Resolving the chemistry in the disk of TW Hydrae I. Deuterated species

Abstract

We present Submillimeter Array (SMA) observations of several deuterated species in the disk around the classical T Tauri star TW Hydrae at arcsecond scales, including detections of the DCN J=3-2 and DCO+ J=3-2 lines, and upper limits to the HDO 3(1,2)-2(2,1), ortho-H2D+ 1(1,0)-1(1,1) and para-D2H+ 1(1,0)-1(0,1) transitions. We also present observations of the HCN J=3-2, HCO+ J=3-2 and H13CO+ J=4-3 lines for comparison with their deuterated isotopologues. We constrain the radial and vertical distributions of various species in the disk by fitting the data using a model where the molecular emission from an irradiated accretion disk is sampled with a 2D Monte Carlo radiative transfer code. We find that the distribution of DCO+ differs markedly from that of HCO+. The D/H ratios inferred change by at least one order of magnitude (0.01 to 0.1) for radii <30 AU to >70 AU and there is a rapid falloff of the abundance of DCO+ at radii larger than 90 AU. Using a simple analytical chemical model, we constrain the degree of ionization, x(e-)=n(e-)/n(H2), to be ~10^-7 in the disk layer(s) where these molecules are present. Provided the distribution of DCN follows that of HCN, the ratio of DCN to HCN is determined to be 1.7\pm0.5 \times 10^-2; however, this ratio is very sensitive to the poorly constrained vertical distribution of HCN. The resolved radial distribution of DCO+ indicates that {\it in situ} deuterium fractionation remains active within the TW Hydrae disk and must be considered in the molecular evolution of circumstellar accretion disks.

arXiv comment12 pages, 12 figures, accepted to ApJ

References in corpus (18)

• An atomic and molecular database for analysis of submillimetre line observations
• The Submillimeter Array
• Evidence for a developing gap in a 10 Myr old protoplanetary disk
• Warm Molecular Layers in Protoplanetary Disks
• Organic molecules in protoplanetary disks around TTauri and HerbigAe stars
• Abundant H2D+ in the pre-stellar core L1544
• Imaging the Disk around TW Hya with the Submillimeter Array
• Detection of D2H+ in the Dense Interstellar Medium
• Millimeter imaging of HD 163296: probing the disk structure and kinematics
• Physical and Chemical Structure of Protoplanetary Disks with Grain Growth
• The chemistry of multiply deuterated molecules in protoplanetary disks. I. The outer disk
• Detection of interstellar H_2D^+ emission
• CO J=6-5 observations of TW Hya with the SMA
• Deuterated molecules as a probe of ionization fraction in dense interstellar clouds
• Detection of DCO+ in a circumstellar disk
• Deuterated H${}_3^{+}$ in proto-planetary disks
• Deuterated molecules in DM Tau: DCO+, but no HDO
• Discovery of deuterated water in a young proto-planetary disk

Cited by in corpus (89)

