THE OPTX PROJECT. III. X-RAY VERSUS OPTICAL SPECTRAL TYPE FOR ACTIVE GALACTIC NUCLEI
THE OPTX PROJECT. III. X-RAY VERSUS OPTICAL SPECTRAL TYPE FOR ACTIVE GALACTIC NUCLEI
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OPTX 项目。
DOI：
10.1088/0004-637x/703/2/2160
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
R. Mushotzky
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文献类型：
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作者：
L. Trouille;A. Barger;L. Cowie;Y. Yang;R. Mushotzky
我们比较了在钱德拉三个场（CLANS、CLASXS和CDF-N）覆盖~ 1.2度2的均匀选择（通量大于3σ水平且通量极限为f2-8 keV >.5 × 10 - 15 erg cm - 2 s - 1以上的源）、高度光谱完整（f2-8 keV >0 - 14 erg cm - 2 s - 1的>80%,>60%以下）2 - 8 keV x射线样品的光谱类型和x射线光谱性质。对于我们的645个光谱观测源的样本，我们证实了不同光谱类型的有效光子指数Γeff（由0.5-2 keV与2-8 keV计数的比率获得）所确定的x射线光谱特性有显著的重叠。例如，宽线活动星系核（agn）预计不会被遮挡，因此x射线软（Γeff小于1.2），但我们发现20%±3%的人Γeff <1.2。非宽线agn预计会被遮挡，因此x射线很难（Γeff < 1.2），但我们发现33%±4%的agn具有Γeff大于或等于1.2。因此，不能将x射线光谱分类与光学光谱分类等同使用。由于不了解x射线和光学分类与中央发动机遮挡的关系，我们强烈建议反对混合分类方案，因为它只会使x射线AGN样品的解释复杂化。我们证实了光谱类型与x射线光度的相关性，当z < 1时，我们发现了类似的Γeff光度相关性。然而，由于Γeff高度依赖红移的特性，这种依赖关系在更高的红移处失效。因此，我们也提醒任何依赖Γeff的分类方案都可能遭受严重的红移偏差。
We compare the optical spectral types with the X-ray spectral properties for a uniformly selected (sources with fluxes greater than the 3σ level and above a flux limit of f2–8 keV > 3.5 × 10−15 erg cm−2 s−1), highly spectroscopically complete (>80% for f2–8 keV > 10−14 erg cm−2 s−1 and >60% below) 2–8 keV X-ray sample observed in three Chandra fields (CLANS, CLASXS, and the CDF-N) that cover ∼1.2 deg2. For our sample of 645 spectroscopically observed sources, we confirm that there is significant overlap of the X-ray spectral properties, as determined by the effective photon indices, Γeff, obtained from the ratios of the 0.5–2 keV to 2–8 keV counts, for the different optical spectral types. For example, broad-line active galactic nuclei (AGNs) are expected to be unobscured and hence X-ray soft (Γeff ⩾ 1.2), yet we find 20%± 3% have Γeff <1.2. Non-broad-line AGNs are expected to be obscured and hence X-ray hard (Γeff < 1.2), yet we find 33% ± 4% have Γeff ⩾ 1.2. Thus, one cannot use the X-ray spectral classifications and the optical spectral classifications equivalently. Since it is not understood how X-ray and optical classifications relate to the obscuration of the central engine, we strongly advise against a mixed classification scheme, as it can only complicate the interpretation of X-ray AGN samples. We confirm the dependence of optical spectral type on X-ray luminosity, and for z < 1, we find a similar luminosity dependence of Γeff. However, this dependence breaks down at higher redshifts due to the highly redshift-dependent nature of Γeff. We therefore also caution that any classification scheme which depends on Γeff is likely to suffer from serious redshift bias.
C.A.诺曼：《天体物理学杂志》。
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