event
Wednesday 30 Nov 2011: Dr Benoit Commercon - Study of prestellar dense core collapse and fragmentation using radiation-magneto-hydrodynamics.
Dr Benoit Commercon - Max Planck Institute fuer Astronomie
Physics, 4th floor 14:00-14:45
It is established that stars form within molecular clouds via gravitational collapse. I will present radiation-magneto-hydrodynamics calculations of low-mass and massive dense core collapse, focusing on the first collapse and the first hydrostatic core (first Larson core) formation. The influence of magnetic field and initial mass on the fragmentation properties will be investigated. In the first part, I will briefly present the numerical method I use. In the second part reporting low-mass dense core collapse calculations results, synthetic observations of spectral energy distributions will be derived, as well as classical observational quantities such as the bolometric temperature and luminosity. I will show how the dust continuum can help to target first hydrostatic cores and to state about the nature of VeLLOs. Last, I will present synthetic ALMA observation predictions of first hydrostatic cores which may give an answer, if not definitive, to the fragmentation issue at the early Class 0 stage.
In the third part, I will report the recent results of radiation-magneto-hydrodynamics calculations in the context of high mass star formation, using for the first time a self-consistent model for photon emission (i.e. via thermal emission and in radiative shocks) and with the high resolution necessary to resolve properly magnetic braking effects and radiative shocks on scales <100 AU (Commercon, Hennebelle & Henning ApJL 2011). In this study, we investigate the combined effects of magnetic field, turbulence, and radiative transfer on the early phases of the collapse and the fragmentation of massive dense cores (M=100 Msun). We identify a new mechanism that inhibits initial fragmentation of massive dense cores, where magnetic field and radiative transfer interplay. We show that this interplay becomes stronger as the magnetic field strength increases. We speculate that highly magnetized massive dense cores are good candidates for isolated massive star formation, while moderately magnetized massive dense cores are more appropriate to form OB associations or small star clusters.
