The chemical history of molecules in circumstellar disks

Visser, R.; Doty, S. D.; Dishoeck, E. F. van

doi:10.1051/0004-6361/201117249

Cited by 145 publications

(200 citation statements)

References 98 publications

Supporting

Mentioning

193

Contrasting

Order By: Relevance

“…As a result, much of the material contained within the outer disk ( 10 AU) at the end of collapse consists primarily of "pristine" interstellar ice (see Fig. 4 in Visser et al 2011). Hence, beginning our simulations with initial molecular abundances representative of prestellar conditions is an appropriate assumption.…”

Section: Comparison With Other Modelsmentioning

confidence: 99%

Complex organic molecules in protoplanetary disks

Walsh

Millar

Nomura

et al. 2014

A&A

223

356

View full text Add to dashboard Cite

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.

show abstract

Section: Comparison With Other Modelsmentioning

confidence: 99%

Complex organic molecules in protoplanetary disks

Walsh

Millar

Nomura

et al. 2014

A&A

223

356

View full text Add to dashboard Cite

show abstract

“…After each burst ends, we follow the quiescent chemistry for a maximum of 10 5 yr to cover the full range of potential timescales from, e.g., Scholz et al (2013). The models are static and ignore any dynamical effects of the envelope collapsing and dissipating on typical timescales of a few 10 5 yr (Evans et al 2009;Visser et al 2011). …”

Section: Physical Frameworkmentioning

confidence: 99%

“…The second type is simple hydrogenation of C to CH 4 , N to NH 3 , and O to H 2 O. This happens one H atom at a time at a rate equal to the adsorption rate of H onto the grain surface multiplied by the relative fraction of the reactant molecule in the ice (Visser et al 2011). Conversion of CO ice into CO 2 ice, as proposed by Kim et al (2011Kim et al ( , 2012, is not included; see Sect.…”

Section: Chemical Networkmentioning

confidence: 99%

Chemical tracers of episodic accretion in low-mass protostars

Visser

Bergin

Jørgensen

2015

A&A

View full text Add to dashboard Cite

Aims. Accretion rates in low-mass protostars can be highly variable in time. Each accretion burst is accompanied by a temporary increase in luminosity, heating up the circumstellar envelope and altering the chemical composition of the gas and dust. This paper aims to study such chemical effects and discusses the feasibility of using molecular spectroscopy as a tracer of episodic accretion rates and timescales. Methods. We simulate a strong accretion burst in a diverse sample of 25 spherical envelope models by increasing the luminosity to 100 times the observed value. Using a comprehensive gas-grain network, we follow the chemical evolution during the burst and for up to 10 5 yr after the system returns to quiescence. The resulting abundance profiles are fed into a line radiative transfer code to simulate rotational spectra of C 18 O, HCO + , H 13 CO + , and N 2 H + at a series of time steps. We compare these spectra to observations taken from the literature and to previously unpublished data of HCO + and N 2 H + 6−5 from the Herschel Space Observatory. Results. The bursts are strong enough to evaporate CO throughout the envelope, which in turn enhances the abundance of HCO + and reduces that of N 2 H + . After the burst, it takes 10 3 -10 4 yr for CO to refreeze and for HCO + and N 2 H + to return to normal. The H 2 O snowline expands outwards by a factor of ∼10 during the burst; afterwards, it contracts again on a timescale of 10 2 -10 3 yr. The chemical effects of the burst remain visible in the rotational spectra for as long as 10 5 yr after the burst has ended, highlighting the importance of considering luminosity variations when analyzing molecular line observations in protostars. The spherical models are currently not accurate enough to derive robust timescales from single-dish observations. As follow-up work, we suggest that the models be calibrated against spatially resolved observations in order to identify the best tracers to be used for statistically significant source samples.

show abstract

“…The importance of the shock in influencing the composition of material that enters the disk is still a matter of debate (e.g. Lunine et al 1991;Visser et al 2009). …”

Section: Initial Stages and Chemistrymentioning

confidence: 99%

Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites

et al. 2015

View full text Add to dashboard Cite

Comets play a dual role in understanding the formation and evolution of the solar system. First, the composition of comets provides information about the origin of the giant planets and their moons because comets formed early and their composition is not expected to have evolved significantly since formation. They, therefore serve as a record of conditions during the early stages of solar system formation. Once comets had formed, their orbits were perturbed allowing them to travel into the inner solar system and impact the planets. In this way they contributed to the volatile inventory of planetary atmospheres. We review here how knowledge of comet composition up to the time of the Rosetta mission has contributed to understanding the formation processes of the giant planets, their moons and small icy bodies in the solar system. We also discuss how comets contributed to the volatile inventories of the giant and terrestrial planets.

show abstract

The chemical history of molecules in circumstellar disks

Cited by 145 publications

References 98 publications

Complex organic molecules in protoplanetary disks

Complex organic molecules in protoplanetary disks

Chemical tracers of episodic accretion in low-mass protostars

Constraints from Comets on the Formation and Volatile Acquisition of the Planets and Satellites

Contact Info

Product

Resources

About