University of Groningen
The future of protoplanetary disk models
Greenwood, Aaron James
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Publication date: 2018
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Greenwood, A. J. (2018). The future of protoplanetary disk models: Brown dwarfs, mid-infrared molecular spectra, and dust evolution. Rijksuniversiteit Groningen.
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Stellingen
behorende bij het proefschrijft
The future of protoplanetary disk models
Brown dwarfs, mid-infrared molecular spectra, and dust evolution
1. Observed systems such as TRAPPIST-1 prove that planets can exist around stars close to the sub-stellar mass limit, and that small planets are likely more common around M-type stars than earlier types. It stands to reason that, given a disk mass of several MJup, brown dwarf disks can form small planets (Chapter 2).
2. Brown dwarf disks are similar to a scaled-down T Tauri disk. With 100 minutes of integration, ALMA will be able to detect and perhaps spatially resolve the sub-mm lines of species such as HCO+, HCN,13CO, and C18O (Chapter 2). 3. To make full use of the spectra from upcoming observatories such as JWST and
E-ELT, we need better to understand our chemical networks and why it is difficult to reproduce observed HCN and C2H2fluxes with 2D models (Chapter 3).
4. Efficient line cooling causes Tgas to drop below Tdust around the AV = 1 line. These gas temperature gradients affect the line emission. For modelling mid-infrared lines it is inaccurate to assume that Tgas=Tdust (Chapter 3).
5. The Tgas, radii, and heights from which species such as CO2and H2O emit are very different. 2D disk models are necessary to accurately model mid-infrared spectral lines and to derive column densities from observations (Chapter 3). 6. The gas-to-dust ratio and dust size distribution can greatly influence mid-infrared
line fluxes. Combining dust evolution with self-consistent settling can reproduce line fluxes as high as have been observed with Spitzer, without ad hoc assumptions such as increasing the gas-to-dust ratio of the entire disk (Chapter 4).
7. All data and relevant code should be accessible alongside published papers. We are obliged not to abuse this, and to consult authors when using their data or code.
8. Funding committees and TACs have the difficult task of distributing resources for which demand far outstrips supply. However, we must be careful not to allow the momentum of research groups with a long-established track record to unilaterally define the direction of research.
9. Climate change is the one of the greatest challenges we have faced. We cannot overcome it while remaining politically divided and blinded by wilful ignorance. 10. Take time to relax, tidy up loose ends, and do the things that make you happy. It
is unsustainable for both professional and personal lives to be chaotic.
Aaron Greenwood Oktober 2018, Groningen
