Disc Instability is Dead, Long Live Disc Instability

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• Duncan Forgan (St Andrews)
• Wednesday 04 May 2016, 15:30-16:15
• Martin Ryle Seminar Room, Kavli Institute.

If you have a question about this talk, please contact Dr B.-O. Demory.

Note unusual time

Disc Instability theory proposes that self-gravitating discs fragment into bound objects with masses around the giant planet/brown dwarf boundary, which is attractive for explaining planetary systems with large bodies at large semimajor axis. In its most recent incarnation, Tidal Downsizing, the disc fragments may obtain solid cores through sedimentation, migrate inwards and be tidally stripped, forming objects with a range of masses and properties.

I will present several investigations of disc fragmentation and tidal downsizing, which include high resolution radiation hydrodynamic simulations and state-of-the-art semi-analytic population synthesis models. The combined evidence is clear that disc fragments have a high mortality rate. The survivors (bound and free floating) are well within the means of current direct imaging surveys, as we demonstrate through synthetic observations, placing strong constraints on how frequently discs fragment.

However, even if fragments don’t survive, the fragmentation process irrevocably alters the disc chemistry. I will show preliminary work demonstrating that while disc instability might not be the principal formation mechanism for giant planets and brown dwarfs, it sets the initial dynamical and compositional conditions for planet formation by core accretion.

This talk is part of the Exoplanet Seminars series.

This talk is included in these lists:

• Cambridge Astronomy Talks
• Combined External Astrophysics Talks DAMTP
• Cosmology, Astrophysics and General Relativity
• Exoplanet Seminars
• Institute of Astronomy Talk Lists
• LCLU Departmental Talks
• Martin Ryle Seminar Room, Kavli Institute

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