检测PAH吸收和确定中红外弥漫性星际灭绝曲线从视线向CYG OB2-12
Detection of PAH Absorption and Determination of the Mid-Infrared Diffuse Interstellar Extinction Curve from the Sightline Toward Cyg OB2-12
论文作者
论文摘要
朝向发光的蓝色超级CYG OB2-12的视线被广泛用于研究星际灰尘，这是由于其巨大的灭绝（$ a_v \ simeq 10 $ mag），事实上，这种灭绝似乎是由弥漫性跨体界面媒介典型的粉尘所支配的。我们使用恒星及其恒星风的发射模型对CYG OB2-12的档案ISO-SW和Spitzer IRS观察进行了新的分析，以确定总灭绝$A_λ$从2.4----37 $ $ m $ m。除了突出的9.7和18 $ $ M硅酸盐特征外，我们还可以稳健地检测到与多环芳烃（PAHS）相关的吸收特征，包括首次识别7.7 $ $ $ m的吸收功能。发现3.3 $ $ $ m芳香特征的吸收比发射中所见。观察到3.4和6.85 $ m $ m脂肪烃特征，其相对强度与观察到朝向银河中心的视线上的这些特征一致。我们在此波长范围内识别并表征了六十多个光谱线，这可能在限制恒星及其恒星风的模型中有用。基于此分析，我们提出了一条灭绝曲线$a_λ/a_ {2.2μm} $，该曲线可平稳地推断出较短波长的平均银河灭绝曲线，并从较短波长中推断出的尘埃不相处，并在更长的波长中从发射中推断出对中等限制的星际污染模型的新模型。
The sightline toward the luminous blue hypergiant Cyg OB2-12 is widely used in studying interstellar dust on account of its large extinction ($A_V \simeq 10$ mag) and the fact that this extinction appears to be dominated by dust typical of the diffuse interstellar medium. We present a new analysis of archival ISO-SWS and Spitzer IRS observations of Cyg OB2-12 using a model of the emission from the star and its stellar wind to determine the total extinction $A_λ$ from 2.4--37 $μ$m. In addition to the prominent 9.7 and 18 $μ$m silicate features, we robustly detect absorption features associated with polycyclic aromatic hydrocarbons (PAHs), including the first identification of the 7.7 $μ$m feature in absorption. The 3.3 $μ$m aromatic feature is found to be much broader in absorption than is typically seen in emission. The 3.4 and 6.85 $μ$m aliphatic hydrocarbon features are observed with relative strengths consistent with observation of these features on sightlines toward the Galactic Center. We identify and characterize more than sixty spectral lines in this wavelength range, which may be useful in constraining models of the star and its stellar wind. Based on this analysis, we present an extinction curve $A_λ/A_{2.2 μm}$ that extrapolates smoothly to determinations of the mean Galactic extinction curve at shorter wavelengths and to dust opacities inferred from emission at longer wavelengths, providing a new constraint on models of interstellar dust in the mid-infrared.
