Efficiency of radial transport of ices in protoplanetary disks probed with infrared observations: the case of CO${}_2$

Abstract

The efficiency of radial transport of icy solid material from outer disk to the inner disk is currently unconstrained. Efficient radial transport of icy dust grains could significantly alter the composition of the gas in the inner disk. Our aim is to model the gaseous CO${}_2$ abundance in the inner disk and use this to probe the efficiency of icy dust transport in a viscous disk. Features in the simulated CO${}_2$ spectra are investigated for their dust flux tracing potential. We have developed a 1D viscous disk model that includes gas and grain motions as well as dust growth, sublimation and freeze-out and a parametrisation of the CO${}_2$ chemistry. The thermo-chemical code DALI was used to model the mid-infrared spectrum of CO${}_2$, as can be observed with JWST-MIRI. CO${}_2$ ice sublimating at the iceline increases the gaseous CO${}_2$ abundance to levels equal to the CO${}_2$ ice abundance of $\sim 10^{-5}$, which is three orders of magnitude more than the gaseous CO${}_2$ abundances of $\sim 10^{-8}$ observed by Spitzer. Grain growth and radial drift further increase the gaseous CO${}_2$ abundance. A CO${}_2$ destruction rate of at least $10^{-11}$ s${}^{-1}$ is needed to reconcile model prediction with observations. This rate is at least two orders of magnitude higher than the fastest known chemical destruction rate. A range of potential physical mechanisms to explain the low observed CO${}_2$ abundances are discussed. Transport processes in disks can have profound effects on the abundances of species in the inner disk. The discrepancy between our model and observations either suggests frequent shocks in the inner 10 AU that destroy CO${}_2$, or that the abundant midplane CO${}_2$ is hidden from our view by an optically thick column of low abundance CO${}_2$ in to the disk surface XDR/PDR. Other molecules, such as CH${}_4$ or NH${}_3$, can give further handles on the rate of mass transport.

Accepted for publication in A&A, 18 pages, 13 figures, abstract abridged

References in corpus (23)

• 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
• The stickiness of micrometer-sized water-ice particles
• The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects II: CO2
• Complex organic molecules in protoplanetary disks
• Chemical enrichment of giant planets and discs due to pebble drift
• Constraining the X-ray and Cosmic Ray Ionization Chemistry of the TW Hya Protoplanetary Disk: Evidence for a Sub-interstellar Cosmic Ray Rate
• Lupus disks with faint CO isotopologues: low gas/dust or large carbon depletion?
• Mass measurements in protoplanetary disks from hydrogen deuteride
• Setting the volatile composition of (exo)planet-building material. Does chemical evolution in disk midplanes matter?
• Challenges in Planet Formation
• Excess C/O and C/H in outer protoplanetary disk gas
• Formation of simple organic molecules in inner T Tauri disks
• Cometary ices in forming protoplanetary disc midplanes
• H-atom bombardment of CO2, HCOOH and CH3CHO containing ices
• HD far infrared emission as a measure of protoplanetary disk mass
• Ro-vibrational excitation of an organic molecule (HCN) in protoplanetary disks
• Variable H${}^{13}$CO${}^{+}$ Emission in the IM Lup Disk: X-ray Driven Time-Dependent Chemistry?
• The chemistry of planet-forming regions is not interstellar
• A critical analysis of shock models for chondrule formation

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• The dry and carbon poor inner disk of TW Hya: evidence for a massive icy dust trap
• CO2-rich protoplanetary discs as a probe of dust radial drift & trapping
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• Planet formation in the PDS 70 system: Constraining the atmospheric chemistry of PDS 70b and c
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• Molecules with ALMA at Planet-forming Scales (MAPS). XV. Tracing protoplanetary disk structure within 20 au