盘状星系周围弥散星晕光的点扩散函数尾和测量
Point spread function tails and the measurements of diffuse stellar halo light around edge-on disc galaxies
摘要：
测量星系周围的综合恒星晕光是非常具有挑战性的。这些晕的表面亮度预计比黑暗的天空和星系中心亮度低很多量级。在这里，我表明，在最近的一些文献中，非常扩展的点扩散函数（PSF）的尾巴上的测量晕光的效果被低估，特别是在边缘盘星系的情况下。在哈勃超深空探测到的边缘星系短轴上的晕，很大程度上可以用散射的星系光来解释。类似地，根据滤波器和形状的不确定性扩展PSF假设，沿着缩放和堆叠的斯隆数字巡天（SDSS）边缘星系图像的短轴发现的20%至80%的晕光可以通过散射的星系光来解释。散射光也显着有助于堆叠SDSS图像的异常晕颜色。当在远离短轴的象限中观察时，散射光分数减小。剩余的多余的光是很好地模拟与Sersic轮廓晕的形状参数的基础上，恒星计数晕检测附近的星系。尽管PSF散射光的贡献并不能完全消除对这些边缘星系周围扩展组件的需求，但在没有非常仔细的PSF测量和散射光建模的情况下，从集成光中进行精确的光晕形状和颜色测量将是非常具有挑战性的。
英文摘要：
Measuring the integrated stellar halo light around galaxies is very challenging. The surface brightness of these haloes are expected to be many magnitudes below dark sky and the central brightness of the galaxy. Here I show that in some of the recent literature the effect of very extended Point Spread Function (PSF) tails on the measurements of halo light has been underestimated; especially in the case of edge-on disc galaxies. The detection of a halo along the minor axis of an edge-on galaxy in the Hubble Ultra Deep Field can largely be explained by scattered galaxy light. Similarly, depending on filter and the shape one assumes for the uncertain extended PSF, 20 to 80 per cent of the halo light found along the minor axis of scaled and stacked Sloan Digital Sky Survey (SDSS) edge-on galaxy images can be explained by scattered galaxy light. Scattered light also significantly contributes to the anomalous halo colours of stacked SDSS images. The scattered light fraction decreases when looking in the quadrants away from the minor axis. The remaining excess light is well modelled with a Sersic profile halo with shape parameters based on star count halo detections of nearby galaxies. Even though the contribution from PSF scattered light does not fully remove the need for extended components around these edge-on galaxies, it will be very challenging to make accurate halo light shape and colour measurements from integrated light without very careful PSF measurements and scattered light modelling.
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