CHEMICAL PROCESSES IN PROTOPLANETARY DISKS

By C. Walsh, T. Millar, Hideko Nomura Queen's University Belfast, K. University. 2010

145 citations recorded by the source corpus.

We have developed a high-resolution combined physical and chemical model of a protoplanetary disk surrounding a typical T Tauri star. Our aims were to use our model to calculate the chemical structure of disks on small scales (submilliarcsecond in the inner disk for objects at the distance of Taurus, ∼140 pc) to investigate the various chemical processes thought to be important in disks and to determine potential molecular tracers of each process. Our gas-phase network was extracted from the UMIST Database for Astrochemistry to which we added gas–grain interactions including freezeout and thermal and non-thermal desorption (cosmic-ray-induced desorption, photodesorption, and X-ray desorption), and a grain-surface network. We find that cosmic-ray-induced desorption has the least effect on our disk chemical structure while photodesorption has a significant effect, enhancing the abundances of most gas-phase molecules throughout the disk and affecting the abundances and distribution of HCN, CN, and CS, in particular. In the outer disk, we also see enhancements in the abundances of H2O and CO2. X-ray desorption is a potentially powerful mechanism in disks, acting to homogenize the fractional abundances of gas-phase species across the depth and increasing the column densities of most molecules, although there remain significant uncertainties in the rates adopted for this process. The addition of grain-surface chemistry enhances the fractional abundances of several small complex organic molecules including CH3OH, HCOOCH3, and CH3OCH3 to potentially observable values (i.e., a fractional abundance of ≳10−11).

Subfields: Astronomy and Astrophysics, Atmospheric Science, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/1882eb003a2453b2d3114b0757ff81478c2b202e

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. E. Bergin
2. D. Wilner
3. S. Andrews
4. P. Caselli
5. E. Herbst
6. A. Hughes
7. Cecilia Ceccarelli
8. K. Rosenfeld

In Atmospheric Science

1. E. Herbst
2. P. Caselli
3. E. Bergin
4. Y. Aikawa
5. Cecilia Ceccarelli
6. A. Bosman
7. Japan.
8. UK.

In Spectroscopy

1. E. Bergin
2. D. Wilner
3. S. Andrews
4. Cecilia Ceccarelli
5. P. Caselli
6. E. Herbst
7. A. Hughes
8. E. Chiang

Citations in the corpus

• Our astrochemical heritage (2012, background): “…turbulence mixing and disk winds (Hersant et al. 2009; Heinzeller et al. 2011), photochemistry and wavelength-dependent reaction cross sections (Walsh et al. 2012), comprehensive physical, chemical and radiative transfer modeling (Gorti and Hollenbach 2008; Woitke et al. 2010; Kamp et al.…”
• Photodissociation and photoionisation of atoms and molecules of astrophysical interest (2017, methodology): “These single-point time-dependent gas-phase models use the integration program of Walsh et al. (2009, 2010) to trace the chemical evolution of a range of atoms and molecules assuming a constant temperature, density, and visual extinction; and a set of initial abundances.”
• The molecular composition of the planet-forming regions of protoplanetary disks across the luminosity regime (2015, methodology): “Walsh et al. (2010) used a self-consistent model for the protoplanetary disk structure including the effects of heating by UV excess emission and X-rays (Nomura & Millar 2005; Nomura et al. 2007) and a chemical network similar in complexity to the work of Willacy & Woods (2009), excluding deuterium.”
• WEAK TURBULENCE IN THE HD 163296 PROTOPLANETARY DISK REVEALED BY ALMA CO OBSERVATIONS (2015, background): “3 q q q q mid mid0 atm atm0 0 1.3 ( ) ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎛ ⎝ ⎞ ⎠ ⎛ ⎝ ⎞ ⎠ ⎛ ⎝ ⎞ ⎠ = = = This type of profile for the vertical and radial temperature structure is consistent with detailed models of the gas (Jonkheid et al. 2007; Walsh et al. 2010) and the dust (D’Alessio et al. 2006).”
• EVIDENCE OF FAST PEBBLE GROWTH NEAR CONDENSATION FRONTS IN THE HL TAU PROTOPLANETARY DISK (2015, methodology): “…ices we define the condensation temperature of species i as that where the thermal desorption and accretion rates are equal, i.e., niice × k i desorp = n i gas × k i accr , (4) where kidesorp and k i accr are calculated using the treatment outlined in Woitke et al. (2009) and Walsh et al. (2010).”
• Complex organic molecules in protoplanetary disks (2013, methodology): “…of prebiotic chemistry; however, thus far, searches for gas-phase glycine towards hot cores have been unsuccessful (see, e.g., Snyder et al. 2005) In Walsh et al. (2010) and Walsh et al. (2012), henceforth referred to as WMN10 and WNMA12, we calculated the chemical composition of a protoplanetary…”