Planet-forming disks surrounding newly born stars consist of gas and dust. As their name suggests, they are the birth sites of planetary systems. Thanks to observations from the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA), the chemical composition of the gas can now be studied in great detail. This thesis uses JWST observations to investigate the chemistry of the inner disks (<10 au), where terrestrial planets form, while ALMA observations are used to study that of the outer disks (>10 au).
The JWST observations reveal chemically-rich inner disks around solar-like stars, with strong emission of H2O, CO, CO2, OH, HCN, and C2H2. In particular, analysis of the H2O emission reveals three reservoirs: a cold, a warm, and a hot reservoir. In two sources, the cold H2O reservoir is found to be enhanced following radial drift of icy pebbles and subsequent sublimation, but not in several other disks where this was expected...
Show morePlanet-forming disks surrounding newly born stars consist of gas and dust. As their name suggests, they are the birth sites of planetary systems. Thanks to observations from the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA), the chemical composition of the gas can now be studied in great detail. This thesis uses JWST observations to investigate the chemistry of the inner disks (<10 au), where terrestrial planets form, while ALMA observations are used to study that of the outer disks (>10 au).
The JWST observations reveal chemically-rich inner disks around solar-like stars, with strong emission of H2O, CO, CO2, OH, HCN, and C2H2. In particular, analysis of the H2O emission reveals three reservoirs: a cold, a warm, and a hot reservoir. In two sources, the cold H2O reservoir is found to be enhanced following radial drift of icy pebbles and subsequent sublimation, but not in several other disks where this was expected based on millimeter dust images. Substructures (such as rings and gaps seen in the dust emission) are thought to impede this drift, but analysis of inner disk reservoirs suggests that some gaps may be leaky.
ALMA observations of the outer disk reveal a wide variety of molecular species, from very simple (like CO, CS, and SO) to more complex species, such as H2CO and CH3OH. Observations of disks with large asymmetric dust structures yield a unique opportunity to study the ongoing chemical processes relating gas and ice. Analysis shows that the molecular emission of the disk around Oph-IRS 48 is dominated by sublimation, but that secondary reservoirs due to gas-phase formation routes are also prevalent. The asymmetric disk of HD 142527 reveals, on the other hand, that late-infalling material from the remnant envelope plays a crucial role in setting the chemical composition and can locally enhance elemental ratios, such as the elemental carbon-to-oxygen (C/O) ratio.
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