On the Exoplanet Yield of Gaia Astrometry

Abstract We reexamine 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 semianalytic model that clarifies key scaling relations with more realistic Monte Carlo simulations. We predict 7500 ± 2100 planet discoveries in the 5 yr dataset (Data Release 4 (DR4)) and 120,000 ± 22,000 over the full 10 yr mission (Data Release 5 (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 1900 ± 540 planets in DR4 and 38,000 ± 7300 planets in DR5 should have masses and orbital periods determined to better than 20%. Most detections will be super-Jupiters (3–13 M J ) on 2–5 au orbits around GKM-type stars (0.4–1.3 M ⊙ ) 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. 1 1 https://github.com/CalebLammers/GaiaForecasts