Prospects from TESS and Gaia to Constrain the Flatness of Planetary Systems

The mutual inclination between planets orbiting the same star provides key information to understand the formation and evolution of multiplanet systems. In this work, we investigate the potential of Gaia astrometry in detecting and characterizing cold Jupiters in orbits exterior to the currently known Transiting Exoplanet Survey Satellite (TESS) planet candidates. According to our simulations, out of the ∼3350 systems expected to have cold Jupiter companions, Gaia, by its nominal 5 yr mission, should be able to detect ∼200 cold Jupiters and measure the orbital inclinations with a precision of ${\sigma }_{\cos i}\lt 0.2$ in ∼120 of them. These numbers are estimated under the assumption that the orbital orientations of the CJs follow an isotropic distribution, but these only vary slightly for less broad distributions. We also discuss the prospects from radial velocity follow-ups to better constrain the derived properties and provide a package to do quick forecasts using our Fisher matrix analysis. Overall, our simulations show that Gaia astrometry of cold Jupiters orbiting stars with TESS planets can distinguish dynamically cold (mean mutual inclination ≲5°) from dynamically hot systems (mean mutual inclination ≳20°), placing a new set of constraints on their formation and evolution.