The Pristine survey

XXIII. Data Release 1 and an all-sky metallicity catalogue based on Gaia DR3 BP/RP spectro-photometry

¹ Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, 67000 Strasbourg, France
² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
³ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
⁴ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁵ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
⁶ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Piero Gobetti 93/3, 40129 Bologna, Italy
⁷ Department of Physics and Astronomy, University of Victoria, PO Box 3055, STN CSC, Victoria, BC V8W 3P6, Canada
⁸ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
⁹ Universidad de La Laguna, Dept. Astrofísica, 38206 La Laguna, Tenerife, Spain
¹⁰ GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92195 Meudon, France
¹¹ NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
¹² Department of Astronomy & Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada
¹³ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
¹⁴ Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
¹⁵ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
¹⁶ Núcleo de Astronomía, Facultad de Ingeniería y Ciencias Universidad Diego Portales, Ejército 441, Santiago, Chile
¹⁷ Department of Astronomy, Stockholm University, AlbaNova University Centre, 106 91 Stockholm, Sweden

^★ Corresponding authors; nicolas.martin@astro.unistra.fr; estarkenburg@astro.rug.nl. Both authors contributed equally.

Received: 2 August 2023
Accepted: 27 August 2024

Abstract

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 deg² 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] < −1.0). We make available here the catalogue of synthetic CaHK_syn magnitudes for all stars with BP/RP information in Gaia DR3, as well as an associated catalogue of more than ∼30 million photometric metallicities for high signal-to-noise FGK stars. This paper further provides the first public data release of the Pristine catalogue in the form of higher quality recalibrated Pristine CaHK magnitudes and photometric metallicities for all stars in common with the BP/RP spectro-photometric information in Gaia DR3. We demonstrate that, when available, the much deeper Pristine data greatly enhance the quality of the derived metallicities, in particular at the faint end of the catalogue (G_BP ≳ 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 200 000 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.