AGN Reddening and Ultraviolet Extinction Curves from Hubble Space Telescope Spectra
AGN Reddening and Ultraviolet Extinction Curves from Hubble Space Telescope Spectra
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发表时间：
2007-11
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通讯作者：
C. Gaskell;A. J. Benker
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作者：
C. Gaskell;A. J. Benker
给出了14个活动星系核的内禀消光曲线。活动星系核的红化，E（B-V），高达0.36马格。大多数（13出14）的消光曲线是不陡峭的紫外线。在七条最佳消光曲线中，有五条在光学和近紫外线下的消光曲线与标准银河系曲线一样平坦，但在远紫外线下更平坦，并且没有2175埃的特征。其中一个活动星系核B3 0754+394具有陡峭的SMC样消光曲线，另一个活动星系核Mrk 304具有LMC样消光曲线，可能包括2175 Ang。碰一下。剩下的七个较低质量的消光曲线具有与LMC状形状或平坦形状一致的整体形状。两个可能有2175个特征，一个可能与银河系曲线相同。在我们确定的最佳消光曲线中占主导地位的平坦曲线并不像Gaskell等人（2004）的射电强活动星系核消光曲线那样平坦。这表明，由于复合光谱中的光度依赖性红化偏差，先前的射电消光曲线在4 < 1/lambda < 6.5倒数微米的范围内可能稍微太平坦，但需要进一步的研究。我们提出了一个参数化的平均活动星系核消光曲线。观测到的活动星系核的连续特性的变化是不一致的内在对象到对象的变化，因为观测到的差异是最小的吸积盘光谱的变化应该是最大的远紫外。我们认为，莱曼α附近活动星系核光谱的陡峭化是少量SMC类尘埃（E（B-V）~ 0.03）的结果。我们发现最大的对象到对象的光谱形状的差异是在Fe II发射的“蓝色小肿块”。
We present intrinsic extinction curves for 14 AGNs. The AGNs have reddenings, E(B-V), of up to 0.36 mag. The majority (13 out of 14) of the extinction curves are not steep in the UV. Of the seven best determined extinction curves, five have extinction curves that are as flat as the standard Galactic curve in the optical and near UV, but flatter in the far UV, and without the 2175 Angstrom feature. One AGN, B3 0754+394, has a steep SMC-like extinction curve, and another, Mrk 304, has an LMC-like extinction curve, including a probable 2175 Ang. bump. The remaining seven, lower-quality, extinction curves have overall shapes that are consistent with an LMC-like shape or a flatter shape. Two have possible 2175 features, and one might be identical to the Galactic curve. The flatter curves that predominate in our best determined extinction curves are not as flat as the Gaskell et al. (2004) extinction curve for radio-loud AGNs. This suggests that the previous radio-loud extinction curve might be slightly too flat in the range 4 < 1/lambda < 6.5 inverse microns because of luminosity-dependent reddening biases in the composite spectra, but further investigation is needed. We present a parameterized average AGN extinction curve. Observed variations in the continuum properties of the AGNs are inconsistent with intrinsic object-to-object variations because observed differences are least in the far UV where changes in the accretion disk spectrum should be greatest. We suggest that the steepening of AGN spectra around Lyman alpha is the result of a small amount of SMC-like dust (E(B-V) ~ 0.03). We find the largest object-to-object differences in spectral shape to be in the Fe II emission of the "small blue bump".