Different dust and gas radial extents in protoplanetary disks: consistent models of grain growth and CO emission

Abstract

ALMA observations of protoplanetary disks confirm earlier indications that there is a clear difference between the dust and gas radial extents. The origin of this difference is still debated, with both radial drift of the dust and optical depth effects suggested in the literature. In this work, the feedback of realistic dust particle distributions onto the gas chemistry and molecular emissivity is investigated, with a particular focus on CO isotopologues. The radial dust grain size distribution is determined using dust evolution models that include growth, fragmentation and radial drift. A new version of the code DALI is used to take into account how dust surface area and density influence the disk thermal structure, molecular abundances and excitation. The difference of dust and gas radial sizes is largely due to differences in the optical depth of CO lines and millimeter continuum, without the need to invoke radial drift. The effect of radial drift is primarily visible in the sharp outer edge of the continuum intensity profile. The gas outer radius probed by ${}^{12}$CO emission can easily differ by a factor of $\sim 2$ between the models for a turbulent $\alpha$ ranging between typical values. Grain growth and settling concur in thermally decoupling the gas and dust components, due to the low collision rate with large grains. As a result, the gas can be much colder than the dust at intermediate heights, reducing the CO excitation and emission, especially for low turbulence values. Also, due to disk mid-plane shadowing, a second CO thermal desorption (rather than photodesorption) front can occur in the warmer outer mid-plane disk. The models are compared to ALMA observations of HD 163296 as a test case. In order to reproduce the observed CO snowline of the system, a binding energy for CO typical of ice mixtures needs to be used rather than the lower pure CO value.

26 pages, 25 figures, accepted for publication in A&A, abstract shortened to fit arXiv requirements

References in corpus (39)

• Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
• Protoplanetary Disk Structures in Ophiuchus
• Gas- and dust evolution in protoplanetary disks
• Particle Stirring in Turbulent Gas Disks: Including Orbital Oscillations
• Closed-form expressions for particle relative velocities induced by turbulence
• A Submillimeter View of Circumstellar Dust Disks in $\rho$ Ophiuchus
• The stickiness of micrometer-sized water-ice particles
• Dust size distributions in coagulation/fragmentation equilibrium: Numerical solutions and analytical fits
• The chemical history of molecules in circumstellar disks. I. Ices
• Protoplanetary disk masses from CO isotopologues line emission
• Lupus disks with faint CO isotopologues: low gas/dust or large carbon depletion?
• Dust settling in local simulations of turbulent protoplanetary disks
• Hydrocarbon emission rings in protoplanetary disks induced by dust evolution
• The Coupled Physical Structure of Gas and Dust in the IM Lup Protoplanetary Disk
• Mass measurements in protoplanetary disks from hydrogen deuteride
• Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA
• Challenges in Planet Formation
• Gas and Dust Emission at the Outer Edge of Protoplanetary Disks
• The Impact of Dust Evolution and Photoevaporation on Disk Dispersal
• Millimeter imaging of HD 163296: probing the disk structure and kinematics
• Global MHD simulations of stratified and turbulent protoplanetary discs. II. Dust settling
• Thermal desorption of circumstellar and cometary ice analogs
• Robustness of N2H+ as tracer of the CO snowline
• Investigating grain growth in disks around southern T Tauri stars at millimetre wavelengths
• A tidal encounter caught in the act: modelling a star-disc fly-by in the young RW Aurigae system
• Tracing water vapor and ice during dust growth
• Protoplanetary disc evolution affected by star-disc interactions in young stellar clusters
• Chemistry and line emission from evolving Herbig Ae disks
• Chemical Modelling of Young Stellar Objects, I. Method and Benchmarks
• Strong effect of the cluster environment on the size of protoplanetary discs?
• The Role of Ice Compositions for Snowlines and the C/N/O Ratios in Active Disks
• Ro-vibrational excitation of an organic molecule (HCN) in protoplanetary disks
• Stacking Spectra in Protoplanetary Disks: Detecting Intensity Profiles from Hidden Molecular Lines in HD 163296
• Jets, accretion, coronae and all that: The enigmatic X-rays from the Herbig star HD 163296
• A Surface Density Perturbation in the TW Hydrae Disk at 95 au Traced by Molecular Emission
• Grand challenges in protoplanetary disc modelling
• Measuring protoplanetary disk gas surface density profiles with ALMA
• Photochemical-dynamical models of externally FUV irradiated protoplanetary discs
• Dust crystallinity in protoplanetary disks: the effect of diffusion/viscosity ratio

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