Chemical Diversity in Protoplanetary Disks and Its Impact on the Formation History of Giant Planets

Giant planets can interact with multiple and chemically diverse environments in protoplanetary discs while they form and migrate to their final orbits. The way this interaction affects the accretion of gas and solids shapes the chemical composition of the planets and of their atmospheres. Here we investigate the effects of different chemical structures of the host protoplanetary disc on the planetary composition. We consider both scenarios of molecular (inheritance from the pre-stellar cloud) and atomic (complete chemical reset) initial abundances in the disc. We focus on four elemental tracers of different volatility: C, O, N, and S. We explore the entire extension of possible formation regions suggested by observations by coupling the disc chemical scenarios with N-body simulations of forming and migrating giant planets. The planet formation process produces giant planets with chemical compositions significantly deviating from that of the host disc. We find that the C/N, N/O, and S/N ratios follow monotonic trends with the extent of migration. The C/O ratio shows a more complex behaviour, dependent on the planet accretion history and on the chemical structure of the formation environment. The comparison between S/N* and C/N* (where * indicates normalisation to the stellar value), constrains the relative contribution of gas and solids to the total metallicity. Giant planets whose metallicity is dominated by the contribution of the gas are characterised by N/O* > C/O* > C/N* and allow for constraining the disc chemical scenario. When the planetary metallicity is instead dominated by the contribution of the solids we find that C/N* > C/O* > N/O*.Comment: 27 pages, 10 figures, 1 table. Published in The Astrophysical Journa

Chemical diversity in protoplanetary discs and its impact on the formation history of giant planets

Comparative studies of protoplanetary discs, exoplanetary systems, and the Solar System revealed the extreme diversity in the orbital architectures of giant planets. Their detection over a wide range of orbital radii, spanning from 0.01 to 100 au from the host star, suggests that giant planets can interact with multiple and diverse chemical environments in protoplanetary discs while they form and migrate to their final orbits. Specifically, migration allows giant planets to grow by accreting gas and solids characterised by different compositions and relative abundances of refractory and volatile elements. The interplay between accretion and migration shapes the composition of giant planets and of their atmospheres: as such, the composition of planetary atmospheres can be used as a proxy into the formation and migration histories of giant planets. An extensive body of work investigated how the abundance ratio of the elements C and O allows to probe the formation pathways of giant planets, though most studies focused on formation regions closer to the star than suggested by observations. To explore the implications of such wider formation regions, we coupled N-body simulations of forming and migrating giant planets with astrochemical models of protoplanetary discs. In parallel, we extended the set of chemical tracers to include one of the most volatile elements, N, and one of the most refractory ones, S to enhance the set of elemental ratios. In this talk we discuss the implications of different disc astrochemical scenarios for the final composition of giant planets, and show how the enhanced set of elemental ratios can be used to constrain both the extent of migration and the sources of the planetary metallicity in both chemical inheritance and reset scenarios of the host protoplanetary disc...

The formation history of giant planets seen through multiple elemental ratios

Comparative studies of protoplanetary disks, exoplanetary systems, and the Solar System reveal the presence of giant planets over a wide range of orbital radii, spanning from 0.01 to 100 au from the host star. This great diversity of architectures suggests that giant planets can interact with multiple and diverse chemical environments in protoplanetary disks while they form and migrate to their final orbits, accreting gas and solids with different compositions and relative abundances of refractory and volatile elements. The interplay between accretion and migration shapes the composition of giant planets and of their atmospheres: as such, the composition of planetary atmospheres can be used as a proxy into the formation and migration histories of giant planets. We explore the implications of the wider formation regions suggested by observations coupling N-body simulations of forming and migrating giant planets with astrochemical models of protoplanetary discs. In our analysis we expand the set of elemental ratios we trace by including one of the most volatile elements, N, and one of the most refractory ones, S, to complement the information provided by C and O. In this talk we discuss the implications of different disk astrochemical scenarios for the final composition of giant planets, and show how this enhanced set of elemental ratios can be used to constrain both the extent of migration and the sources of the planetary metallicity in both chemical inheritance and reset scenarios of the host protoplanetary disk...