标题： SDSS早期数据发布中的射电宁静类星体的X射线发射。 α_ox 对紫外光度的依赖性 显示英文标题

标题： X-ray emission from radio-quiet quasars in the SDSS Early Data Release. The alpha_ox dependence upon UV luminosity

摘要： 我们利用ROSAT、Chandra和XMM-Newton数据，研究了斯隆数字巡天（SDSS）早期数据发布中的颜色选择的宁静射电类星体（RQQs）的X射线性质。在红移范围0.16到6.28之间，有136个RQQs被X射线探测到（其中69个来自ROSAT全天巡天，RASS），而对于另外70个RQQs则得到了X射线上限值。SDSS所采用的定义明确的选择方法，结合FIRST/NVSS调查施加的严格的射电约束，使我们能够确定一个具有代表性的光学选择的RQQ样本，其宽带谱能量分布（通过光学至X射线光谱指数αox表征）可以作为本征紫外（UV）亮度和红移的函数进行研究。应用于SDSS样本的部分相关性分析（包括上限值，但排除了RASS探测子样本中的偏差）表明αox是本征紫外亮度的函数（即，在高紫外亮度下αox变得更陡峭）；该相关性在3.7σ水平上显著。我们没有检测到αox具有高度显著的红移依赖性。我们还发现了一个显著的（7.8σ水平）UV和X射线亮度之间的相关性。这个由Lx \propto Luv^{0.75+/-0.06}参数化的相关性将先前的结果扩展到了最高的红移范围内。 显示英文摘要

摘要： We investigate the X-ray properties of the color-selected radio-quiet quasars (RQQs) in the Sloan Digital Sky Survey (SDSS) Early Data Release using ROSAT, Chandra, and XMM-Newton data. In the 0.16-6.28 redshift range, 136 RQQs have X-ray detections (69 from the ROSAT All-Sky Survey, RASS), while for 70 RQQs X-ray upper limits are obtained. The well-defined selection method utilized by the SDSS, coupled with the tight radio constraints from the FIRST/NVSS surveys, allow us to define a representative sample of optically selected RQQs whose broad-band spectral energy distributions (characterized by means of the optical-to-X-ray spectral index, alpha_ox) can be studied as a function of rest-frame ultraviolet (UV) luminosity and redshift. A partial correlation analysis applied to the SDSS sample (including the upper limits, but excluding the biased subsample of RASS detections) shows that alpha_ox is a function of rest-frame UV luminosity (i.e., alpha_ox steepens at high UV luminosities); this correlation is significant at the 3.7 sigma level. We do not detect a highly significant redshift dependence of alpha_ox. We also find a significant (7.8 sigma level) correlation between UV and X-ray luminosity. This correlation, parameterized by Lx \propto Luv^{0.75+/-0.06}, extends previous results to the highest redshifts.