詹姆斯·韦伯空间望远镜绝对流量定标 VI：近红外相机成像与日冕仪观测
The James Webb Space Telescope Absolute Flux Calibration. VI. Near-Infrared Camera Imaging and Coronagraphy
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中文总结 AI 辅助
该研究更新了JWST近红外相机的流量定标，首次完成弱透镜及次级日冕仪配置的天基定标，定标因子已纳入JWST pipeline，离散度通常小于2%。
中文摘要 AI 辅助
我们针对JWST近红外相机（NIRCam）的所有成像模式提出了更新后的流量定标方法，该方法可将仪器单位转换为物理表面亮度单位MJy sr⁻¹。本次定标涵盖了19颗流量标准星的观测数据，这些数据跨越3.5年，包含A型矮星、太阳型恒星以及热恒星。我们对全部5种日冕仪配置、全部29种滤光片以及两种弱透镜进行了定标。这是首次针对用于时间序列观测的弱透镜，以及次级日冕仪配置（长波掩模与短波滤光片配对，反之亦然）开展的天基定标工作。我们还评估了子阵列与全帧之间的计数率差异，发现差异最高约为1%，这些差异被纳入定标因子中。研究发现，定标因子的离散度通常小于2%，约一半的滤光片+探测器[+掩模]组合的离散度可达小于1%，且不存在计数率、满阱深度等探测器效应带来的趋势。对大麦哲伦云的少量滤光片图像以及球状星团47 Tuc的图像显示，探测器间的残余偏移通常较小（小于1%），但最高可达4%-5%。研究发现NIRCam探测器稳定性较高，每年可能的计数率下降小于0.4%，该值处于定标不确定度范围内。这些新的定标因子已于2026年3月被纳入JWST pipeline。
英文摘要
We present an updated flux calibration for all imaging modes of the Near-Infrared Camera on JWST that converts instrumental units to physical surface brightness units of MJy sr^-1. This calibration includes observations of 19 flux standard stars spanning 3.5 years, with a mix of A dwarfs, solar analogs, and hot stars. All 5 coronagraphic setups, all 29 filters, and both weak lenses are calibrated. This is the first on-sky calibration for the weak lenses used in Time Series observations and for secondary coronagraphic configurations (long wavelength masks paired with short wavelength filters, and vice versa). We also assess count-rate differences between subarrays and the full frame, finding differences of up to ~1%. These differences are incorporated into the calibration factors. We find that the scatter in the calibration factor is typically <2%, with about half of the filter+detector[+mask] combinations reaching <1% scatter. There are no trends with detector effects such as the count rate and well depth. Images in a handful of filters of the Large Magellanic Cloud and globular cluster 47 Tuc show that residual detector-to-detector offsets are typically small (<1%), but can be as high as 4-5%. The NIRCam detectors are found to be quite stable, with possible count-rate decreases of <0.4% per year, which is within the calibration uncertainties. These new calibration factors were incorporated into the JWST pipeline in 2026 March.
