An empirical model of the Gaia DR3 selection function

Astronomy and Astrophysics, vol. 669, pp. A55

Abstract

Interpreting and modelling astronomical catalogues requires an understanding of the catalogues’ completeness or selection function: what properties determine an object’s probability of being including in the catalogue? Here we set out to empirically quantify the completeness of the overall catalogue of Gaia ’s third data release (DR3). This task is not straightforward because Gaia is the all-sky optical survey with the highest angular resolution to date and no consistent ground truth exists to allow direct comparisons. However, well-characterised deeper imaging enables an empirical assessment of Gaia ’s G -band completeness across parts of the sky. On this basis, we devised a simple analytical completeness model of Gaia as a function of the observed G magnitude and position over the sky, which accounts for both the effects of crowding and the complex Gaia scanning law. Our model only depends on a single quantity: the median magnitude M 10 in a patch of the sky of catalogued sources with astrometric_matched_transits ≤10. We note that M 10 reflects elementary completeness decisions in the Gaia pipeline and is computable from the Gaia DR3 catalogue itself and therefore applicable across the whole sky. We calibrated our model using the Dark Energy Camera Plane Survey (DECaPS) and tested its predictions against Hubble Space Telescope observations of globular clusters. We found that our model predicts Gaia ’s completeness values to a few per cent (RMS) across the sky. We make the model available as a part of the gaiaunlimited Python package built and maintained by the GaiaUnlimited project.

Authors 15

1. T. Cantat-Gaudin

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

2. M. Fouesneau

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

3. Hans‐Walter Rix

   Max Planck Institute for Astronomy

   Affiliation as printed

   Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

4. A. G. A. Brown Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

5. A. Castro-Ginard Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

6. Z. Kostrzewa-Rutkowska Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

7. R. Drimmel

   Osservatorio Astrofisico di Torino

   Affiliation as printed

   INAF - Osservatorio Astrofísico di Torino, Strada Osservatorio 20, Pino Torinese 10025 Torino, Italy

8. David W. Hogg

   Max Planck Institute for Astronomy · Flatiron Institute · New York University

   Affiliation as printed

   Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Ave, New York, NY 10010, USA

   Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, NY 10003, USA

   Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

9. Andrew R. Casey

   ASTRO-3D · Monash University

   Affiliation as printed

   Centre of Excellence for Astrophysics in Three Dimensions (ASTRO-3D), Melbourne, Victoria, Australia

   School of Physics & Astronomy, Monash University, Clayton 3800, Victoria, Australia

10. S. Khanna

    Osservatorio Astrofisico di Torino

    Affiliation as printed

    INAF - Osservatorio Astrofísico di Torino, Strada Osservatorio 20, Pino Torinese 10025 Torino, Italy

11. Semyeong Oh

    University of Cambridge

    Affiliation as printed

    Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

12. Adrian M. Price-Whelan

    Flatiron Institute

    Affiliation as printed

    Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Ave, New York, NY 10010, USA

13. Vasily A Belokurov

    University of Cambridge

    Affiliation as printed

    Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

14. Andrew K. Saydjari

    Harvard University · Center for Astrophysics Harvard & Smithsonian

    Affiliation as printed

    Department of Physics, Harvard University, 17 Oxford St., Cambridge, MA 02138, USA

    Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA

15. Gregory Green

    Max Planck Institute for Astronomy

    Affiliation as printed

    Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany