Institut für Astronomie & Astrophysik

Numerical modeling of hydrogen-line emission from accreting gas giants

Yuhiko Aoyama, University of Tokyo, Department of Earth and Planetary Science - 22.10.18


For planetary formation theory, it is important to detect forming planets and to constrain their forming conditions through observations. This is because planets approach an equilibrium state and old planets (like our Jupiter) have lost information about their birth. To observe forming planets, hydrogen lines are a great candidate. Hydrogen lines are emitted by excited hydrogen, thus requiring hot gas, typically above 10'000 K. Such hot gas hardly exists without an accreting shock, i.e., accreting planets. For example, a point source of H alpha was detected in the protoplanetary disk of LkCa 15 and is thought to be caused by an accreting gas giant.

In this study, we numerically simulate the radiated hydrogen line flux from an accreting shock surface. For this, we study the detectability of forming gas giants and discuss which forming conditions are implied by observations. In order to do this, we construct a numerical model just after the shock including 1D hydrodynamics, electron transitions, and radiative transfer. We then demonstrate that the H alpha is strong enough to be detected. By comparing our simulated H alpha intensity and the observed one, we constrain the relation between mass and mass accretion rate.