In observations of diffuse emissions like, e.g., the Lyman-$\alpha$ 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.

中文翻译：

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推断未解析点源对紫外线天空调查中测量的漫射辐射的贡献：通用方法和 SOHO/SWAN 案例研究

在对漫射发射（例如 Lyman-$\alpha$ 日光层辉光）的观测中，对来自点源（例如恒星）的观测信号的贡献被视为污染。通常可以正确解析并且可以减去或屏蔽的最亮点源相对较少。我们使用来自 SOHO/SWAN 仪器的紫外线天空测量图和来自 IUE 卫星的分光光度计数据来展示点源分布的分析结果。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，这些源无法根据来自反向散射辉光的漫射信号进行解析，从而导致来自未解析点源的特定物理背景。检测，对点源背景的理解和减法对正确表征扩散排放和与模型的准确比较有影响。恒星也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很重要。我们提出了一种通用方法来量化来自紫外线天空测量图中未解析点源的背景辐射水平。在所提出的方法中，点源的分布作为其强度的函数被适当地积分以计算背景信号水平。这些一般考虑因素用于估计 SOHO/SWAN 观测中未解析的点源背景，平均为 $28.9$R。