The effect of carbon grain destruction on the chemical structure of protoplanetary disks

Abstract

The bulk composition of the Earth is dramatically carbon poor compared to that of the interstellar medium, and this phenomenon extends to the asteroid belt. To interpret this carbon deficit problem, the carbonaceous component in grains must have been converted into the gas-phase in the inner regions of protoplanetary disks prior to planetary formation. We examine the effect of carbon grain destruction on the chemical structure of disks by calculating the molecular abundances and distributions using a comprehensive chemical reaction network. When carbon grains are destroyed and the elemental abundance of the gas becomes carbon-rich, the abundances of carbon-bearing molecules, such as HCN and carbon-chain molecules, increase dramatically near the midplane, while oxygen-bearing molecules, such as H${}_2$O and CO${}_2$, are depleted. We compare the results of these model calculations with the solid carbon fraction in the solar system. Although we find a carbon depletion gradient, there are some quantitative discrepancies: the model shows a higher value at the position of asteroid belt and a lower value at the location of the Earth. In addition, using the obtained molecular abundances distributions, coupled with line radiative transfer calculations, we make predictions for ALMA to potentially observe the effect of carbon grain destruction in nearby protoplanetary disks. The results indicate that HCN, H${}^{13}$CN and c-C${}_3$H${}_2$ may be good tracers.

arXiv comment31 pages, 21 figures, Accepted for publication in The Astrophysical Journal

References in corpus (59)

• The chemical composition of the Sun
• Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
• Interstellar Dust Grains
• An atomic and molecular database for analysis of submillimetre line observations
• The UMIST database for astrochemistry 2012
• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• The Origin of T Tauri X-ray Emission: New Insights from the Chandra Orion Ultradeep Project
• A Reappraisal of the Solar Photospheric C/O Ratio
• X-Ray Spectroscopy of Stars
• Solar System Abundances of the Elements
• The cometary composition of a protoplanetary disk as revealed by complex cyanides
• Complex organic molecules in protoplanetary disks
• Photoprocesses in protoplanetary disks
• H2O and OH gas in the terrestrial planet-forming zones of protoplanetary disks
• A Spitzer survey of mid-infrared molecular emission from protoplanetary disks I: Detection rates
• Organic molecules in protoplanetary disks around TTauri and HerbigAe stars
• First detection of gas-phase methanol in a protoplanetary disk
• Tracing the Ingredients for a Habitable Earth from Interstellar Space through Planet Formation
• Chemical Processes in Protoplanetary Disks
• The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime
• The Different Evolution of Gas and Dust in Disks around Sun-like and Cool Stars
• Chemical evolution of turbulent protoplanetary disks and the Solar nebula
• Hydrocarbon emission rings in protoplanetary disks induced by dust evolution
• Setting the volatile composition of (exo)planet-building material. Does chemical evolution in disk midplanes matter?
• Molecular Hydrogen Emission from Protoplanetary Disks II. Effects of X-ray Irradiation and Dust Evolution
• Disk Imaging Survey of Chemistry with SMA: II. Southern Sky Protoplanetary Disk Data and Full Sample Statistics
• Disk Imaging Survey of Chemistry with SMA (DISCS): I. Taurus Protoplanetary Disk Data
• Chemical Processes in Protoplanetary Disks II. On the importance of photochemistry and X-ray ionization
• Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids
• Hot H2O Emission and Evidence for Turbulence in the Disk of a Young Star
• Mass inventory of the giant-planet formation zone in a solar nebula analog
• Hot Organic Molecules Toward a Young Low-Mass Star: A Look at Inner Disk Chemistry
• Molecular Hydrogen Emission from Protoplanetary Disks
• Reprocessing of Ices in Turbulent Protoplanetary Disks: Carbon and Nitrogen Chemistry
• Resolving the chemistry in the disk of TW Hydrae I. Deuterated species
• GASPS - a Herschel survey of gas and dust in Protoplanetary Disks: Summary and Initial Statistics
• Carbon isotope fractionation in protoplanetary disks
• Resolving the CO Snow Line in the Disk around HD 163296
• A Survey of CH3CN and HC3N in Protoplanetary Disks
• First Detection of the Simplest Organic Acid in a Protoplanetary Disk
• The chemistry of multiply deuterated molecules in protoplanetary disks. I. The outer disk
• Two-dimensional Distributions and Column Densities of Gaseous Molecules in Protoplanetary Disks II
• The Distribution and Excitation of CH${}_3$CN in a Solar Nebula Analog
• An ALMA survey of DCN/H${}^{13}$CN and DCO${}^{+}$/H${}^{13}$CO${}^{+}$ in protoplanetary disks
• Water in Protoplanetary Disks: Deuteration and Turbulent Mixing
• X-ray Study of the Intermediate-Mass Young Stars Herbig Ae/Be Stars
• First detection of c-C3H2 in a circumstellar disk
• The Solar Nebula on Fire: A Solution to the Carbon Deficit in the Inner Solar System
• Detection of DCO+ in a circumstellar disk
• Chemistry in Disks. V: CN and HCN in proto-planetary disks
• Destruction of Refractory Carbon in Protoplanetary Disks
• Warm HCN, C2H2, and CO in the disk of GV Tau
• Nitrogen Fractionation in Protoplanetary Disks from the H13CN/HC15N Ratio
• Exploring the Origins of Deuterium Enrichments in Solar Nebular Organics
• Candidate Water Vapor Lines to Locate the H${}_2$O Snowline through High-Dispersion Spectroscopic Observations II. The Case of a Herbig Ae Star
• Candidate Water Vapor Lines to Locate the H${}_2$O Snowline through High-Dispersion Spectroscopic Observations I. The Case of a T Tauri Star
• Multiple paths of deuterium fractionation in protoplanetary disks
• Formation of cometary O${}_2$ ice and related ice species on grain surfaces in the midplane of the pre-Solar nebula

Cited by in corpus (3)

• Breaking Degeneracies in Formation Histories by Measuring Refractory Content in Gas Giants
• Chemical Evolution in a Protoplanetary Disk within Planet Carved Gaps and Dust Rings
• High Spatial Resolution Observations of Molecular Lines towards the Protoplanetary Disk around TW Hya with ALMA