Abstract
Recently, the gravitational instability (GI) model of giant planet and
brown dwarf formation has been revisited and recast into what is often
referred to as the "tidal downsizing" hypothesis. The fragmentation of
self-gravitating protostellar discs into gravitationally bound embryos -
with masses of a few to tens of Jupiter masses, at semi major axes above
30 - 40 AU - is followed by a combination of grain sedimentation inside
the embryo, radial migration towards the central star and tidal
disruption of the embryo's upper layers. The properties of the resultant
object depends sensitively on the timescales upon which each process
occurs. Therefore, GI followed by tidal downsizing can theoretically
produce objects spanning a large mass range, from terrestrial planets to
giant planets and brown dwarfs. Whether such objects can be formed in
practice, and what proportions of the observed population they would
represent, requires a more involved statistical analysis.
We present a simple population synthesis model of star and planet
formation via GI and tidal downsizing. We couple a semi-analytic model
of protostellar disc evolution to analytic calculations of
fragmentation, initial embryo mass, grain growth and sedimentation,
embryo migration and tidal disruption. While there are key pieces of
physics yet to be incorporated, it represents a first step towards a
mature statistical model of GI and tidal downsizing as a mode of star
and planet formation.
We show results from four runs of the population synthesis model,
varying the opacity law and the strength of migration, as well as
investigating the effect of disc truncation during the fragmentation
process.
Original language | English |
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Publication status | Published - 1 Jul 2013 |
Event | Protostars and Planets VI - Heidelberg, Germany Duration: 15 Jul 2013 → 20 Jul 2013 |
Conference
Conference | Protostars and Planets VI |
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Country/Territory | Germany |
City | Heidelberg |
Period | 15/07/13 → 20/07/13 |