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Tidal Downsizing model - III. Planets from sub-Earths to brown dwarfs: structure and metallicity preferences

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journal contribution
posted on 14.10.2015, 09:45 by Sergei Nayakshin, Mark Fletcher
We present population synthesis calculations of the Tidal Downsizing (TD) hypothesis for planet formation. Our models address the following observations: (i) most abundant planets being super-Earths; (ii) cores more massive than ∼5–15 M⊕ are enveloped by massive atmospheres; (iii) the frequency of occurrence of close-in gas-giant planets correlates strongly with metallicity of the host star; (iv) no such correlation is found for sub-Neptune planets; (v) presence of massive cores in giant planets; (vi) gas-giant planets are overabundant in metals compared to their host stars; (vii) this overabundance decreases with planet's mass; (viii) a deep valley in the planet mass function between masses of ∼10–20 M⊕ and ∼100 M⊕. A number of observational predictions distinguish the model from Core Accretion: (a) composition of the massive cores is always dominated by rocks not ices; (b) the core mass function is smooth with no minimum at ∼3 M⊕ and has no ice-dominated cores; (c) gas giants beyond 10 au are insensitive to the host-star metallicity; (d) objects more massive than ∼10 M[subscript: J] do not correlate or even anticorrelate with metallicity. The latter prediction is consistent with observations of low-mass stellar companions. TD can also explain formation of planets in close binary systems. TD model is a viable alternative to the Core Accretion scenario in explaining many features of the observed population of exoplanets.

History

Citation

Monthly Notices of the Royal Astronomical Society, 2015, 452 (2), pp. 1654-1676 (23)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Publisher

Oxford University Press (OUP)

issn

0035-8711

eissn

1365-2966

Acceptance date

16/06/2015

Copyright date

2015

Available date

14/10/2015

Publisher version

http://mnras.oxfordjournals.org/content/452/2/1654

Language

en