CO/H2 Abundance Ratio ~ 10^{-4} in a Protoplanetary Disk

Abstract

The relative abundances of atomic and molecular species in planet-forming disks around young stars provide important constraints on photochemical disk models and provide a baseline for calculating disk masses from measurements of trace species. A knowledge of absolute abundances, those relative to molecular hydrogen (H2), are challenging because of the weak rovibrational transition ladder of H${}_2$ and the inability to spatially resolve different emission components within the circumstellar environment. To address both of these issues, we present new contemporaneous measurements of CO and H2 absorption through the "warm molecular layer" of the protoplanetary disk around the Classical T Tauri Star RW Aurigae A. We use a newly commissioned observing mode of the Hubble Space Telescope-Cosmic Origins Spectrograph to detect warm H2 absorption in this region for the first time. An analysis of the emission and absorption spectrum of RW Aur shows components from the accretion region near the stellar photosphere, the molecular disk, and several outflow components. The warm H2 and CO absorption lines are consistent with a disk origin. We model the 1092-1117A spectrum of RW Aur to derive log10 N(H2)~=~19.90${}_{-0.22}^{+0.33}$ at T${}_{rot}$(H2) ~=~440~+/-~39 K. The CO $A$~--~$X$ bands observed from 1410-1520A are best fit by log10 N(CO)~=~16.1~${}_{-0.5}^{+0.3}$ at T${}_{rot}$(CO) ~=~200${}_{-125}^{+650}$ K. Combining direct measurements of the HI, H2, and CO column densities, we find a molecular fraction in the warm disk surface of $f_{H2}$~>=~0.47 and derive a molecular abundance ratio of CO/H2~=~1.6${}_{-1.3}^{+4.7}$~x~10${}^{-4}$, both consistent with canonical interstellar dense cloud values.

arXiv commentApJ - accepted. 13 pages, 8 figures

References in corpus (70)

