Uncertainties in water chemistry in disks: An application to TW Hydrae

Kamp, I.; Thi, Wing-Fai; Meeus, G.; Woitke, P.; Pinte, C.; Meijerink, R.; Spaans, Marco; Pascucci, Ilaria; Aresu, G.; Dent, W. R. F.

doi:10.1051/0004-6361/201220621

Cited by 58 publications

(82 citation statements)

References 97 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…That was also a conclusion of Kamp et al (2013). Under the conditions and assumptions presented here, the majority of changes to the chemical abundances take place between 0.5 and 7 Myr, and as in evident from Fig.…”

Section: Timescales Of Chemical Changessupporting

confidence: 77%

Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes

Eistrup

Walsh

Dishoeck

2018

A&A

150

252

View full text Add to dashboard Cite

Context. Exoplanet atmospheres are thought be built up from accretion of gas as well as pebbles and planetesimals in the midplanes of planet-forming disks. The chemical composition of this material is usually assumed to be unchanged during the disk lifetime. However, chemistry can alter the relative abundances of molecules in this planet-building material. Aims. To assess the impact of disk chemistry during the era of planet formation. This is done by investigating the chemical changes to volatile gases and ices in a protoplanetary disk midplane out to 30 AU for up to 7 Myr, considering a variety of different conditions, including a physical midplane structure that is evolving in time, and also considering two disks with different masses.Methods. An extensive kinetic chemistry gas-grain reaction network is utilised to evolve the abundances of chemical species over time. Two disk midplane ionisation levels (low and high) are explored, as well as two different makeups of the initial abundances ("inheritance" or "reset"). Results. Given a high level of ionisation, chemical evolution in protoplanetary disk midplanes becomes significant after a few times 10 5 yrs, and is still ongoing by 7 Myr between the H 2 O and the O 2 icelines. Inside the H 2 O iceline, and in the outer, colder regions of the disk midplane outside the O 2 iceline, the relative abundances of the species reach (close to) steady state by 7 Myr. Importantly, the changes in the abundances of the major elemental carbon and oxygen-bearing molecules imply that the traditional "stepfunction" for the C/O ratios in gas and ice in the disk midplane (as defined by sharp changes at icelines of H 2 O, CO 2 and CO) evolves over time, and cannot be assumed fixed, with the C/O ratio in the gas even becoming smaller than the C/O ratio in the ice. In addition, at lower temperatures (< 29 K), gaseous CO colliding with the grains gets converted into CO 2 and other more complex ices, lowering the CO gas abundance between the O 2 and CO thermal icelines. This effect can mimic a CO iceline at a higher temperature than suggested by its binding energy. Conclusions. Chemistry in the disk midplane is ionisation-driven, and evolves over time. This affects which molecules go into forming planets and their atmospheres. In order to reliably predict the atmospheric compositions of forming planets, as well as to relate observed atmospheric C/O ratios of exoplanets to where and how the atmospheres have formed in a disk midplane, chemical evolution needs to be considered and implemented into planet formation models.

show abstract

Section: Timescales Of Chemical Changessupporting

confidence: 77%

Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes

Eistrup

Walsh

Dishoeck

2018

A&A

150

252

View full text Add to dashboard Cite

show abstract

“…The plotted contours show the area where both the vertical and radial cumulative emission contribution function for a given line is between 12.5 and 87.5 % (the 25 % contour), or between 37.5 and 62.5 % (the 75 % contour). Kama et al (2016); (c) van der Wiel et al (2014); (d) Meeus et al (2013); (e) Panić et al (2010); ( f ) Fedele et al (2013b); (g) Qi et al (2004); (h) Fedele (2016); (i) Kamp et al (2013); ( j) Bergin et al (2013); (k) Favre et al (2013); (l) Thi et al (2004); (m) Thi et al (2010); (n) Fedele (in prep. ).…”

