We used the spectro-photometric information of ~219 million stars from Gaia's Data Release 3 (DR3) to calculate synthetic, narrowband, metallicity-sensitive CaHK magnitudes that mimic the observations of the Pristine survey, a survey of photometric metallicities of Milky Way stars that has been mapping more than 6500 deg^2^of the northern sky with the Canada-France-Hawaii Telescope since 2015. These synthetic magnitudes were used for an absolute recalibration of the deeper Pristine photometry and, combined with broadband Gaia information, synthetic and Pristine CaHK magnitudes were used to estimate photometric metallicities over the whole sky. The resulting metallicity catalogue is accurate down to [Fe/H]~-3.5 and is particularly suited for the exploration of the metalpoor Milky Way ([Fe/H]16). Combined, both photometric metallicity catalogues include more than two million metal-poor star candidates ([Fe/H]phot<-1.0) as well as more than 200000 and ~8000 very and extremely metal-poor candidates ([Fe/H]phot<-2.0 and <-3.0, respectively). Finally, we show that these metallicity catalogues can be used efficiently, among other applications, for Galactic archaeology, to hunt for the most metal-poor stars, and to study how the structure of the Milky Way varies with metallicity, from the flat distribution of disk stars to the spheroid-shaped metal-poor halo.
Cone search capability for table J/A+A/692/A115/pristine_ca (Photometry catalogue that includes both the synthetic CaHKsyn and the Pristine CaHK photometric information (table 1) (219194028 sources))
Cone search capability for table J/A+A/692/A115/pristine_gaia (Pristine-Gaia synthetic metallicity catalogue (table 2) (52297046 sources))
Cone search capability for table J/A+A/692/A115/pristine_dr1 (Pristine DR1 metallicity catalogue (table 3) (6380652 sources))