A Constraint on the Amount of Hydrogen from the CO Chemistry in Debris Disks
arXiv:2303.11544 · doi:10.3847/1538-4357/acc524
Abstract
The faint CO gases in debris disks are easily dissolved into C by UV irradiation, while CO can be reformed via reactions with hydrogen. The abundance ratio of C/CO could thus be a probe of the amount of hydrogen in the debris disks. We conduct radiative transfer calculations with chemical reactions for debris disks. For a typical dust-to-gas mass ratio of debris disks, CO formation proceeds without the involvement of H because a small amount of dust grains makes H formation inefficient. We find that the CO to C number density ratio depends on a combination of , where is the hydrogen nucleus number density, is the metallicity, and is the FUV flux normalized by the Habing flux. Using an analytic formula for the CO number density, we give constraints on the amount of hydrogen and metallicity for debris disks. CO formation is accelerated by excited H either when the dust-to-gas mass ratio is increased or the energy barrier of chemisorption of hydrogen on the dust surface is decreased. This acceleration of CO formation occurs only when the shielding effects of CO are insignificant. In shielded regions, the CO fractions are almost independent of the parameters of dust grains.
arXiv comment29pages, 13figures, accepted for ApJ
References in corpus (67)
- The NumPy array: a structure for efficient numerical computation
- Disk Frequencies and Lifetimes in Young Clusters
- Structure of Stationary Photodissociation Fronts
- Infrared Emission from Interstellar Dust. I. Stochastic Heating of Small Grains
- The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks
- A model for atomic and molecular interstellar gas: The Meudon PDR code
- Photodissociation and photoionisation of atoms and molecules of astrophysical interest
- Photoevaporation of Circumstellar Disks by FUV, EUV and X-ray Radiation from the Central Star
- The global dust SED: Tracing the nature and evolution of dust with DustEM
- The Definitive Abundance of Interstellar Oxygen
- On the theory of disc photoevaporation
- Debris Disks: Structure, Composition, and Variability
- Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks
- Time-Evolution of Viscous Circumstellar Disks due to Photoevaporation by FUV, EUV and X-ray Radiation from the Central Star
- Disk Winds Driven by Magnetorotational Instability and Dispersal of Proto-Planetary Disks
- Photoprocesses in protoplanetary disks
- Molecular Gas Clumps from the Destruction of Icy Bodies in the Pictoris Debris Disk
- Volatile carbon locking and release in protoplanetary disks. A study of TW Hya and HD 100546
- STIS Coronagraphic Observations of Beta Pictoris
- Hydrocarbon emission rings in protoplanetary disks induced by dust evolution
- The Abundance of Interstellar Nitrogen
- The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk
- Surface chemistry in the interstellar medium - I - H2 formation by Langmuir-Hinshelwood and Eley-Rideal mechanisms
- The chemistry of vibrationally excited H2 in the interstellar medium
- Parameters of Herbig Ae/Be and Vega-type stars
- Compression and ablation of the photo-irradiated cloud the Orion Bar
- Predictions for the secondary CO, C and O gas content of debris discs from the destruction of volatile-rich planetesimals
- ALMA observations of the molecular gas in the debris disk of the 30 Myr old star HD 21997
- Models of Chemistry, Thermal Balance and Infrared Spectra from Intermediate-Aged Disks around G and K stars
- MHD Simulations of Global Accretion Disks with Vertical Magnetic Fields
- Exocometary gas structure, origin and physical properties around Pictoris through ALMA CO multi-transition observations
- Non-Equilibrium Photodissociation Regions: Ionization-Dissociation Fronts
- Survival of icy grains in debris discs. The role of photosputtering
- Structure of photodissociation fronts in star-forming regions revealed by observations of high-J CO emission lines with Herschel
- Surface chemistry in the Interstellar Medium II. formation on dust with random temperature fluctuations
- A self-consistent model for the evolution of the gas produced in the debris disc of Pictoris
- High Resolution HST-STIS Spectra of CI and CO in the Beta Pictoris Circumstellar Disk
- The penetration of FUV radiation into molecular clouds
- Braking the Gas in the beta Pictoris Disk
- A Resolved Molecular Gas Disk around the Nearby A Star 49 Ceti
- CO mass upper limits in the Fomalhaut ring - the importance of NLTE excitation in debris discs and future prospects with ALMA
- New limb-darkening coefficients and synthetic photometry for model-atmosphere grids at Galactic, LMC, and SMC abundances
- Warm Debris Disks Produced by Giant Impacts During Terrestrial Planet Formation
- A Systematic Study of the Final Masses of Gas Giant Planets
- Radiation hydrodynamics simulations of photoevaporation of protoplanetary disks II: Metallicity dependence of UV and X-ray photoevaporation
- Radial Surface Density Profiles of Gas and Dust in the Debris Disk around 49 Ceti
- Excitation of H in photodissociation regions as seen by Spitzer
- Herschel Observations of Gas and Dust in the Unusual 49 Ceti Debris Disk
- Monte Carlo simulations of H2 formation on stochastically heated grains
- The Carbon Monoxide Abundance in Comet 103P/Hartley during the EPOXI Flyby
- Imaging [CI] around HD 131835: reinterpreting young debris discs with protoplanetary disc levels of CO gas as shielded secondary discs
- The Solar Argon Abundance
- New millimeter CO observations of the gas-rich debris disks 49 Cet and HD 32297
- Herschel HIFI observations of ionised carbon in the β Pictoris debris disk
- ALMA resolves CI emission from the Pictoris debris disk
- Molecular reconnaissance of the Pictoris gas disk with the SMA: a low HCN/(CO+CO) outgassing ratio and predictions for future surveys
- X-ray Ionization of Heavy Elements Applied to Protoplanetary Disks
- Detection of submillimeter-wave [C I] emission in gaseous debris disks of 49 Ceti and Beta Pictoris
- Photoevaporation of Grain-Depleted Protoplanetary Disks around Intermediate-Mass Stars: Investigating Possibility of Gas-Rich Debris Disks as Protoplanetary Remnants
- Debris disc formation induced by planetary growth
- Incorporation of stochastic chemistry on dust grains in the PDR code using moment equations
- Line emission from circumstellar disks around A stars
- First sub-arcsecond submillimeter-wave [C I] image of 49 Ceti with ALMA
- HI-to-H Transitions in Dust-Free Interstellar Gas
- The role of highly vibrationally excited H2 initiating the N chemistry: Quantum study and 3-sigma detection of NH emission in the Orion Bar PDR
- Quantum study of reaction O(3P) + H2(v,j) OH + H: OH formation in strongly UV-irradiated gas
- Physical conditions of gas components in debris disks of 49 Ceti and HD 21997