[论文解读] The Hyper Suprime-Cam extended Point Spread Functions and applications

L. P. Garate-Nuñez, A. S. G. Robotham+3 more|arXiv (Cornell University)|Sep 28, 2023

Adaptive optics and wavefront sensingPhysics and Astronomy被引用 3

一句话总结

本文针对Hyper Suprime-Cam（HSC）公共数据发布3（PDR3）在五个光学波段中提出了扩展点扩散函数（PSF）模型，通过点源的中值叠加方法，将PSF翼部建模至5.6角分。作者证明，去除PSF散射光可改善星系晕内光（IHL）的测量结果，将IHL面亮度的过度估计减少最多达1.7 mag arcsec⁻²，IHL分数减少约30%，在距离中心星系150 kpc处，IHL分数的中位数达到0.13。

ABSTRACT

We present extended point spread function (PSF) models for the Hyper Suprime-Cam Subaru Strategic Program Public Data Release 3 (HSC-SSP PDR3) in all $ extit{g,r,i,Z}$ and $ extit{Y}$-bands. Due to its 8.2m primary mirror and long exposure periods, HSC combines deep images with wide-field coverage. Both properties make HSC one of the most suitable observing facilities for low surface brightness (LSB) studies, which are particularly sensitive to the PSF. By applying a median stacking technique of point-like sources with different brightness, we show how to construct the HSC-SSP PDR3 PSF models to an extent of R $\sim$ 5.6 arcmin. These models are appropriate for the HSC-PDR3 intermediate-state data which do not have applied the final aggressive background subtraction. The intermediate-state data is especially stored for users interested in large extended objects, where our new PSFs provide them with a crucial tool to characterise LSB properties at large angles. We demonstrate that our HSC PSFs behave reasonably in two scenarios. In the first one, we generate 2-D models of a bright star, showing no evidence of residual structures across the five bands. In the second scenario, we recreate the PSF-scattered light on mock images with special consideration of the effect of this additional flux on LSB measurements. We find that, despite the well-behaved nature of the HSC-PDR3 PSFs, there is a non-negligible impact on the faint light present in the mock images. This impact could lead to incorrect LSB measurements if a proper star subtraction is not applied.

研究动机与目标

• 为Hyper Suprime-Cam（HSC）公共数据发布3（PDR3）开发精确的扩展PSF模型，以支持低面亮度（LSB）研究的精确化。
• 解决深空大视场成像中，PSF翼部散射光对低面亮度特征（尤其是星系晕内光IHL）的污染问题。
• 量化PSF散射光对星系群中IHL面亮度和分数测量的影响。
• 为社区提供经过校准的HSC PSF模型及重建脚本，以支持可重复的LSB分析。
• 评估标准面亮度截断（如μ_r^lim = 26.4 mag arcsec⁻²）在分离IHL与星系光方面的可靠性。

提出的方法

• 通过HSC-SSP PDR3中g、r、i、Z和Y波段点源的中值叠加，构建扩展PSF模型。
• 利用明亮和暗淡恒星的组合，将PSF翼部建模至R ~ 5.6角分（对应400020星系群距离的300 kpc）。
• 将PSF模型应用于SXDS场中400020 GAMA星系群的深场HSC图像，以去除散射光。
• 采用先进的源提取方法并结合PSF通量校正，从主星系和星系群光中分离出IHL成分。
• 生成二维PSF模型，并通过重建明亮恒星的光度分布来验证其准确性。
• 对比PSF减除前后IHL面亮度和分数（f_IHL）的测量结果，以量化系统性偏差。

Figure 1: Location of the HSC-Wide (pale blue), Deep (blue), and UltraDeep fields (dark blue) and the GAMA fields (pale red) on the sky in equatorial coordinates. The grey shadow represents the Milky Way (MW) plane and the centre of the MW is indicated by the grey-filled circle. The orange shadow in

实验结果

研究问题

• RQ1 在深空大视场成像中，PSF散射光对星系晕内光（IHL）测量的污染程度如何？
• RQ2 能否通过点源中值叠加方法，为HSC-SSP PDR3构建准确的扩展PSF模型？
• RQ3 在400020 GAMA星系群中，PSF减除对IHL面亮度和IHL分数（f_IHL）测量的影响如何？
• RQ4 标准面亮度截断（如μ_r^lim = 26.4 mag arcsec⁻²）如何影响IHL测量的准确性？
• RQ5 新的HSC PSF模型能否提升大半径处低面亮度特征检测的保真度？

主要发现

• 扩展的HSC PSF模型成功重建了明亮恒星的二维光度分布，验证了其在内区和外区的准确性。
• 若未去除PSF散射光，IHL面亮度在大半径处的测量值最高会被过度估计达1.7 mag arcsec⁻²。
• 当未减除PSF散射光时，IHL分数（f_IHL）被高估约30%，校正后其中位数为0.13。
• 广泛使用的面亮度极限μ_r^lim = 26.4 mag arcsec⁻²会将真实IHL分数低估两倍，且该结果与是否进行PSF减除无关。
• IHL面亮度轮廓可可靠测量至31 mag arcsec⁻²和400020星系群中心星系（BCG）300 kpc的距离。
• HSC-SSP PDR3的PSF模型及重建脚本已公开发布于https://github.com/luciagarate/HSC_PSFs，供社区使用。

Figure 2: Upper: image of a star used to reconstruct the PSF outer part where the ProFound masks are indicated by the semi-transparent gray spots. The normalisation annulus used to stack all the images is delimited by the two black thin circles. Lower: histogram of the flux values of all the pixels