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arXiv 1111.6747astro-ph.CO
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银河系外背景光的分光光度测量

Spectrophotometric measurement of the Extragalacic Background Light

Kalevi Mattila, Kimmo Lehtinen, Petri Vaisanen, Gerhard von Appen-Schnur, Christoph Leinert

摘要:

河外背景光(EBL)的紫外、可见和近红外波长由所有未分辨星系沿视线的积分光加上星系际物质(包括假设的衰变遗迹粒子)的任何贡献组成。EBL的测量已被证明是一个繁琐的问题。这是因为夜空亮度的前景分量比EBL本身大得多:黄道光(ZL),综合星光(ISL),漫射银河光(DGL),以及地面观测的气辉(AGL)和对流层散射光。我们一直在开发一种方法,利用屏蔽效应的暗星云的EBL的EBL测量。对高纬度暗星云及其周围区域方向的差分测量提供了仅由两个分量产生的信号,即EBL和来自云的漫散射ISL。我们提出了一个进展报告,这种方法,我们现在利用中间分辨率光谱与ESO的VLT望远镜。我们检测和去除散射ISL成分,利用其特征夫琅和费线光谱签名。与ISL相反,在EBL光谱中,所有谱线都被洗掉。我们提出了一个高质量的光谱,代表我们的目标云和云周围的几个明确的OFF位置之间的差异不透明的位置。我们得出了一个初步的EBL值在400 nm和上限的EBL在520 nm。这些值与从星系计数中得出的EBL下限在同一范围内。

英文摘要:

The Extragalactic Background Light (EBL) at UV, optical and NIR wavelengths consists of the integrated light of all unresolved galaxies along the line of sight plus any contributions by intergalactic matter including hypothetical decaying relic particles. The measurement of the EBL has turned out to be a tedious problem. This is because of the foreground components of the night sky brightness, much larger than the EBL itself: the Zodiacal Light (ZL), Integrated Starlight (ISL), Diffuse Galactic Light (DGL) and, for ground-based observations, the Airglow (AGL) and the tropospheric scattered light. We have been developing a method for the EBL measurement which utilises the screening effect of a dark nebula on the EBL. A differential measurement in the direction of a high-latitude dark nebula and its surrounding area provides a signal that is due to two components only, i.e. the EBL and the diffusely scattered ISL from the cloud. We present a progress report of this method where we are now utilising intermediate resolution spectroscopy with ESO's VLT telescope. We detect and remove the scattered ISL component by using its characteristic Fraunhofer line spectral signature. In contrast to the ISL, in the EBL spectrum all spectral lines are washed out. We present a high quality spectrum representing the difference between an opaque position within our target cloud and several clear OFF positions around the cloud. We derive a preliminary EBL value at 400 nm and an upper limit to the EBL at 520 nm. These values are in the same range as the EBL lower limits derived from galaxy counts.

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