是什么控制了类星体中紫外线到X射线的连续形状？
What controls the UV-to-X-ray continuum shape in quasars?
摘要：
我们提出了一个调查的相互依赖性的光学X射线光谱斜率（$α_{\rm ox}$），HeII等效宽度（EW），和单色光度在2500埃（$L_{2500}$）。$α_{\rm ox}$和HeII EW的值是类星体电离连续体的强度/形状的指标，从紫外线（UV; 1500- 2500埃），通过极紫外线（EUV; 300- 50埃），到X射线（2 keV）制度。对于这项调查，我们测量的HeII EW的206无线电安静类星体没有广泛的吸收线，具有高质量的光谱观测的紫外线和2千电子伏的X射线。样品跨越宽的红移（$\approx$ 0.13--3.5）和光度（log $(L_{2500}$）（$\approx$ 29.2--32.5 erg s $^{-1}$ Hz $^{-1}$）范围。我们恢复了著名的$α_{\rm ox}$ - $L_{2500}$和HeII EW- $L_{2500}$反相关，我们发现$α_{\rm ox}$和HeII EW之间有类似的强相关性，因此从紫外线到极紫外线到X射线的整体光谱形状在很大程度上取决于光度。从每个量中去除$L_{2500}$的贡献后，仍然存在显著的$α_{\rm ox}$-HeII EW相关性，因此EUV和X射线中的发射也直接相关。这组关系是令人惊讶的，因为UV、EUV和X射线发射预期在三个物理上不同的区域中形成。我们的研究结果表明，存在一个红移无关的物理机制，耦合从这三个不同的区域的连续发射，从而控制整体连续的形状从紫外线到X射线制度。
英文摘要：
We present an investigation of the interdependence of the optical-to-X-ray spectral slope ($α_{\rm ox}$), the HeII equivalent-width (EW), and the monochromatic luminosity at 2500 Angstroms ($L_{2500}$). The values of $α_{\rm ox}$ and HeII EW are indicators of the strength/shape of the quasar ionizing continuum, from the ultraviolet (UV; 1500--2500 Angstroms), through the extreme ultraviolet (EUV; 300--50 Angstroms), to the X-ray (2 keV) regime. For this investigation, we measure the HeII EW of 206 radio-quiet quasars devoid of broad absorption lines that have high-quality spectral observations of the UV and 2 keV X-rays. The sample spans wide redshift ($\approx$ 0.13--3.5) and luminosity (log$(L_{2500}$) $\approx$ 29.2--32.5 erg s$^{-1}$ Hz$^{-1}$) ranges. We recover the well-known $α_{\rm ox}$--$L_{2500}$ and HeII EW--$L_{2500}$ anti-correlations, and we find a similarly strong correlation between $α_{\rm ox}$ and HeII EW, and thus the overall spectral shape from the UV, through the EUV, to the X-ray regime is largely set by luminosity. A significant $α_{\rm ox}$--HeII EW correlation remains after removing the contribution of $L_{2500}$ from each quantity, and thus the emission in the EUV and the X-rays are also directly tied. This set of relations is surprising, since the UV, EUV, and X-ray emission are expected to be formed in three physically distinct regions. Our results indicate the presence of a redshift-independent physical mechanism that couples the continuum emission from these three different regions, and thus controls the overall continuum shape from the UV to the X-ray regime.
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