Consistent dust and gas models for protoplanetary disks I. Disk shape, dust settling, opacities, and PAHs

By Peter Woitke, M. Min, C. Pinte, W. Thi, I. Kamp, C. Rab, F. Anthonioz, S. Antonellini, C. Baldovin-Saavedra, A. Carmona and 12 more. 2015

220 citations recorded by the source corpus.

We propose a set of standard assumptions for the modelling of Class II and III protoplanetary disks, which includes detailed continuum radiative transfer, thermo-chemical modelling of gas and ice, and line radiative transfer from optical to cm wavelengths. The first paper of this series focuses on the assumptions about the shape of the disk, the dust opacities, dust settling, and polycyclic aromatic hydrocarbons (PAHs). In particular, we propose new standard dust opacities for disk models, we present a simplified treatment of PAHs in radiative equilibrium which is sufficient to reproduce the PAH emission features, and we suggest using a simple yet physically justified treatment of dust settling. We roughly adjust parameters to obtain a model that predicts continuum and line observations that resemble typical multi-wavelength continuum and line observations of Class II T Tauri stars. We systematically study the impact of each model parameter (disk mass, disk extension and shape, dust settling, dust size and opacity, gas/dust ratio, etc.) on all mainstream continuum and line observables, in particular on the SED, mm-slope, continuum visibilities, and emission lines including [OI] 63 μm, high-J CO lines, (sub-)mm CO isotopologue lines, and CO fundamental ro-vibrational lines. We find that evolved dust properties, i.e. large grains, often needed to fit the SED, have important consequences for disk chemistry and heating/cooling balance, leading to stronger near- to far-IR emission lines in general. Strong dust settling and missing disk flaring have similar effects on continuum observations, but opposite effects on far-IR gas emission lines. PAH molecules can efficiently shield the gas from stellar UV radiation because of their strong absorption and negligible scattering opacities in comparison to evolved dust. The observable millimetre-slope of the SED can become significantly more gentle in the case of cold disk midplanes, which we find regularly in our T Tauri models. We propose to use line observations of robust chemical tracers of the gas, such as O, CO, and H2, as additional constraints to determine a number of key properties of the disks, such as disk shape and mass, opacities, and the dust/gas ratio, by simultaneously fitting continuum and line observations.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/7d9cf96d254fb62f4ddeda25d66a04d6fc484162

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Citations in the corpus

Global simulations of protoplanetary disks with net magnetic flux: I. Non-ideal MHD case (2016, methodology): “It is known that protoplanetary disks are surrounded by a warm environment of optically thin and well ionized gas (Aresu et al. 2011; Bitsch et al. 2013; Woitke et al. 2016).”
Shadows and spirals in the protoplanetary disk HD 100453 (2016, methodology): “We use a dust mixture made of 70% silicates and 30% carbon (DIANA, Woitke et al. 2016), and the porosity of the grains is set to 25%.”
Equilibrium chemistry down to 100 K (2017, background): “…occur in diluted gases, in particular due to UV-fields, X-rays or cosmic rays as, for example, in protoplanetary discs (e.g. Semenov & Wiebe 2011; Woitke et al. 2016), in the upper layers of planetary atmospheres (e.g. Moses 2014; Rimmer & Helling 2016), or in case of fast hydrodynamical…”
Molecules with ALMA at Planet-forming Scales (MAPS). I. Program Overview and Highlights (2021, background): “The ionization structures of disks depend on a combination of UV and X-ray disk surface fluxes and their radiative transfer, and on cosmic ray ionization (Glassgold et al. 1997; Cleeves et al. 2014a; Woitke et al. 2016; Drabek-Maunder et al. 2016; Rab et al. 2018).”
Direct mapping of the temperature and velocity gradients in discs Imaging the vertical CO snow line around IM Lupi (2017, methodology): “We have implemented a very simple model of the CO chemistry, which was calibrated from ProDiMo models (Woitke et al. 2016, see e.g. their Fig.”
Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics (2017, methodology): “The thermodynamics of the disk atmosphere is much more complex, and detailed modeling would involve UV- and X-ray radiative transfer calculations coupled with photochemistry (e.g., Haworth et al. 2016; Woitke et al. 2016).”
The Disk Substructures at High Angular Resolution Project (DSHARP). V. Interpreting ALMA Maps of Protoplanetary Disks in Terms of a Dust Model (2018, background): “Exploring all these possible influences is, however, beyond the scope of this paper, and we instead refer to dedicated studies of this subject (for example, Draine 2006; Kataoka et al. 2014, 2015; Woitke et al. 2016; Min et al. 2016; Tazaki et al. 2016; Tazaki & Tanaka 2018).”
The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. II. A Statistical Characterization of Class 0 and Class I Protostellar Disks (2020, methodology): “The dust opacities in our model were parameterized by the maximum grain size (see Table 11) following the method outlined by Woitke et al. (2016).”