Can giant planets form by gravitational fragmentation of discs - AstrophysicsReport as inadecuate

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Abstract: Gravitational fragmentation has been proposed as a mechanism for theformation of giant planets in close orbits around solar-type stars. However, itis debatable whether this mechanism can function in the inner regions R<40 AUof real discs. We use a newly developed method for treating the energy equationand the equation of state, which accounts for radiative transfer effects in SPHsimulations of circumstellar discs. The different chemical and internal statesof hydrogen and the properties of dust at different densities and temperaturesice coated dust grains at low temperatures, ice melting, dust sublimation areall taken into account by the new method.We present radiative hydrodynamicsimulations of the inner regions of massive circumstellar discs and examine twocases: i a disc irradiated by a cool background radiation fieldT bgr=10Kand ii a disc heated by radiation from its central starT bgr~1-R. In neither case does the disc fragment: in the former because itcannot cool fast enough and in the latter because it is not gravitationallyunstable. Our results a corroborate previous numerical results usingdifferent treatments for the hydrodynamics and the radiative transfer, and bconfirm our own earlier analytic predictions. We conclude that discfragmentation is unlikely to be able to produce giant planets around solar-typestars at radii <40 AU.

Author: Dimitris Stamatellos, Anthony P. Whitworth School of Physics and Astronomy, Cardiff University, UK


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