On the Exoplanet Yield of Gaia Astrometry

TL;DR

This study predicts Gaia's astrometric mission will detect thousands of exoplanets, mainly super-Jupiters around GKM stars, with detailed estimates of detection numbers, measurement precision, and false-positive rates, aiding future data analysis.

Contribution

It provides updated, detailed forecasts of Gaia's exoplanet detection yield using refined models and simulations, including mock catalogs for community use.

Findings

Approximately 7,500 planets in DR4 and 120,000 in DR5 predicted

Most detections are super-Jupiters on 2-5 AU orbits around GKM stars

False positives from binaries are significant, especially for planets around M-dwarfs

Abstract

We re-examine the expected yield of Gaia astrometric planet detections using updated models for giant-planet occurrence, the local stellar population, and Gaia's demonstrated astrometric precision. Our analysis combines a semi-analytic model that clarifies key scaling relations with more realistic Monte Carlo simulations. We predict $7{,}500 \pm 2{,}100$ planet discoveries in the 5-year dataset (DR4) and $120{,}000 \pm 22{,}000$ over the full 10-year mission (DR5), with the dominant error arising from uncertainties in giant-planet occurrence. We evaluate the sensitivity of these forecasts to the detection threshold and the desired precision for measurements of planet masses and orbital parameters. Roughly $1{,}900 \pm 540$ planets in DR4 and $38{,}000 \pm 7{,}300$ planets in DR5 should have masses and orbital periods determined to better than $20$%. Most detections will be super-Jupiters ($3$ - $13 M_{\rm J}$) on $2$ - $5$AU orbits around GKM-type stars ($0.4$ - $1.3 M_\odot$) within $500$ pc. Unresolved binary stars will lead to spurious planet detections, but we estimate that genuine planets will outnumber them by a factor of $5$ or more. An exception is planets around M-dwarfs with $a < 1$AU, for which the false-positive rate is expected to be about $50$%. To support community preparation for upcoming data releases, we provide mock catalogs of Gaia exoplanets and planet-impostor binaries.