类星体Ton 34不寻常的UV连续谱和晶体尘埃吸收的可能性
The unusual UV continuum of quasar Ton 34 and the possibility of crystalline dust absorption
摘要：
已知发光类星体在1100 A附近的连续谱会急剧变陡。这种光谱特征不能很好地拟合当前的吸积盘模型，除非光盘发射的康普顿调用。已提出碳结晶粉尘的吸收来解释这一特征。Ton 34（z=1.928）是Telfer等分析的183个类星体HST-FOS光谱中远紫外衰减最陡的（F_nuprop_nu^{-5.3}），它是检验晶体尘埃假说和紫外突变的其他解释的理想天体。结合HST、IUE和Palomar光谱，我们重建了Ton 34的紫外光谱能量分布。远紫外线连续谱显示出一个非常深的连续谱槽，其边界是一个陡峭的远紫外线上升。我们假设是纳米金刚石尘埃。碳结晶尘埃的消光相当好地再现了Ton 34的深吸收槽，但没有观察到极端紫外线的急剧上升。我们还研究了一个内在的连续翻转的可能性。尘埃可能是高速外流（13000 km/s）的一部分，在CIV，OVI，NV和Ly_alpha谱线上可以观测到。
英文摘要：
Luminous quasars are known to display a sharp steepening of the continuum near 1100A. This spectral feature is not well fitted by current accretion disk models, unless comptonization of the disk emission is invoked. Absorption by carbon crystalline dust has been proposed to account for this feature. Ton 34 (z=1.928) exhibits the steepest far-UV decline (F_nu prop nu^{-5.3}) among the 183 quasar HST-FOS spectra analyzed by Telfer et al. It is an ideal object to test the crystalline dust hypothesis as well as alternative interpretations of the UV break. We reconstruct the UV spectral energy distribution of Ton 34 by combining HST, IUE and Palomar spectra. The far-UV continuum shows a very deep continuum trough, which is bounded by a steep far-UV rise. We fit the trough assuming nanodiamond dust grains. Extinction by carbon crystalline dust reproduces the deep absorption trough of Ton 34 reasonably well, but not the observed steep rise in the extreme UV. We also study the possibility of an intrinsic continuum rollover. The dust might be part of a high velocity outflow (13000 km/s), which is observed in absorption in the lines of CIV, OVI, NV and Ly_alpha.
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