Humphries_2020_ALMA.pdf (18.45 MB)
Searching for wide-orbit gravitational instability protoplanets with ALMA in the dust continuum
journal contribution
posted on 2022-10-10, 14:08 authored by J Humphries, C Hall, TJ Haworth, S NayakshinSearches for young gas giant planets at wide separations have so far focused on techniques appropriate for compact (Jupiter-sized) planets. Here, we point out that protoplanets born through gravitational instability (GI) may remain in an initial pre-collapse phase for as long as the first 105-107 yr after formation. These objects are hundreds of times larger than Jupiter and their atmospheres are too cold (T ∼tens of K) to emit in the near-infrared or Hα via accretion shocks. However, it is possible that their dust emission can be detected with Atacama Large Millimeter/submillimeter Array (ALMA), even around Classes I and II protoplanetary discs. In this paper, we produce synthetic observations of these protoplanets. We find that making a detection in a disc at 140 pc would require a few hundred minutes of ALMA band 6 observation time. Protoplanets with masses of 3-5 MJ have the highest chance of being detected; less massive objects require unreasonably long observation times (1000 min), while more massive ones collapse into giant planets before 105 yr. We propose that high-resolution surveys of young (105-106 yr), massive and face on discs offer the best chance for observing protoplanets. Such a detection would help to place constraints on the protoplanet mass spectrum, explain the turnover in the occurrence frequency of gas giants with system metallicity and constrain the prevalence of GI as a planet formation mechanism. Consistent lack of detection would be evidence against GI as a common planet formation mechanism.
Funding
Astrophysics Research at the University of Leicester
Science and Technology Facilities Council
Find out more...Royal Society Dorothy Hodgkin Fellowship
Winton Fellow and this work has been supported by Winton Philanthropies/The David and Claudia Harding Foundation
History
Author affiliation
Department of Physics and Astronomy, University of LeicesterVersion
- AM (Accepted Manuscript)
Published in
Monthly Notices of the Royal Astronomical SocietyVolume
502Issue
1Pagination
953 - 968Publisher
Oxford University Press (OUP) for Royal Astronomical Societyissn
0035-8711eissn
1365-2966Copyright date
2021Available date
2022-10-10Publisher DOI
Notes
15 pages, 13 figures, accepted to MNRASLanguage
EnglishPublisher version
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Keywords
Science & TechnologyPhysical SciencesAstronomy & Astrophysicsaccretion, accretion discsprotoplanetary discsbrown dwarfsplanets and satellites: detectionplanets and satellites: formationplanets and satellites: gaseous planetsGIANT PLANETSCIRCUMSTELLAR DISKSKINEMATIC EVIDENCEACCRETIONGASSUBSTRUCTURESEMISSIONMASSMODELSGROWTH