• The effects of snowlines on C/O in planetary atmospheres
• Towards a Deterministic Model of Planetary Formation I: a Desert in the Mass and Semi Major Axis Distributions of Extra Solar Planets
• Circumstellar Dust Disks in Taurus-Auriga: The Submillimeter Perspective
• Extrasolar planet population synthesis I: Method, formation tracks and mass-distance distribution
• Observational Constraints on the Formation and Evolution of Binary Stars
• Spitzer Space Telescope study of disks in the young $\sigma$ Orionis cluster
• The Cosmic Origins Spectrograph
• An Optical Spectroscopic Study of T Tauri Stars. I. Photospheric Properties
• Timescale of Mass Accretion in Pre-Main-Sequence Stars
• Radiation thermo-chemical models of protoplanetary disks I. Hydrostatic disk structure and inner rim
• An Old Disk That Can Still Form a Planetary System
• A FUSE Survey of Interstellar Molecular Hydrogen in Translucent Clouds
• The Compositional Diversity of Extrasolar Terrestrial Planets: I. In-Situ Simulations
• Ultraviolet Survey of CO and H_2 in Diffuse Molecular Clouds: The Reflection of Two Photochemistry Regimes in Abundance Relationships
• Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra
• Survival of molecular gas in cavities of transition disks (I. CO)
• Organic molecules in protoplanetary disks around TTauri and HerbigAe stars
• A Spitzer Survey of Mid-Infrared Molecular Emission from Protoplanetary Disks II: Correlations and LTE Models
• A Significantly Low CO Abundance Toward the TW Hya Protoplanetary Disk: A Path to Active Carbon Chemistry?
• HST/COS Observations of the Ly alpha Forest toward the BL Lac Object 1ES1553+113
• The Far-Ultraviolet Spectra of TW Hya. II. Models of H2 Fluorescence in a Disk
• The structure and dynamics of molecular gas in planet-forming zones: A CRIRES spectro-astrometric survey
• Close Companions to Young Stars. I. A Large Spectroscopic Survey in Chamaeleon I and Taurus-Auriga
• VLBA determination of the distance to nearby star-forming regions II. Hubble 4 and HDE 283572 in Taurus
• Direct Measurement of the Ratio of Carbon Monoxide to Molecular Hydrogen in the Diffuse Interstellar Medium
• Predictions for the frequency and orbital radii of massive extrasolar planets
• The chemical history of molecules in circumstellar disks. II. Gas-phase species
• Formation and Evolution of Planetary Systems: Upper Limits to the Gas Mass in Disks Around Sun-like Stars
• HST/STIS Observations of the Bipolar Jet from RW Aurigae: Tracing Outflow Asymmetries Close to the Source
• Accretion Disks around Young Stars: Lifetimes, Disk Locking and Variability
• c2d Spitzer IRS Spectra of Disks around T Tauri Stars. III. [Ne II], [Fe I], and H_2 gas-phase lines
• VLT-CRIRES Survey of Rovibrational CO Emission from Protoplanetary Disks
• Young Stellar Objects in Lynds 1641: Disks, Accretion, and Star Formation History
• Evolution of Molecular Abundance in Protoplanetary Disks
• Massive planet migration: Theoretical predictions and comparison with observations
• Spatially Resolved Molecular Hydrogen Emission in the Inner 200AU Environments of Classical T Tauri Stars
• A Hubble Space Telescope Survey of H2 Emission in the Circumstellar Environments of Young Stars
• Hot Gas Lines in T Tauri Stars
• CO J=6-5 observations of TW Hya with the SMA
• Observations of T-Tauri Stars using HST-GHRS: I. Far Ultraviolet Emission Lines
• Orbital migration and the frequency of giant planet formation
• Near-Infrared Interferometric, Spectroscopic, and Photometric Monitoring of T Tauri Inner Disks
• N(H I)/E(B-V)
• High-resolution Ultraviolet Radiation Fields of Classical T Tauri Stars
• The loopy UV line profiles of RU Lupi: accretion, outflows, and fluorescence
• Mass ratios of the components in T Tauri binary systems and implications for multiple star formation
• Lyman alpha dominance of the Classical T Tauri FUV Radiation Field
• Evolution of X-ray and FUV Disk-Dispersing Radiation Fields
• FUSE and HST STIS Observations of Hot and Cold Gas in the AB Aurigae System
• Molecular Hydrogen Optical Depth Templates for FUSE Data Analysis
• Mapping the Circumstellar Environment of T Tauri with Fluorescent H_2 Emission
• HST/STIS observations of the RW Aurigae bipolar jet: mapping the physical parameters close to the source
• A Search for Mid-Infrared Molecular Hydrogen Emission from Protoplanetary Disks
• Looking for Pure Rotational H_2 Emission from Protoplanetary Disks
• The TEXES Survey For H2 Emission From Protoplanetary Disks
• The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems II: CO Fourth Positive Emission and Absorption
• FUV and X-ray irradiated protoplanetary disks: a grid of models I. The disk structure
• Quiescent H2 Emission From Pre-Main Sequence Stars in Chamaeleon I
• The Spatial Distribution of Fluorescent H${}_2$ Near T Tau
• Molecular hydrogen in the circumstellar environments of Herbig Ae/Be stars probed by FUSE
• The Far-Ultraviolet "Continuum" in Protoplanetary Disk Systems I: Electron-Impact H2 and Accretion Shocks
• Direct Measurement of Interstellar Extinction Toward Young Stars Using Atomic Hydrogen Lyman-$\alpha$ Absorption
• Far-UV sensitivity of the Cosmic Origins Spectrograph
• Characterizing CO Fourth Positive Emission in Young Circumstellar Disks
• CO and H2 Absorption in the AA Tauri Circumstellar Disk
• HST FUV imaging of DG Tau: Fluorescent molecular hydrogen emission from the wide angle outflow
• Adaptive Optics Echelle Spectroscopy of [Fe II] 1.644 um in the RW Aur Jet: A Narrow Slice Down the Axis of the Flow
• HST/COS Spectra of DF Tau and V4046 SGR: First Detection of Molecular Hydrogen Absorption Against the Ly$\alpha$ Emission Line
• Probing the Inner Regions of Protoplanetary Disks with CO Absorption Line Spectroscopy
• Where is the warm H2 ? A search for H2 emission from disks around Herbig Ae/Be stars

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