• Protoplanetary Disks and Their Evolution
• Our astrochemical heritage
• 2021 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• 2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• Radiation thermo-chemical models of protoplanetary disks I. Hydrostatic disk structure and inner rim
• Imaging of the CO Snow Line in a Solar Nebula Analog
• Molecules with ALMA at Planet-forming Scales (MAPS) I: Program Overview and Highlights
• A Three-Dimensional View of Turbulence: Constraints on Turbulent Motions in the HD 163296 Protoplanetary Disk using DCO${}^{+}$
• The TW Hya Disk at 870 microns: Comparison of CO and Dust Radial Structures
• A Parametric Modeling Approach to Measuring the Gas Masses of Circumstellar Disks
• The cometary composition of a protoplanetary disk as revealed by complex cyanides
• Complex organic molecules in protoplanetary disks
• Constraining the X-ray and Cosmic Ray Ionization Chemistry of the TW Hya Protoplanetary Disk: Evidence for a Sub-interstellar Cosmic Ray Rate
• A Millimeter Continuum Size-Luminosity Relationship for Protoplanetary Disks
• Chemical Processes in Protoplanetary Disks
• Chemical evolution of turbulent protoplanetary disks and the Solar nebula
• The structure and dynamics of molecular gas in planet-forming zones: A CRIRES spectro-astrometric survey
• 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
• Empirical Constraints on Turbulence in Protoplanetary Accretion Disks
• CO and dust properties in the TW Hya disk from high-resolution ALMA observations
• Resolving the CO Snow Line in the Disk around HD 163296
• A Survey of CH3CN and HC3N in Protoplanetary Disks
• The polarimetric imaging mode of VLT/SPHERE/IRDIS I: Description, data reduction and observing strategy
• The 0.5-2.22-micron Scattered Light Spectrum of the Disk Around TW Hya: Detection of a Partially Filled Disk Gap at 80 AU
• ALMA imaging of the CO snowline of the HD 163296 disk with DCO+
• ALMA Observations of a Gap and a Ring in the Protoplanetary Disk around TW Hya
• The Structure of the Evolved Circumbinary Disk around V4046 Sgr
• Deuterium chemistry in protoplanetary disks II The inner 30 AU
• H2CO and N2H+ in Protoplanetary Disks: Evidence for a CO-ice Regulated Chemistry
• New extended deuterium fractionation model: assessment at dense ISM conditions and sensitivity analysis
• An ALMA survey of DCN/H${}^{13}$CN and DCO${}^{+}$/H${}^{13}$CO${}^{+}$ in protoplanetary disks
• Exclusion of Cosmic Rays in Protoplanetary Disks. II. Chemical Gradients and Observational Signatures
• Chemo-dynamical deuterium fractionation in the early solar nebula: The origin of water on Earth and in asteroids and comets
• The GALEX Nearby Young-Star Survey
• Chemistry in Disks. III. -- Photochemistry and X-ray driven chemistry probed by the ethynyl radical (CCH) in DM Tau, LkCa 15, and MWC 480
• Double DCO+ rings reveal CO ice desorption in the outer disk around IM Lup
• Volatile snowlines in embedded disks around low-mass protostars
• First detection of c-C3H2 in a circumstellar disk
• Chemistry in Disks. IX. Observations and modeling of HCO+ and DCO+ in DM Tau
• Chemistry in Disks. V: CN and HCN in proto-planetary disks
• First detection of H${}_2$S in a protoplanetary disk. The dense GG Tau A ring
• Subarcsecond Imaging of the NGC 6334 I(N) Protocluster: Two Dozen Compact Sources and a Massive Disk Candidate
• DCO${}^{+}$, DCN and N${}_2$D${}^{+}$ reveal three different deuteration regimes in the disk around the Herbig Ae star HD163296
• The chemistry of disks around T Tauri and Herbig Ae/Be stars
• Analytical Formulas of Molecular Ion Abundances and N2H+ Ring in Protoplanetary Disks
• Chemistry in a gravitationally unstable protoplanetary disc
• An evolutionary study of volatile chemistry in protoplanetary disks
• Imaging the Molecular Disk Orbiting the Twin Young Suns of V4046 Sgr
• The composition of the protosolar disk and the formation conditions for comets
• Nitrogen Fractionation in Protoplanetary Disks from the H13CN/HC15N Ratio
• Unbiased mm-wave Line Surveys of TW Hya and V4046 Sgr: The Enhanced C2H and CN Abundances of Evolved Protoplanetary Disks
• Molecules in the disk orbiting the twin young suns of V4046 Sgr
• H2CO distribution and formation in the TW Hya disk
• Evidence for Multiple Pathways to Deuterium Enhancements in Protoplanetary Disks
• Probing midplane CO abundance and gas temperature with DCO${}^{+}$ in the protoplanetary disk around HD 169142
• A Ring of C2H in the Molecular Disk Orbiting TW Hya
• Effects of accretion flow on the chemical structure in the inner regions of protoplanetary disks
• Evidence for DCO+ as a probe of ionization in the warm disk surface
• Multiple paths of deuterium fractionation in protoplanetary disks
• Chemistry of TMC-1 with multiply deuterated species and spin chemistry of H2, H2+, H3+ and their isotopologues
• Complex organic molecules along the accretion flow in isolated and externally irradiated protoplanetary disks
• Molecular content of the circumstellar disk in AB Aur: First detection of SO in a circumstellar disk
• Continuum and line modeling of disks around young stars II. Line diagnostics for GASPS from the DENT grid
• The TW Hya Rosetta Stone Project I: Radial and vertical distributions of DCN and DCO+
• Odin observations of water in molecular outflows and shocks
• Measuring elemental abundance ratios in protoplanetary disks at millimeter wavelengths
• Detection of HC18O+ in a protoplanetary disk: exploring oxygen isotope fractionation of CO
• A deep search for H2D+ in protoplanetary disks
• Detection of N${}_2$D${}^{+}$ in a protoplanetary disk
• The TW Hya Rosetta Stone Project IV: A hydrocarbon rich disk atmosphere
• Chemical composition of the circumstellar disk around AB Aurigae
• Molecules in the transition disk orbiting T Cha
• H${}_2$S observations in young stellar disks in Taurus
• Constraining accretion signatures of exoplanets in the TW Hya transitional disk
• Measuring Organic Molecular Emission in Disks with Low Resolution Spitzer Spectroscopy
• Modeling Nitrogen Fractionation in the Protoplanetary Disk around TW Hya: Model Constraints on Grain Population and Carbon-to-Oxygen Elemental Abundance Ratio
• Insights into planet formation from debris disks: I. The solar system as an archetype for planetesimal evolution
• Exploring DCO${}^{+}$ as a tracer of thermal inversion in the disk around the Herbig Ae star HD163296
• An SMA Survey of Chemistry in Disks around Herbig AeBe Stars
• Cold Deuterium Fractionation in the Nearest Planet-Forming Disk
• X-ray induced deuterium enrichment on N-rich organics in protoplanetary disks: an experimental investigation using synchrotron light
• The Synthetic ALMA Multiband Analysis of the Dust Properties of the TW Hya Protoplanetary Disk
• Using deuterated H3+ and other molecular species to understand the formation of stars and planets
• Molecules with ALMA at Planet-forming Scales (MAPS) XIX. Spiral Arms, a Tail, and Diffuse Structures Traced by CO around the GM Aur Disk
• Chemical evolution of a protoplanetary disk
• Protoplanetary Disk Chemistry
• The effect of carbon grain destruction on the chemical structure of protoplanetary disks