The Effects of UV Continuum and Ly Radiation on the Chemical Equilibrium of T Tauri Disks
- 18 June 2003
- journal article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 591 (2) , L159-L162
- https://doi.org/10.1086/377148
Abstract
We show in this Letter that the spectral details of the FUV radiation fields have a large impact on the chemistry of protoplanetary disks surrounding T Tauri stars. We show that the strength of a realistic stellar FUV field is significantly lower than typically assumed in chemical calculations and that the radiation field is dominated by strong line emission, most notably Lyman alpha radiation. The effects of the strong Lyman alpha emission on the chemical equilibrium in protoplanetary disks has previously been unrecognized. We discuss the impact of this radiation on molecular observations in the context of a radiative transfer model that includes both direct attenuation and scattering. In particular, Lyman alpha radiation will directly dissociate water vapor and may contribute to the observed enhancements of CN/HCN in disks.Comment: 14 pages, 4 figures, accepted by ApJ LetterKeywords
All Related Versions
This publication has 33 references indexed in Scilit:
- Variability of Southern T Tauri Stars. II. The Spectral Variability of the Classical T Tauri Star TW HydraeThe Astrophysical Journal, 2002
- Warm molecular layers in protoplanetary disksAstronomy & Astrophysics, 2002
- Observations of T Tauri Stars usingHubble Space TelescopeGHRS. I. Far‐Ultraviolet Emission LinesThe Astrophysical Journal, 2002
- Two-dimensional distributions and column densities of gaseous molecules in protoplanetary disksAstronomy & Astrophysics, 2001
- Accretion Disks around Young Objects. III. Grain GrowthThe Astrophysical Journal, 2001
- Accretion Disks around Young Objects. II. Tests of Well‐mixed Models with ISM DustThe Astrophysical Journal, 1999
- The electronic spectrum of water in the discrete and continuum regions. Absolute optical oscillator strengths for photoabsorption (6–200 eV)Chemical Physics, 1993
- A powerful local shear instability in weakly magnetized disks. I - Linear analysis. II - Nonlinear evolutionThe Astrophysical Journal, 1991
- Monte Carlo calculations for resonance scattering with absorption or differential expansionThe Astrophysical Journal, 1979
- Photoelectric heating of interstellar gasThe Astrophysical Journal Supplement Series, 1978