Connecting planet formation and astrochemistry

Cridland, Alex J.; Eistrup, Christian; Dishoeck, E. F. van

doi:10.1051/0004-6361/201834378

Cited by 64 publications

(96 citation statements)

References 71 publications

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“…Water has the highest sublimation temperature of all volatiles and hence within the water ice line the gas is "pristine", with little chemical evolution away from the initial volatile abundances in the disk. As outlined in Cridland et al (2019a) this result implies sub-stellar C/O since the protoplanetary disk gas is expected to have sub-solar C/O and the missing carbon is in the refractory material. Alternatively, Mordasini et al (2016) find sub-stellar C/O in the atmospheres of their synthetic planets because of the accretion of mostly icy solid bodies.…”

Section: Introductionmentioning

confidence: 76%

“…In this work, we extend the work of Cridland et al (2019a) by combining this carbon excess model to the astrochemical results for a range of protoplanetary disk models and the planet formation within those disks. In doing so we draw correlations between the underlying processes of planet formation and the resulting atmospheric C/O.…”

Section: Introductionmentioning

confidence: 97%

“…Hence there is a general disconnect between atmospheric C/O inferred observationally to be super-stellar and from the predictions of theory to be sub-stellar. Cridland et al (2019a) attempt to lessen this discrepancy by including an extra source of gaseous carbon, which is generated by the chemical processing of carbon-rich dust grains (Anderson et al 2017;Gail & Trieloff 2017;Klarmann et al 2018). That work finds that this excess carbon indeed improved the predictions of their theoretical model (with super-stellar C/O), if the chemical processes leading to the carbon excess was an ongoing process rather than a one-time release event.…”

Section: Introductionmentioning

confidence: 98%

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Connecting planet formation and astrochemistry

Cridland

Dishoeck

Alessi

et al. 2019

A&A

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To understand the role that planet formation history has on the observable atmospheric carbon-to-oxygen ratio (C/O) we have produced a population of astrochemically evolving protoplanetary disks. Based on the parameters used in a pre-computed population of growing planets, their combination allows us to trace the molecular abundances of the gas that is being collected into planetary atmospheres. We include atmospheric pollution of incoming (icy) planetesimals as well as the effect of refractory carbon erosion noted to exist in our own solar system. We find that the carbon and oxygen content of Neptune-mass planets are determined primarily through solid accretion and result in more oxygen-rich (by roughly two orders of magnitude) atmospheres than hot Jupiters, whose C/O are primarily determined by gas accretion. Generally we find a “main sequence” between the fraction of planetary mass accreted through solid accretion and the resulting atmospheric C/O; planets of higher solid accretion fraction have lower C/O. Hot Jupiters whose atmospheres have been chemically characterized agree well with our population of planets, and our results suggest that hot-Jupiter formation typically begins near the water ice line. Lower mass hot Neptunes are observed to be much more carbon rich (with 0.33 ≲ C/O ≲ 1) than is found in our models (C/O ~ 10−2), and suggest that some form of chemical processing may affect their observed C/O over the few billion years between formation and observation. Our population reproduces the general mass-metallicity trend of the solar system and qualitatively reproduces the C/O metallicity anti-correlation that has been inferred for the population of characterized exoplanetary atmospheres.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

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Connecting planet formation and astrochemistry

Cridland

Dishoeck

Alessi

et al. 2019

A&A

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“…Our used model also does not account for the formation of molecules during the infall stage, however simulations using solar-like composition (Furuya et al 2015) seem to be in agreement with our model at solar composition. However, the impact of a more advanced model seems to be much more profound on the gaseous component (Eistrup et al 2018) and thus the planetary atmosphere composition (Cridland et al 2019) than on the solid composition. However, to calculate the solid composition of the material, also the gaseous component has to be taken into account.…”

Section: Chemical Modelmentioning

confidence: 99%

Influence of sub- and super-solar metallicities on the composition of solid planetary building blocks

