Internal calibration of Gaia BP/RP low-resolution spectra
Internal calibration of Gaia BP/RP low-resolution spectra
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DOI：
10.1051/0004-6361/202141249
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发表时间：
2021-06
影响因子：
6.5
通讯作者：
J. Carrasco;M. Weiler;C. Jordi;C. Fabricius;F. De Angeli;D. Evans;F. van Leeuwen;M. Riello
中科院分区：
文献类型：
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作者：
J. Carrasco;M. Weiler;C. Jordi;C. Fabricius;F. De Angeli;D. Evans;F. van Leeuwen;M. Riello
上下文。完整的第三次Gaia数据发布将首次提供用蓝色和红色Gaia无缝分光谱仪(分别为BP和RP)获得的校准光谱。盖亚是一项非常复杂的任务，不能被认为是单一的工具，而是同样多个工具。这两条视线的视场很宽，在100多个不同的探测器上，整个大焦面上的观测结果有很大的变化。面对GAIA光谱校准的主要挑战是，在执行任务期间没有LAMP光谱或平坦的视场可用。此外，相对于棱镜色散的线扩展函数的显著大小会产生污染光谱的邻近位置的外来光子。这使得校准变得特殊，不同于标准方法。目标。这项工作详细描述了用于获得GAIA星表内容的分光光度数据的内部校准模型。内部校准的主要目的是将所有历元光谱放在一个共同的通量和像素(伪波长)尺度上，同时考虑到焦面上的变化和随时间的变化，从同一震源的所有观测产生平均光谱。方法：研究方法。为了描述在共同的平均通量和伪波长尺度上的所有观测，我们用基函数构造了内定标平均谱的适当表示，并通过离散卷积描述了未定标历元谱和定标平均谱之间的转换，参数提升卷积核以恢复相关系数。结果。这里提出的GAIA分光光度观测值内部校准模型能够将所有观测值合并到一个平均值仪器中，以便能够比较不同来源和在飞行任务中不同仪器条件下获得的观测值，并根据同一来源的若干观测数据生成平均光谱。我们推导出了一个能够处理问题的自校准性质的校准模型。该模型的输出提供了内部平均光谱，不是作为采样函数(通量和波长)，而是作为基函数的线性组合，尽管采样光谱可以很容易地从它们得到。
Context. The full third Gaia data release will provide, for the first time, the calibrated spectra obtained with the blue and red Gaia slitless spectrophotometers (BP and RP, respectively). Gaia is a very complex mission and cannot be considered as a single instrument, but rather as many instruments. The two lines of sight with wide fields of view introduce strong variations of the observations across the large focal plane with more than one hundred different detectors. The main challenge when facing Gaia spectral calibration is that no lamp spectra or flat fields are available during the mission. Also, the significant size of the line spread function with respect to the dispersion of the prisms produces alien photons contaminating neighbouring positions of the spectra. This makes the calibration special and different from standard approaches. Aims. This work gives a detailed description of the internal calibration model for the spectrophotometric data used to obtain the content of the Gaia catalogue. The main purpose of the internal calibration is to bring all the epoch spectra onto a common flux and pixel (pseudo-wavelength) scale, taking into account variations over the focal plane and with time, producing a mean spectrum from all the observations of the same source. Methods. In order to describe all observations on a common mean flux and pseudo-wavelength scale, we constructed a suitable representation of the internally calibrated mean spectra via basis functions, and we described the transformation between non-calibrated epoch spectra and calibrated mean spectra via a discrete convolution, parametrising the convolution kernel to recover the relevant coefficients. Results. The model proposed here for the internal calibration of the Gaia spectrophotometric observations is able to combine all observations into a mean instrument to allow the comparison of different sources and observations obtained with different instrumental conditions along the mission and the generation of mean spectra from a number of observations of the same source. We derived a calibration model that can handle the self-calibrating nature of the problem. The output of this model provides the internal mean spectra, not as a sampled function (flux and wavelength), but as a linear combination of basis functions, although sampled spectra can easily be derived from them.