Gas emission from debris disks around A and F stars

Abstract

Gas has been detected in a number of debris disk systems. This gas may have arisen from grain sublimation or grain photodesorption. It interacts with the surrounding dust grains through a number of charge and heat exchanges. Studying the chemical composition and physical state of this gas can therefore reveal much about the dust component in these debris disks. We have produced a new code, ontario, to address gas emission from dusty gas-poor disks around A--F stars. This code computes the gas ionization and thermal balance self-consistently, with particular care taken of heating/cooling mechanisms. Line emission spectra are then produced for each species (up to zinc) by statistical equilibrium calculations of the atomic/ionic energy levels. For parameters that resemble the observed beta Pictoris gas disk, we find that the gas is primarily heated by photoelectric emission from dust grains, and primarily cooled through the CII 157.7 micron line emission. The gas can be heated to a temperature that is warmer than that of the dust and may in some cases reach temperature for thermal escape. The dominant cooling line, CII 157.7 micron, should be detectable by Herschel in these disks, while the OI 63.2 micron line will be too faint. We also study the dependence of the cooling line fluxes on a variety of disk parameters, in light of the much improved sensitivity to thermal line emission in the mid/far infrared and at sub-millimeter wavelengths provided by, in particular, Herschel, SOFIA and ALMA. These new instruments will yield much new information about dusty debris disks.

18 pages, Accepted to ApJ

References in corpus (8)

• Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks
• The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk
• Formation and Evolution of Planetary Systems: Upper Limits to the Gas Mass in Disks Around Sun-like Stars
• Accretion Disks around Young Stars: Lifetimes, Disk Locking and Variability
• The Origins of Fluorescent H2 Emission From T Tauri~Stars
• The Dust and Gas Around beta Pictoris
• Modeling the gas-phase chemistry of the transitional disk around HD 141569A
• Formation of Narrow Dust Rings in Circumstellar Debris Disks

Cited by in corpus (19)

• Predictions for the secondary CO, C and O gas content of debris discs from the destruction of volatile-rich planetesimals
• GASPS - a Herschel survey of gas and dust in Protoplanetary Disks: Summary and Initial Statistics
• A self-consistent model for the evolution of the gas produced in the debris disc of $\beta$ Pictoris
• CO mass upper limits in the Fomalhaut ring - the importance of NLTE excitation in debris discs and future prospects with ALMA
• Molecular gas in young debris disks
• A CO survey in planet-forming disks: characterizing the gas content in the epoch of planet formation
• Herschel HIFI observations of ionised carbon in the β Pictoris debris disk
• ALMA resolves CI emission from the $\beta$ Pictoris debris disk
• Exposing the Gas Braking Mechanism of the beta Pictoris Disk
• Herschel detects oxygen in the beta Pictoris debris disk
• The magnetorotational instability in debris-disc gas
• Primordial or Secondary? Testing models of debris disk gas with ALMA
• On the unusual gas composition in the Beta Pictoris debris disk
• The Inner Debris Structure in the Fomalhaut Planetary System
• VLT imaging of the β Pictoris gas disk
• Polarization from Aligned Dust Grains in the $\beta$ Pic Debris Disk
• Circumstellar discs: What will be next?
• Physical conditions of gas components in debris disks of 49 Ceti and HD 21997
• Disentangling Planets from Photoelectric Instability in Gas-Rich Optically Thin Dusty Disks