Photometry, Centroid and Point-spread Function Measurements in the LSST Camera Focal Plane Using Artificial Stars

IF 3.3 3区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Publications of the Astronomical Society of the Pacific Pub Date : 2023-12-01 DOI:10.1088/1538-3873/ad0a73

Johnny H. Esteves, Yousuke Utsumi, Adam Snyder, Theo Schutt, Alex Broughton, Bahrudin Trbalic, Sidney Mau, Andrew Rasmussen, Andrés A. Plazas Malagón, Andrew Bradshaw, Stuart Marshall, Seth Digel, James Chiang, Eli Rykoff, Chris Waters, Marcelle Soares-Santos, Aaron Roodman

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引用次数: 0

Abstract

The Vera C. Rubin Observatory’s LSST Camera (LSSTCam) pixel response has been characterized using laboratory measurements with a grid of artificial stars. We quantify the contributions to photometry, centroid, point-spread function size, and shape measurement errors due to small anomalies in the LSSTCam CCDs. The main sources of those anomalies are quantum efficiency variations and pixel area variations induced by the amplifier segmentation boundaries and “tree-rings”—circular variations in silicon doping concentration. This laboratory study using artificial stars projected on the sensors shows overall small effects. The residual effects on point-spread function (PSF) size and shape are below 0.1%, meeting the ten-year LSST survey science requirements. However, the CCD mid-line presents distortions that can have a moderate impact on PSF measurements. This feature can be avoided by masking the affected regions. Effects of tree-rings are observed on centroids and PSFs of the artificial stars and the nature of the effect is confirmed by a study of the flat-field response. Nevertheless, further studies of the full-focal plane with stellar data should more completely probe variations and might reveal new features, e.g., wavelength-dependent effects. The results of this study can be used as a guide for the on-sky operation of LSSTCam.

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利用人造恒星测量 LSST 相机焦平面的光度、中心点和点散布函数

Vera C. Rubin天文台的LSST相机（LSSTCam）的像素响应是通过实验室测量人造恒星网格来确定的。我们量化了 LSSTCam CCD 的微小异常对光度、中心点、点散布函数大小和形状测量误差的影响。这些异常的主要来源是放大器分割边界和 "树环"（硅掺杂浓度的圆形变化）引起的量子效率变化和像素面积变化。这项使用投射到传感器上的人造星进行的实验室研究显示，总体影响较小。对点散射函数（PSF）大小和形状的残余影响低于 0.1%，符合 LSST 十年巡天科学要求。不过，CCD 中线的扭曲会对 PSF 测量产生一定影响。可以通过遮挡受影响区域来避免这一问题。在人造星的中心点和 PSF 上观测到了树环效应，对平场响应的研究证实了这种效应的性质。不过，利用恒星数据对全焦面的进一步研究应该能更全面地探查各种变化，并可能揭示出新的特征，例如与波长有关的效应。本研究的结果可作为 LSSTCam 在天空中运行的指导。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Publications of the Astronomical Society of the Pacific 地学天文-天文与天体物理

CiteScore

6.70

自引率

5.70%

发文量

103

审稿时长

4-8 weeks

期刊介绍： The Publications of the Astronomical Society of the Pacific (PASP), the technical journal of the Astronomical Society of the Pacific (ASP), has been published regularly since 1889, and is an integral part of the ASP''s mission to advance the science of astronomy and disseminate astronomical information. The journal provides an outlet for astronomical results of a scientific nature and serves to keep readers in touch with current astronomical research. It contains refereed research and instrumentation articles, invited and contributed reviews, tutorials, and dissertation summaries.