推知UV巡天中未分辨点源对散射辐射的贡献：一般方法和SOHO/SWAN个例研究
Inferring contributions from unresolved point sources to diffuse emissions measured in UV sky surveys: general method and SOHO/SWAN case study
摘要：
在对扩散发射的观测中，例如，莱曼- $α$日光层辉光，对来自点源的观测信号的贡献（例如，星）被视为污染。有相对较少的最亮点源，通常是正确解决，可以减去或屏蔽。我们目前的点源分布的分析结果，使用SOHO/SWAN仪器和分光光度计数据从IUE卫星的紫外巡天图。估计的分布表明，这些来源的数量随着强度的降低而增加。低于某个阈值，这些源不能相对于来自后向散射辉光的漫射信号被分辨，这导致来自未分辨的点源的某个物理背景。点源背景的检测、理解和扣除对扩散排放的适当表征和与模型的准确比较具有影响。恒星还经常被用作卫星紫外线观测飞行校准的标准烛光，因此正确理解点源的信号贡献对于校准过程非常重要。我们提出了一个通用的方法来量化的背景辐射水平，从未解决的点源在紫外巡天地图。在所提出的方法中，作为其强度的函数的点源的分布被适当地积分以计算背景信号水平。这些一般的考虑被应用于估计SOHO/SWAN观测中未分辨的点源背景，其平均值为$28.9$ R。我们还讨论了背景辐射的各向异性和一般问题有关的建模点源的贡献扩散紫外线发射观测。
英文摘要：
In observations of diffuse emissions like, e.g., the Lyman-$α$ heliospheric glow, contributions to the observed signal from point sources (e.g., stars) are considered as a contamination. There are relatively few brightest point sources that are usually properly resolved and can be subtracted or masked. We present results of analysis of the distribution of point sources using UV sky-survey maps from the SOHO/SWAN instrument and spectrophotometry data from the IUE satellite. The estimated distribution suggests that the number of these sources increases with decreasing intensity. Below a certain threshold, these sources cannot be resolved against the diffuse signal from the backscatter glow, that results in a certain physical background from unresolved point sources. Detection, understanding and subtraction of the point-source background has implications for proper characterization of diffuse emissions and accurate comparison with models. Stars are also often used as standard candles for in-flight calibration of satellite UV observations, thus proper understanding of signal contributions from the point sources is important for the calibration process. We present a general approach to quantify the background radiation level from unresolved point sources in UV sky-survey maps. In the proposed method, a distribution of point sources as a function of their intensity is properly integrated to compute the background signal level. These general considerations are applied to estimate the unresolved-point-sources background in the SOHO/SWAN observations that on average amounts to $28.9$ R. We discuss also the background radiation anisotropies and general questions related to modeling the point-source contributions to diffuse UV-emission observations.
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