Formation and evolution of planetary systems – DiskEvol
Formation and evolution of planetary system
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The main objective of DiskEvol is to bridge the gap between two research fields in the study of protoplanetary disks. The first focuses in the millimeter regime, particularly molecular emission lines, to derive the kinematics and abundances of the gas within the disk. The focus of the second is on the optical and infrared observations, which study in detail the dust component. The individual information from the dust and gas components is almost never used conjointly, hence limiting our ability to precisely understand the structure and evolution processes of disks. To overcome this limitation, it is necessary to model the gas and dust observations as coherently as possible in the framework of a single model. We have developed one of the most powerful radiative transfer codes: MCFOST, which can calculate both continuum and line transfer coherently. Through DiskEvol, we will build a team that will perform a systematic, simultaneous modelling of the dust and gas observations of disks using MCFOST, in particular the observations from the Herschel project GASPS, so as to characterise the physical and chemical conditions within disks, and from this assess, the main evolution processes of disks and from this assess, the main evolution processes of disks. Two parallel and complementary approaches will be followed: 1) a statistical comparison of the observations of the whole GASPS sample with large grids of models and 2) a detailed fitting of a selected sample of sources with high-quality datasets combining line observations, SEDs and resolved continuum maps (scattered light images and/or (sub-)mm visibilities). This work will rely on numerical developments to couple the chemistry and radiative transfer codes available at IPAG : ProDiMo and MCFOST.
The research program is organised in 3 main tasks :
Task 1: Database of observations and models for the GASPS project The goal is to provide complementary data in the millimeter regions for the GASPS source and to make this data quickly available within the consortium. The second objective is to build tools that will allow detailed interpretation of these data sets. We will compute a grid of radiative transfer models with MCFOST (SEDs and line fluxes for the lines observed by GASPS) over a wide range of spectral types and disk parameters. The ultimate objective of this first task is to build a uniform and easy-to- access set of data (observations and models) that will be intensively used for interpretation.
Task 2: Analysis of the GASPS results: a dust and gas inventory of disks We will interpret the observed signatures of both the dust and gas with respect to the aforementioned grid of models. The statistical comparison of the grid of models with the observational data sets will offer us the ability to interpret observational trends in terms of model parameters. We will search for the most direct signatures of disk evolution: inner hole size, gas mass and chemical state, dust growth and settling in order to estimate the timescales for evolution and set constraints on the processes at work.
Task 3: A complete view of the dust structure and gas chemistry in disks To characterise the processes by which disks evolve, the statistical results of task 2 must be completed by model fitting of a selected sample of representative sources, which will serve as references for the global analysis. We will precisely analyse CO molecular maps of this selected sample of disks. This will allow us to constrain the kinematics and dynamics of the gas, to measure the gas scale height and temperature and compare them to the dust ones, as well as analyse water molecule lines to constrain the physical conditions of the molecular gas in the planet forming region of protoplanetary disks.
Progress has been on all aspects of the project and accordingly to
the initial plan. 28 refereed publications have resulted from this work so far.
Task 1 :
- the anciallary data sets from IRAM have been reduced and published (Mathews et al 2012).
- A new collaboration on the analysis and publication of Herschel data on a sample of brown dwarfs (Harvey et al 2011, 2012) has been initiated.
- A new program to detect edge-on disk with HST has been initiated, resulting in 8 discoveries
- The program to collect interferometric data with PIONIER has started as well as its analysis with complementary data, for instance from Herschel DIGIT.
Task 2 :
- New modelling tools have been set up to compare the observational data with models in a very efficient way (parallel genetic and MCMC algorithms which have been tailored to the problem).
- Study of the results of the DENT grid : establishing diagnostics for the gaz in disks.
- Modelling of the SEDs of the Taurus objects (Pinte et al, in prep.) and
Upper Sco.
- The analysis of the statististical results of GASPS has led to several
publications : for Herbig Ae stars (Meeus et al 2012), the detection of water in the disks in Taurus (Riviere et al 2012), the comparison of the emission from disks and jets (Podio et al 2012), the detection of CH+ around HD 100546 (Thi et al 2011).
Task 3 :
- Detailed modelling of the disks surounding TW Hydra, HD163296,
HK Tau, T Cha, HD 100546, HD 181327, HD 172555/
- Developping the tools to study the CO ro-vibrational lines (HD135344 B, Carmona et al 2013).
- Studying the effect of the water chenistry and of the details of radiative transfer on water emission lines (Kamp et al 2013)
- Interfacing the mcfost code with the LIDT code from CEA/Saclay (S. Charnoz) and phantom code (D. Price, G. laibe) to study the evolution of dust grains in disks.
The studies developped in DIskEvol will become more influential with the advent of the ALMA interferometer and JWST space telescopes, that will complement Herschel observations at both longer and shorter wavelengths. ALMA is providing images and velocity maps at high spatial resolution (and not only integrated quantities as in the case of Herschel). It probes the density, temperature and abundance gradients non only in the external parts of disks but also closer to the star, at spatial scales of the order of 10 AU. Er are now at a point where we can predict, using the aforementioned RT / chemistry codes (MCFOST and ProDiMo), the emission maps (continuum and molecular lines), as they will be seen by ALMA, and to determine the spatial dependence of the physico-chemical conditions. JWST’s imaging and spectroscopy capabilities will complement Herschel observations at shorter wavelengths, and in particular will determine more precisely than Spitzer the constituents of the dust grains, it will observed the highly excited hot CO (ro-vibrational bands around 2.3 and 4.6 µm) in the central regions of the disks, and will study organic molecules that are important for life to develop.
