DFG Research Unit: FOR 2634/1
... are planet forming disks with inner holes. The origins of those structures are still unknown. They might be caused directly by planets or be formed by dynamical processes linked to the formation of planets. As such, they represent witnesses and probes to the formation of planets.
Credit: ESO/L. Calçada
Recent surveys have shown an overwhelming diversity of extrasolar planetary
systems, prompting the question of how did they form, and whether some may end up looking
like our own and being able to sustain
life. Hints to answer such fundamental questions may be hidden in the many trends that
are slowly emerging from the data. An example are the deserts and peaks in the
distribution of giant exoplanets, with clear implications for habitability
of systems, given the role played by giants on the delivery of volatiles to terrestrial
planets (e.g., Quintana & Lissauer 2014). The environment in which planets form plays a
major role in understanding both the variety of exoplanets
and the emerging trends. Planets are born out of the dust and gas left over whenever a
new star forms: the protoplanetary disk. The initial conditions for planet formation are
thus determined by the protoplanetary disks, which evolve
and disperse as they give birth to planets.
ALMA (ESO/NAOJ/NRAO)/Nienke van der Marel
TDs are only now really becoming spatially resolvable thanks to facilities like
ALMA and VLT - SPHERE, making their study a timely and urgent task. Only understanding
the disk evolution and the planet-disk
interactions allow the large body of existing and planned observations to be exploited to
answer more complex questions like the formation of planetary systems capable to host
life. This requires a focussed effort from several communities
to devise a multi-pronged strategy to approach to tackle the problem. Specifically,
multiwavelength observations of disks at different stages of evolution together with
exoplanet and disk statistics should be used to constrain a concerted
theoretical modelling effort including the hydrodynamics of the dust and gas component of
disks, with and without planets, joint to chemical and radiative transfer calculations,
particularly of the surface layers and winds of disks
in (or just before) the transition phase. This is the motivation for the Research Unit.
Project A1 focusses on collecting and analysing existing ALMA data and complementing those with additional ALMA, VLA and high-contrast infrared imaging observations. The aim is to characterize the content and properties of solids and gas in TDs and to compare with the demographical properties of evolving disk populations. Evidence for dust and gas evolution, including grain growth, and planet-disk interactions will be characterised in order to provide direct observational tests of planet formation and dispersal theories, necessary to interpret the observational appearance of Type 1 and 2 TDs.
The focus of project A2 is on the central star properties and their relation to the accretion properties of the disk, which may be modulated by the disk dispersal mechanisms that lead to the formation of TDs.
Credit: NASA/JPL-Caltech
Building the most comprehensive radiation-hydrodynamical calculations of irradiated disks, coupled to photoionisation, chemistry and radiative transfer calculations for a large parameter space, covering stars of different masses and X-ray properties.
This will constitute the backbone for the work carried out in several projects, which together aim at performing quantitative spectroscopy of disk winds.
Comparison with existing and upcoming observations will allow us to constrain the mass loss rates and the launching regions of the wind and thus pin down the underlying driving disk dispersal mechanism. The models developed in this project will also the able to tackle several important outstanding questions about the formation and evolution of Transition Discs.
| Parameter | Value | Units | ||
|---|---|---|---|---|
| Overview of the code details used to perform the numerical analysis of Transition Discs presented in this Project Area. | ||||
| Code | PLUTO | Mignone et al., 2007 | ||
| Coordinate system | 2D spherical | $r - \theta$ | ||
| Physical range | $0.33$-$1000$ | au | ||
| $0.005$-$\pi/2$ | rad | |||
| Numerical resolution | $412$ | log spaced (l+) | ||
| $160$ | log spaced (l-) | |||
| $\log_{10}{L_\mathrm{X}}$ | $28.3, 29.3, 29.8, 30.3, 31.3, 31.8$ | erg/s | ||
| Inner hole radii | $0,4.6,14.1,21.2,30.3$ | au | ||
In project B1 we will develop the most comprehensive radiation-hydrodynamics models of photoevaporative disk winds to date. The physics beyond the X-ray heated layer will be accounted for for the first time. This will be achieved by coupling the (radiation-)hydrodynamics code PLUTO to an efficient chemical solver for a reduced network, developed in project B2.
Project B2 aims at producing a detailed astrochemical model of the disk atmosphere and its wind. By means of radiative transfer calculations a synthetic spectrum will be obtained to be compared with state-ofthe- art observation of spectrally resolved emission from disks, particularly those with known cavities (TDs). The intensity and profiles of emission lines tracing the base of the wind will allow us to put constraints on the wind-launching mechanism, responsible for the dispersal of the disks.
The dynamics and evolution of dust grains in disks is the main subjects of area C.
In project C1 we will study the growth and trapping of dust grains at hotspots in TDs that may lead to breaking through the meter-size barrier of radial drift, thus allowing the formation of planetesimals. We will use hydrodynamical modelling and dust coagulation models as well as 3D radiative transfer tools. This project will feedback and take inputs from the photoevaporation modelling performed in project B1 and it will eventually produce the underlying dust distributions for project C2.
Project C2 aims at determining the dust content of photoevaporative winds. The latter will make use of state-of-the art models of photoevaporating primordial and TDs from project B1 as well as inputs for the dust distributions from project C1, in order to constrain dust entrainment in the wind, which is an important input to the chemical models in project B2.
Projects in area D aim at constructing realistic simulations of planet-disk interactions and studying the dynamical processes leading to non-axisymmetric features in order to explain the wealth of new and intriguing observations of transitions disks.
Project D1 aims at significantly pushing forward the state-of-the art of (radiation)-hydrodynamical models of gap-forming giant planets embedded in disks including dust dynamics.
Project D2 aims at explaining the surprising non-axisymmetric structures recently observed with ALMA in a number of transition disks, via detailed hydrodynamical and radiative transfer models.
[Internal] D2 Project Slides (K. Dullemond)