John McIntyre Conference Centre, Edinburgh, UK

7th - 11th March 2016

Discussion sessions

Here we list the abstracts of the discussion sessions as provided by the proposers. If you would like to pre-suggest topics for discussion, please enter your topics in the form below, they will then be passed on the relevant session organisers:

Discussion topic submission

(1) Structures of transition disks (P. Pinilla)

Recent powerful facilities like ALMA and VLT/SPHERE with their unprecedented sensitivity and spatial resolution have revealed fascinating structures of transition disks at different wavelengths: (eccentric) rings, vortices, asymmetries, dips, and spiral arms. These detailed observations are revolutionising our knowledge on the dynamic processes in transition disks, as a critical evolutionary stage in the formation of planets. Moreover, these new data is also providing information about different parameters which play an important role in the evolution of protoplanetary disks such as disk mass, temperature, magnetic fields, and viscosity. The main goal of this session is to discuss the origin of the observed structures of transition disks by comparing the results from numerical simulations of gas and dust evolution and radiative transfer in disks with the current multiwavelength observations of these disks.

(2) Radiative transfer with LIME (C. Brinch)

We will start this session with a general introduction to the LIME code: what does it do and how does it compare to other codes. We will then move on to talk about how LIME is becoming a community code and how users can contribute and benefit from other user contributions. LIME has recently moved to GitHub and we would like to demonstrate the usefulness of Git and GitHub for a scientific code project such as LIME. In the second part of the session we will discuss the future of the LIME code. We will touch upon topics such as parallelization, new algorithms, error estimation, performance, a new python interface, molecular databases, and very importantly, a new set of benchmark problems.

(3) The role of self-gravitating discs: theory meets observations (F. Meru)

We propose to hold a discussion session on the role of self­gravitating discs. It is clear that these play an important role in the early stages disc evolution as well as planet and brown dwarf formation, determining the initial conditions for late­stage protoplanetary discs and planet formation. This session will involve a critical two­pronged approach of considering observations and theory to determine the importance of processes such as the following in young self­gravitating discs:

To understand these processes in detail it is vital that the theory is used to inform the observations and vice versa. This session will identify where our present theoretical understanding falls short, as well as how the current and future observations can be used to test the theories associated with self­gravitating discs.

We propose a mixture of talks and open discussion. The talks will set the current state of the field including the outstanding issues, followed by thought­provoking questions that will start discussions. This may involve a mixture of large group discussions as well as small breakout sessions.

(4) Observing protoplanetary discs - bringing together the possibilities of current and near-future instrumentation (A. Sicilia-Aguilar)

The recent progress in instrumentation and telescope development has brought us many different ways to observe protoplanetary disks. In addition to new interferometric facilities, space missions, adaptive optics, aperture masking techniques, and integral field spectroscopy, "classical" observations have also suffer a strong evolution thanks to new­generation spectrographs, improved single­dish instrumentation, multi­object capabilities, and time­resolved photometry. The new facilities have thus changed the way we can observe protoplanetary disks ­ and the way we can tackle the existing open problems within disk evolution and dispersal.

The aim of this session will be to put together our knowledge of different and complementary observing techniques towards a collective effort to understand how disks disperse and the connection between different disks and their future planetary systems. The processes involved in disk dispersal are multiple and often lead to degenerate observational signatures. While different observing communities often work independently of each other, the power of combined multi­wavelength, multi­technique observations is a key to substantially improve our understanding of disks, going beyond what a single instrument can show us.

Rosetta stone

The session will be organized as a leaded open discussion with very brief presentations/notes from selected speakers from among the participants. Given that we aim to discuss as many as possible observing techniques and how they can be combined/improved to obtain a more complete picture of disk evolution, the idea is to let as many people as possible talk about their observing techniques to track the properties and evolution of protoplanetary disks, clarifying strengths, weaknesses, missing links, and the way they could be complemented with other observations/observational techniques. This will help to develop collaborations including experts in different kinds of observations. A combined effort is particularly important in case of time­limited space telescope missions, including those that will be available in the near­future.

The theme list for presentations includes so far: High-resolution and velocity-resolved IR spectroscopy, near-IR interferometry, submm and radio interferometry, grain growth, high-contrast polarimetric imaging and SPHERE.

Confirmed participants: Fabien Antonioz, Andrea Banzatti, Andres Carmona, Kevin Flaherty, Antonio Garufi, Jane Greaves, Olja Panic, Tomas Stolker.

(5) The next step: merging hydrodynamic, radiative transfer and chemical models of circumstellar discs (J. D. Ilee)

Traditionally, disc models have been divided in to two communities - ­ those concerned with hydrodynamics (sometimes with the inclusion of magnetic fields and radiation transfer), and those concerned with static radiation­-thermo­-chemical models. While there has been much progress in both fields, there are important areas in which discussion 'across the boundary' is required.

We propose an informal session to discover where progress can be made via collaboration between these communities. For example, how can information on the heating and cooling obtained from thermo­chemical disc models be incorporated in to hydrodynamic models? What are the important dynamical processes that will affect, e.g., the chemistry of static simulations? Conversely, can chemistry also affect the dynamics? Is direct computation of the chemistry the only viable approach, or are there simplified implementations that can be developed?

We will begin the session with three short introductory talks, setting the scene for both communities and discussing current progress and limitations:

We will then identify open questions, and allow for discussion either as a whole, or in smaller groups.

(6) Dynamics of dust: directions for modellers (D. Price)

The physics of gas and dust is deceptively simple yet wildly complex. Few analytic solutions exist that can be used to benchmark numerical codes and there are not yet any standardised comparisons between gas/dust codes on common test problems, let alone on problems relevant to planet formation.

In addition to simple dynamics, there are a huge number of possible approaches to dust physics including prescriptions for grain growth, fragmentation and chemistry of grains, and how to couple radiation codes to hydro codes.

The discussion would first attempt to agree on a few standard test problems, with the eventual aim of kicking off a comparison project on some agreed­upon problems of interest. Second would be to discuss fruitful directions for dust modellers, in particular regarding grain growth models.