Section: Appendix B: Checking For Extended Emission Around Hd 100546mentioning

confidence: 98%

Volatile-carbon locking and release in protoplanetary disks

Kama

Bruderer

Dishoeck

et al. 2016

A&A

201

312

View full text Add to dashboard Cite

Aims. The composition of planetary solids and gases is largely rooted in the processing of volatile elements in protoplanetary disks. To shed light on the key processes, we carry out a comparative analysis of the gas-phase carbon abundance in two systems with a similar age and disk mass, but different central stars: HD 100546 and TW Hya. Methods. We combine our recent detections of C 0 in these disks with observations of other carbon reservoirs (CO, C + , C 2 H) and gas-mass and warm-gas tracers (HD, O 0 ), as well as spatially resolved ALMA observations and the spectral energy distribution. The disks are modelled with the DALI 2D physical-chemical code. Stellar abundances for HD 100546 are derived from archival spectra. Results. Upper limits on HD emission from HD 100546 place an upper limit on the total disk mass of ≤0.1 M . The gas-phase carbon abundance in the atmosphere of this warm Herbig disk is, at most, moderately depleted compared to the interstellar medium, with [C]/[H] gas = (0.1−1.5) × 10 −4 . HD 100546 itself is a λ Boötis star, with solar abundances of C and O but a strong depletion of rockforming elements. In the gas of the T Tauri disk TW Hya, both C and O are strongly underabundant, with [C]/[H] gas = (0.2−5.0)×10 −6 and C/O > 1. We discuss evidence that the gas-phase C and O abundances are high in the warm inner regions of both disks. Our analytical model, including vertical mixing and a grain size distribution, reproduces the observed [C]/[H] gas in the outer disk of TW Hya and allows to make predictions for other systems.

show abstract

“…We note that the total dust mass and the dust surface density profile are model dependent quantities with values that vary across the literature (Calvet et al 2002;Andrews & Williams 2005;Hughes et al 2008Hughes et al , 2011bKamp et al 2013;Hogerheijde et al 2016). We thus choose the Andrews et al (2012) model because it is based off of 870 μm emission, which is within the range of our dust line observations.…”

Section: Particle Growth and The Dust-to-gas Ratiomentioning

confidence: 99%

Using Ice and Dust Lines to Constrain the Surface Densities of Protoplanetary Disks

Powell

Murray-Clay

Schlichting

2017

ApJ

View full text Add to dashboard Cite

We present a novel method for determining the surface density of protoplanetary disks through consideration of disk "dust lines," which indicate the observed disk radial scale at different observational wavelengths. This method relies on the assumption that the processes of particle growth and drift control the radial scale of the disk at late stages of disk evolution such that the lifetime of the disk is equal to both the drift timescale and growth timescale of the maximum particle size at a given dust line. We provide an initial proof of concept of our model through an application to the disk TW Hya and are able to estimate the disk dust-to-gas ratio, CO abundance, and accretion rate in addition to the total disk surface density. We find that our derived surface density profile and dust-to-gas ratio are consistent with the lower limits found through measurements of HD gas. The CO ice line also depends on surface density through grain adsorption rates and drift and we find that our theoretical CO ice line estimates have clear observational analogues. We further apply our model to a large parameter space of theoretical disks and find three observational diagnostics that may be used to test its validity. First, we predict that the dust lines of disks other than TW Hya will be consistent with the normalized CO surface density profile shape for those disks. Second, surface density profiles that we derive from disk ice lines should match those derived from disk dust lines. Finally, we predict that disk dust and ice lines will scale oppositely, as a function of surface density, across a large sample of disks.

show abstract

Uncertainties in water chemistry in disks: An application to TW Hydrae

Cited by 58 publications

References 97 publications

Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes

Molecular abundances and C/O ratios in chemically evolving planet-forming disk midplanes

Volatile-carbon locking and release in protoplanetary disks

Using Ice and Dust Lines to Constrain the Surface Densities of Protoplanetary Disks

Contact Info

Product

Resources

About