Gaia Data Release 3 Processing and validation of BP/RP low-resolution spectral data
Gaia Data Release 3 Processing and validation of BP/RP low-resolution spectral data
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Gaia Data Release 3 BP/RP 低分辨率光谱数据的处理和验证
DOI：
10.1051/0004-6361/202243680
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发表时间：
2023
影响因子：
6.5
通讯作者：
De Angeli F
中科院分区：
文献类型：
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作者：
De Angeli F
ContextBlue (BP) 和 Red (RP) 光度计低分辨率光谱数据是 GaiaData Release 3 (GaiaDR3) 中令人兴奋的新产品之一。这些数据还被用来导出Gaia早期数据版本3中的天体测量和综合光度测量以及GaiaDR3中的天体物理参数和太阳系物体反射光谱。在本文中，我们概述了处理技术，该技术允许将每个源的多个凌星原始卫星数据转换为校准到内部参考系统的组合光谱，从而产生低分辨率BP和RP平均光谱。我们描述了如何克服由于机载仪器的复杂性和各种观察策略而带来的挑战。此外，我们还展示了对结果进行科学验证的亮点。这项工作涵盖了 BP/RP 光谱到自洽平均仪器的内部校准，而 BP/RP 光谱到物理通量和波长的绝对参考系统的校准由随附的 GaiaDR3 论文之一介绍。方法我们通过一系列校准步骤，将大约 650 亿个单独的传输光谱校准到相同的平均 BP/RP 仪器上，包括背景扣除、CCD 几何结构的校准、CCD 效率校准的迭代程序以及线扩散函数以及焦平面上和时间上的色散。然后，将每个源的校准传输光谱组合起来，扩展到连续基函数。我们讨论了这些基函数的配置。结果覆盖了光学到近红外波长范围 [330, 1050] nm 的大约 2.2 亿个物体的时间平均光谱已发布。其中大多数比 G= 17.65 更亮，但一些 BP/RP 光谱已发布，其光源的亮度低于 G= 21.43。它们的信噪比 (S/N) 在所覆盖的波长范围内以及所观察物体的幅度和颜色变化很大，G= 15 左右的源在某些波长范围内的 S/N 高于 100。对于星等为 9 <G< 12 的光源，可以获得高质量的 BP/RP 光谱，在 RP 波长范围的中心部分，S/N 达到 1000。科学验证表明内部校准总体上是成功的。然而，有一些证据表明亮端 G< 11 处的校准不完美，其中校准的 BP/RP 光谱可能会表现出超出其估计通量不确定性的系统通量变化。我们还报告说，由于长程噪声相关性，BP/RP 光谱在伪波长采样时会出现摆动。结论 GaiaDR3 数据产品分别是 BP 和 RP 的展开系数和相应的协方差矩阵。鼓励用户使用这种格式的数据，完整的协方差信息表明系数之间的相关性通常非常低。还提供了有关如何访问和使用存档中的 BP/RP 光谱数据的文档和说明。
ContextBlue (BP) and Red (RP) Photometer low-resolution spectral data are one of the exciting new products inGaiaData Release 3 (GaiaDR3). These data have also been used to derive astrometry and integrated photometry inGaiaEarly Data Release 3 and astrophysical parameters and Solar System object reflectance spectra inGaiaDR3.AimsIn this paper, we give an overview of the processing techniques that allow raw satellite data of multiple transits per source to be converted into combined spectra calibrated to an internal reference system, resulting in low-resolution BP and RP mean spectra. We describe how we overcome challenges due to the complexity of the on-board instruments and to the various observation strategies. Furthermore, we show highlights from our scientific validation of the results. This work covers the internal calibration of BP/RP spectra to a self-consistent mean instrument, while the calibration of the BP/RP spectra to the absolute reference system of physical flux and wavelength is covered by one of the accompanyingGaiaDR3 papers.MethodsWe calibrate about 65 billion individual transit spectra onto the same mean BP/RP instrument through a series of calibration steps, including background subtraction, calibration of the CCD geometry, and an iterative procedure for the calibration of CCD efficiency as well as variations of the line-spread function and dispersion across the focal plane and in time. The calibrated transit spectra are then combined for each source in terms of an expansion into continuous basis functions. We discuss the configuration of these basis functions.ResultsTime-averaged mean spectra covering the optical to near-infrared wavelength range [330, 1050] nm are published for approximately 220 million objects. Most of these are brighter thanG= 17.65 but some BP/RP spectra are published for sources down toG= 21.43. Their signal-to-noise ratio (S/N) varies significantly over the wavelength range covered, and with magnitude and colour of the observed objects, with sources aroundG= 15 having a S/N above 100 in some wavelength ranges. The top-quality BP/RP spectra are achieved for sources with magnitudes 9 <G< 12, with S/N reaching 1000 in the central part of the RP wavelength range. Scientific validation suggests that the internal calibration was generally successful. However, there is some evidence for imperfect calibrations at the bright endG< 11, where calibrated BP/RP spectra can exhibit systematic flux variations that exceed their estimated flux uncertainties. We also report that, due to long-range noise correlations, BP/RP spectra can exhibit wiggles when sampled in pseudo-wavelength.ConclusionsTheGaiaDR3 data products are the expansion coefficients and corresponding covariance matrices for BP and RP separately. Users are encouraged to work with the data in this format, with full covariance information showing that correlations between coefficients are typically very low. Documentation and instructions on how to access and use BP/RP spectral data from the archive are also provided.