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Planet population synthesis driven by pebble accretion in cluster environments

Ndugu, N.; Bitsch, B. LU and Jurua, E. (2018) In Monthly Notices of the Royal Astronomical Society 474(1). p.886-897
Abstract

The evolution of protoplanetary discs embedded in stellar clusters depends on the age and the stellar density in which they are embedded. Stellar clusters of young age and high stellar surface density destroy protoplanetary discs by external photoevaporation and stellar encounters. Here, we consider the effect of background heating from newly formed stellar clusters on the structure of protoplanetary discs and how it affects the formation of planets in these discs. Our planet formation model is built on the core accretion scenario, where we take the reduction of the core growth time-scale due to pebble accretion into account. We synthesize planet populations that we compare to observations obtained by radial velocity measurements. The... (More)

The evolution of protoplanetary discs embedded in stellar clusters depends on the age and the stellar density in which they are embedded. Stellar clusters of young age and high stellar surface density destroy protoplanetary discs by external photoevaporation and stellar encounters. Here, we consider the effect of background heating from newly formed stellar clusters on the structure of protoplanetary discs and how it affects the formation of planets in these discs. Our planet formation model is built on the core accretion scenario, where we take the reduction of the core growth time-scale due to pebble accretion into account. We synthesize planet populations that we compare to observations obtained by radial velocity measurements. The giant planets in our simulations migrate over large distances due to the fast type-II migration regime induced by a high disc viscosity (α = 5.4 × 10-3). Cold Jupiters (rp > 1 au) originate preferably from the outer disc, due to the large-scale planetary migration, while hot Jupiters (rp < 0.1 au) preferably form in the inner disc. We find that the formation of gas giants via pebble accretion is in agreement with the metallicity correlation, meaning that more gas giants are formed at larger metallicity. However, our synthetic population of isolated stars host a significant amount of giant planets even at low metallicity, in contradiction to observations where giant planets are preferably found around high metallicity stars, indicating that pebble accretion is very efficient in the standard pebble accretion framework. On the other hand, discs around stars embedded in cluster environments hardly form any giant planets at low metallicity in agreement with observations, where these changes originate from the increased temperature in the outer parts of the disc, which prolongs the core accretion time-scale of the planet. We therefore conclude that the outer disc structure and the planet's formation location determines the giant planet occurrence rate and the formation efficiency of cold and hot Jupiters.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Accretion, Accretion discs, Planets and satellites: formation, Protoplanetary discs
in
Monthly Notices of the Royal Astronomical Society
volume
474
issue
1
pages
12 pages
publisher
OXFORD UNIV PRESS
external identifiers
  • scopus:85044750153
ISSN
0035-8711
DOI
10.1093/mnras/stx2815
language
English
LU publication?
yes
id
f6d479f3-4470-41ee-b6d5-f2ad8659b0a1
date added to LUP
2018-05-22 07:46:35
date last changed
2018-10-07 05:06:38
@article{f6d479f3-4470-41ee-b6d5-f2ad8659b0a1,
  abstract     = {<p>The evolution of protoplanetary discs embedded in stellar clusters depends on the age and the stellar density in which they are embedded. Stellar clusters of young age and high stellar surface density destroy protoplanetary discs by external photoevaporation and stellar encounters. Here, we consider the effect of background heating from newly formed stellar clusters on the structure of protoplanetary discs and how it affects the formation of planets in these discs. Our planet formation model is built on the core accretion scenario, where we take the reduction of the core growth time-scale due to pebble accretion into account. We synthesize planet populations that we compare to observations obtained by radial velocity measurements. The giant planets in our simulations migrate over large distances due to the fast type-II migration regime induced by a high disc viscosity (α = 5.4 × 10<sup>-3</sup>). Cold Jupiters (r<sub>p</sub> &gt; 1 au) originate preferably from the outer disc, due to the large-scale planetary migration, while hot Jupiters (r<sub>p</sub> &lt; 0.1 au) preferably form in the inner disc. We find that the formation of gas giants via pebble accretion is in agreement with the metallicity correlation, meaning that more gas giants are formed at larger metallicity. However, our synthetic population of isolated stars host a significant amount of giant planets even at low metallicity, in contradiction to observations where giant planets are preferably found around high metallicity stars, indicating that pebble accretion is very efficient in the standard pebble accretion framework. On the other hand, discs around stars embedded in cluster environments hardly form any giant planets at low metallicity in agreement with observations, where these changes originate from the increased temperature in the outer parts of the disc, which prolongs the core accretion time-scale of the planet. We therefore conclude that the outer disc structure and the planet's formation location determines the giant planet occurrence rate and the formation efficiency of cold and hot Jupiters.</p>},
  author       = {Ndugu, N. and Bitsch, B. and Jurua, E.},
  issn         = {0035-8711},
  keyword      = {Accretion,Accretion discs,Planets and satellites: formation,Protoplanetary discs},
  language     = {eng},
  month        = {02},
  number       = {1},
  pages        = {886--897},
  publisher    = {OXFORD UNIV PRESS},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Planet population synthesis driven by pebble accretion in cluster environments},
  url          = {http://dx.doi.org/10.1093/mnras/stx2815},
  volume       = {474},
  year         = {2018},
}