类星体热辐射改正：理论上的考虑
Quasar bolometric corrections: theoretical considerations
摘要：
基于类星体的光-紫外连续光谱的测辐射热校正被广泛用于量化它们的辐射输出，尽管这种估计受到无数不确定性的影响，例如通常未知的中心引擎的视线角度。为了阐明这些问题，我们调查的国家的最先进的模型Hubeny等人。描述薄吸积盘的连续谱，并包括相对论效应。我们探讨了热辐射修正作为质量吸积率，黑洞质量和视角的函数，限制在1型类星体预期的参数空间。我们发现，非线性关系log L_bol=A + B log（λ L_lambda），其中B<=0.9是有利的模型，并变得更紧密的波长减小。我们从模型中计算出对应于波长λ = 1450 A、3000 A和5100 A的测辐射热修正。特别地，对于λ = 3000 A，我们发现A=9.24 +- 0.77和B=0.81 +- 0.02。我们证明了在利用“大蓝凸”光谱积分法测定类星体的L_bol时，由于类星体各向同性发射的假设，可能会导致严重的系统误差。对于一个典型的视角~30度的类星体中心发动机，我们得到的值的L_bol产生的各向同性假设有一个系统误差~30%的高相比，L_bol的值，其中包括吸积盘的各向异性发射。这些结果与观测测定类星体的辐射热光度直接相关，并可用于改进这种估计。
英文摘要：
Bolometric corrections based on the optical-to-ultraviolet continuum spectrum of quasars are widely used to quantify their radiative output, although such estimates are affected by a myriad of uncertainties, such as the generally unknown line-of-sight angle to the central engine. In order to shed light on these issues, we investigate the state-of-the-art models of Hubeny et al. that describe the continuum spectrum of thin accretion discs and include relativistic effects. We explore the bolometric corrections as a function of mass accretion rates, black hole masses and viewing angles, restricted to the parameter space expected for type-1 quasars. We find that a nonlinear relationship log L_bol=A + B log(lambda L_lambda) with B<=0.9 is favoured by the models and becomes tighter as the wavelength decreases. We calculate from the model the bolometric corrections corresponding to the wavelengths lambda = 1450A, 3000A and 5100A. In particular, for lambda=3000A we find A=9.24 +- 0.77 and B=0.81 +- 0.02. We demonstrate that the often-made assumption that quasars emit isotropically may lead to severe systematic errors in the determination of L_bol, when using the method of integrating the "big blue bump" spectrum. For a typical viewing angle of ~30 degrees to the quasar central engine, we obtain that the value of L_bol resulting from the isotropy assumption has a systematic error of ~30% high compared to the value of L_bol which incorporates the anisotropic emission of the accretion disc. These results are of direct relevance to observational determinations of the bolometric luminosities of quasars, and may be used to improve such estimates.
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