Protoplanetary Disk Structure With Grain Evolution: The Andes Model

Akimkin, V. V.; Zhukovska, Svitlana; Wiebe, D. S.; Semenov, D.; Pavlyuchenkov, Ya. N.; Vasyunin, A. I.; Birnstiel, T.; Henning, Th.

doi:10.1088/0004-637x/766/1/8

Cited by 92 publications

(115 citation statements)

References 112 publications

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“…only small grains). Similar results are found by Akimkin et al (2013) who used a self-consistent chemical model including dust evolution. They also find that on average, column densities of neutral molecules (e.g.…”

Section: Chemical Structuresupporting

confidence: 87%

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The Gas Disk: Evolution and Chemistry

et al. 2016

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Protoplanetary disks are the birthplaces of planetary systems. The evolution of the star-disk system and the disk chemical composition determines the initial conditions for planet formation. Therefore a comprehensive understanding of the main physical and chemical processes in disks is crucial for our understanding of planet formation. We give an overview of the early evolution of disks, discuss the importance of the stellar high-energy radiation for disk evolution and describe the general thermal and chemical structure of disks. Finally we provide an overview of observational tracers of the gas component and disk winds.

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Section: Chemical Structuresupporting

confidence: 87%

“…Also the impact of turbulent mixing (e.g., Semenov et al 2006;Furuya and Aikawa 2014) or dust evolution (e.g. Vasyunin et al 2011;Akimkin et al 2013) can be studied with such models. An extensive and complete review of this kind of models can be found in Henning and Semenov (2013) and Dutrey et al (2014).…”

Section: Chemical Processing Of Disksmentioning

confidence: 99%

The Gas Disk: Evolution and Chemistry

et al. 2016

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“…In reality, the dust grains will have both a size distribution and variable dust-to-gas mass ratio caused by gravitational settling towards the midplane and dust-grain coagulation (grain growth). Several groups have also looked at the effects of dust-grain evolution on protoplanetary disk chemistry (see, e.g., Aikawa & Nomura 2006;Fogel et al 2011;Vasyunin et al 2011;Akimkin et al 2013). A parameterised treatment of grain growth affects the geometrical height of the molecular layer but appears to have little effect on the column densities of gas-phase molecules (Aikawa & Nomura 2006).…”

Section: Comparison With Other Modelsmentioning

confidence: 99%

Complex organic molecules in protoplanetary disks

Walsh

Millar

Nomura

et al. 2014

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356

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Context. Protoplanetary disks are vital objects in star and planet formation, possessing all the material, gas and dust, which may form a planetary system orbiting the new star. Small, simple molecules have traditionally been detected in protoplanetary disks; however, in the ALMA era, we expect the molecular inventory of protoplanetary disks to significantly increase. Aims. We investigate the synthesis of complex organic molecules (COMs) in protoplanetary disks to put constraints on the achievable chemical complexity and to predict species and transitions which may be observable with ALMA. Methods. We have coupled a 2D steady-state physical model of a protoplanetary disk around a typical T Tauri star with a large gas-grain chemical network including COMs. We compare the resulting column densities with those derived from observations and perform ray-tracing calculations to predict line spectra. We compare the synthesised line intensities with current observations and determine those COMs which may be observable in nearby objects. We also compare the predicted grain-surface abundances with those derived from cometary comae observations. Results. We find COMs are efficiently formed in the disk midplane via grain-surface chemical reactions, reaching peak grain-surface fractional abundances ∼10 −6 -10 −4 that of the H nuclei number density. COMs formed on grain surfaces are returned to the gas phase via non-thermal desorption; however, gas-phase species reach lower fractional abundances than their grain-surface equivalents, ∼10 −12 -10 −7 . Including the irradiation of grain mantle material helps build further complexity in the ice through the replenishment of grain-surface radicals which take part in further grain-surface reactions. There is reasonable agreement with several line transitions of H 2 CO observed towards T Tauri star-disk systems. There is poor agreement with HC 3 N lines observed towards LkCa 15 and GO Tau and we discuss possible explanations for these discrepancies. The synthesised line intensities for CH 3 OH are consistent with upper limits determined towards all sources. Our models suggest CH 3 OH should be readily observable in nearby protoplanetary disks with ALMA; however, detection of more complex species may prove challenging, even with ALMA "Full Science" capabilities. Our grain-surface abundances are consistent with those derived from cometary comae observations providing additional evidence for the hypothesis that comets (and other planetesimals) formed via the coagulation of icy grains in the Sun's natal disk.

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“…107,108 Several groups have investigated the influence of dust-grain evolution on disk chemistry. [109][110][111][112][113] The inclusion of grain growth tended to push the molecular layer deeper into the disk with increasing grain size; however, the vertical column densities of molecules remained unaffected. 110 Grain settling was found to lead to a smaller freeze out zone and a larger molecular layer due to the increased penetration of UV radiation.…”

Section: Comparison With Previous Disk Modelsmentioning

confidence: 99%

“…111 Recent models have coupled both dust evolution processes in a disk model with full gas-grain chemistry. 112,113 In these models the chemically stratified nature of the disk is retained, albeit with a molecular layer which resides deeper into the disk. Both works also found that the gas-phase column densities are enhanced (at the expense of the grain-surface column densities) relative to the results using pristine interstellar dust.…”

Section: Comparison With Previous Disk Modelsmentioning

confidence: 99%

Complex organic molecules along the accretion flow in isolated and externally irradiated protoplanetary disks

et al. 2014

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The birth environment of the Sun will have influenced the physical and chemical structure of the pre-solar nebula, including the attainable chemical complexity reached in the disk, important for prebiotic chemistry. The formation and distribution of complex organic molecules (COMs) in a disk around a T Tauri star is investigated for two scenarios: (i) an isolated disk, and (ii) a disk irradiated externally by a nearby massive star. The chemistry is calculated along the accretion flow from the outer disk inwards using a comprehensive network which includes gas-phase reactions, gas-grain interactions, and thermal grain-surface chemistry. Two simulations are performed, one beginning with complex ices and one with simple ices only. For the isolated disk, COMs are transported without major chemical alteration into the inner disk where they thermally desorb into the gas reaching an abundance representative of the initial assumed ice abundance. For simple ices, COMs can efficiently form on grain surfaces under the conditions in the outer disk. Gas-phase COMs are released into the molecular layer via photodesorption. For the irradiated disk, complex ices are also transported inwards; however, they undergo thermal processing caused by the warmer conditions in the irradiated disk which tends to reduce their abundance along the accretion flow. For simple ices, grain-surface chemistry cannot efficiently synthesise COMs in the outer disk because the necessary grain-surface radicals, which tend to be particularly volatile, are not sufficiently abundant on the grain surfaces. Gas-phase COMs are formed in the inner region of the irradiated disk via gas-phase chemistry induced by the desorption of strongly bound molecules such as methanol; hence, the abundances are not representative of the initial molecular abundances injected into the outer disk. These results suggest that the composition of comets formed in isolated disks may differ from those formed in externally irradiated disks with the latter composed of more simple ices.

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Protoplanetary Disk Structure With Grain Evolution: The Andes Model

Cited by 92 publications

References 112 publications

The Gas Disk: Evolution and Chemistry

The Gas Disk: Evolution and Chemistry

Complex organic molecules in protoplanetary disks

Complex organic molecules along the accretion flow in isolated and externally irradiated protoplanetary disks

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