In particular, the GASPS sources, for which we will have detailed models, are very likely to be priority targets for ALMA and JWST. We will use the results of the aforementioned tasks to make predictions regarding the observable consequences of gas and dust evolution, and planet formation. These aspects are key drivers for both instruments and our calculations will provide the best estimates, closest to reality, for signatures of evolution in disks.
Howard et al., 2013, ApJ, 776, 21
Mathews, Pinte, Duchene, Williams, and Menard, 2013, A&A, 558, A66
de Gregorio-Monsalvo et al., 2013, A&A, 557, A133
Thi et al., 2013, A&A, 557, A111
Canovas et al., 2013, A&A, 556, A123
Riviere-Marichalar et al., 2013, A&A, 555, A67
Dent et al., 2013, PASP, 125, 477
Olofsson et al., 2013, A&A, 552, A4
Podio et al., 2013, ApJl, 766, L5
Cieza et al., 2013, ApJ, 762, 100
Gonzalez, Pinte, Maddison, Menard, and Fouchet, 2012, A&A, 547, A58
Riviere-Marichalar et al., 2012, A&A, 546, L8
Podio et al., 2012, A&A, 545, A44
Harvey et al., 2012, ApJ, 755, 67
Meeus et al., 2012, A&A, 544, A78
Lebreton et al., 2012, A&A, 539, A17
Riviere-Marichalar et al., 2012, A&A, 538, L3
Tilling et al., 2012, A&A, 538, A20
Mathews et al., 2012, ApJ, 745, 23
Harvey et al., 2012, ApJl, 744, L1
Cieza et al., 2011, ApJl, 741, L25
Melis et al., 2011, ApJl, 739, L7
Kamp et al., 2011, A&A, 532, A85
Patience et al., 2011, A&A, 531, L17
Tatulli et al., 2011, A&A, 531, A1
Thi et al., 2011, A&A, 530, L2
Olofsson et al., 2011, A&A, 528, L6
McCabe et al., 2011, ApJ, 727, 90
Most of our current knowledge of protoplanetary disks originates from studies of the dust component (e.g. spectral energy distributions (SED),
scattered light images, emission maps) despite the fact that dust comprises only 1% of the initial mass of the disk.In contrast, the dominant and
essential gas component of a protoplanetary disk has proven more difficult to observe thus far. Combining the gas and dust information from
protoplanetary disks is particularly important for understanding disk evolution. The Herschel Space Observatory, due to be launched in April of this
year, will open an unexplored wavelength window in the far infrared regime, providing access to high-quality observations of the gas in disks. I have
been invited to join the "GAS in Protoplanetary Systems" (GASPS) Open Time Key Project that will observe both continuum (dust) and line (gas),
namely [CII], [OI] and water, emission for an unbiased sample of 240 young stars, spanning a large range of stellar masses as well as the entire
duration of planet formation.
This DiskEvol program will tackle the complex problem of combining consistently the constraints on the gas phase of a disk, provided by the Herschel
observations, with our existing studies of the dust phase. Interpretation of gas observations is complicated by the large number of physical processes
at play: chemistry, excitation and destruction of molecules, freeze-out onto the dust grains, to name a few. But, this is of particular importance as the
dissipation of abundant gas remnant from star formation limits the timescale for giant planet formation, controls the dynamics of planetary bodies (of
all sizes) during their formation and determines the final architecture of the planetary system.
This proposal will rely on 1) the preparation of a database including observations and models for the GASPS project, resultant from ancillary
data for GASPS in the millimetre regime and the generation of grids of radiative transfer models (SEDs and line fluxes), respectively.
This initial work will allow 2) a detailed analysis of the GASPS program through a statistical comparison of the GASPS observations with
the predictions from the grid of models. This global study, of the large sample of disks observed by GASPS, will be 3) extended and completed
through finer detailed modelling of a selected sample of representative sources for which we will obtain a complete view of the dust structure and gas
chemistry using simultaneous interpretation of continuum observations, resolved emission maps in low-level rotational lines of CO, in addition to
follow-up observations with HIFI, a high-spectral resolution instrument on-board Herschel.
DiskEvol will provide an unprecedented inventory of gas and dust in protoplanetary disks, transforming our understanding of disk evolution by
addressing key questions on the timescales and main mechanisms of dust and gas evolution within disks. In addition, the long-lasting value of
DiskEvol results is of exceptional importance in the era of ALMA and JWST.
Project coordination
Christophe PINTE (CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE RHONE-ALPES SECTEUR ALPES)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partnership
LAOG CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE RHONE-ALPES SECTEUR ALPES
Help of the ANR 150,000 euros
Beginning and duration of the scientific project:
- 36 Months