Bitsch

Battistini

2019

A&A

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The composition of the protoplanetary disc is thought to be linked to the composition of the host star, where a higher overall metallicity of the host star provides more building blocks for planets. However, most of the planet formation simulations only link the stellar iron abundance [Fe/H] to planet formation and the iron abundance in itself is used as a proxy to scale all elements. On the other hand, large surveys of stellar abundances show that this is not true. We use here stellar abundances from the GALAH surveys to determine the average detailed abundances of Fe, Si, Mg, O, and C for a broad range of host star metallicities with [Fe/H] spanning from -0.4 to +0.4. Using an equilibrium chemical model that features the most important rock forming molecules as well as volatile contributions of H 2 O, CO 2 , CH 4 and CO, we calculate the chemical composition of solid planetary building blocks around stars with different metallicities. Solid building blocks that are formed entirely interior to the water ice line (T>150K) only show an increase in Mg 2 SiO 4 and a decrease in MgSiO 3 for increasing host star metallicity, related to the increase of Mg/Si for higher [Fe/H]. Solid planetary building blocks forming exterior to the water ice line (T<150K), on the other hand, show dramatic changes in their composition. In particular the water ice content decreases from around ∼50% at [Fe/H]=-0.4 to ∼6% at [Fe/H]=0.4 in our chemical model. This is mainly caused by the increasing C/O ratio with increasing [Fe/H], which binds most of the oxygen in gaseous CO and CO 2 , resulting in a small water ice fraction. Planet formation simulations coupled with the chemical model confirm these results by showing that the water ice content of super-Earths decreases with increasing host star metallicity due to the increased C/O ratio. This decrease of the water ice fraction has important consequences for planet formation, planetary composition and the eventual habitability of planetary systems formed around these high metallicity stars.

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“…Modelling of the molecular composition of protoplanetary discs is thereby a useful tool for considering the composition of the building blocks of planet formation (e.g. Eistrup et al 2016;Bosman et al 2018;Cridland et al 2019;. Measurements of C/O and of metallicity (e.g.…”

Section: Introductionmentioning

confidence: 99%

The impact of pre-main sequence stellar evolution on mid-plane snowline locations and C/O in planet forming discs

Miley

Panić

Booth

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We investigate the impact of pre-main sequence stellar luminosity evolution on the thermal and chemical properties of disc midplanes. We create template disc models exemplifying initial conditions for giant planet formation for a variety of stellar masses and ages. These models include the 2D physical structure of gas as well as 1D chemical structure in the disc midplane. The disc temperature profiles are calculated using fully physically consistent radiative transfer models for stars between 0.5 and 3 M⊙ and ages up to 10 Myr. The resulting temperature profiles are used to determine how the chemical conditions in the mid-plane change over time. We therefore obtain gas and ice-phase abundances of the main carbon and oxygen carrier species. While the temperature profiles produced are not markedly different for the stars of different masses at early stages (≤1 Myr), they start to diverge significantly beyond 2 Myr. Discs around stars with mass ≥1.5 M⊙ become warmer over time as the stellar luminosity increases, whereas low-mass stars decrease in luminosity leading to cooler discs. This has an observable effect on the location of the CO snowline, which is located >200 au in most models for a 3 M⊙ star, but is always within 80 au for 0.5 M⊙ star. The chemical compositions calculated show that a well defined stellar mass and age range exists in which high C/O gas giants can form. In the case of the exoplanet HR8799b, our models show it must have formed before the star was 1 Myr old.

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Connecting planet formation and astrochemistry

Cited by 64 publications

References 71 publications

Connecting planet formation and astrochemistry

Connecting planet formation and astrochemistry

Influence of sub- and super-solar metallicities on the composition of solid planetary building blocks

The impact of pre-main sequence stellar evolution on mid-plane snowline locations and C/O in planet forming discs

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