Gaia DR3 XPmergeXPsampling - Gaia
Gaia DR3 XP-merge / XP-sampling tables
The BP/RP spectra included in the Gaia Data Release 3 (Gaia DR3) are described as a linear combination of continuous basis functions. Each spectrum is fully defined by the array of coefficients to be applied to the bases, the array of coefficients uncertainties and a correlation matrix. The same set of coefficients can be applied to different sets of bases to obtain spectra in the internal reference system (see Gaia DR3 CU5 level paper: Gaia Data Release 3: Processing and validation of BP/RP low-resolution spectral data) or in the absolute flux and wavelength system (see Gaia DR3 CU5 level paper: "Gaia Data Release 3: External calibration of BP/RP low-resolution spectroscopic data").
While the usage of this continuous representation is recommended to make optimal use of the available information and to ensure a full treatment of covariances, there will be use cases that might benefit from a more traditional format of the spectra. The files XpSampling_v375wiv142r.csv and XpMerge_v375wiv142r.csv allow generating spectra sampled on a predefined wavelength grid in the absolute flux reference system starting from the BP/RP mean spectra as provided by the Gaia DR3 archive via Datalink. Sampling on a user-defined wavelength grid is possible using the GaiaXPy Python library. A README file is provided together with the two CSV files to describe their content in detail.
The sampled spectra can be computed by calculating the product of the matrix M stored in XpSampling_v375wiv142r.csv by the vector of the mean spectrum coefficients for each photometer. The resulting vectors (one for BP and one for RP) can be combined by summing their individual element-by-element products with the corresponding merge array from file XpMerge_v375wiv142r.csv. More details about this procedure are available in the GaiaXPy documentation.
These files have been prepared by Coordination Unit 5 of the Gaia Data Processing and Analysis Consortium. If you use this data please cite "Gaia Data Release 3: External calibration of BP/RP low-resolution spectroscopic data" by Montegriffo, et al.
Credits: ESA/Gaia/DPAC and the CU5/DPCI/PhotPipe team.
Published: 13 June 2022