IMF in clusters: what can we say about its universality? / 本系 李悅寧 教授

The initial mass function (IMF) is suggested by observations to be universal in spite of the wide variety of star-forming environments. Several major physical mechanisms, such as thermal energy, turbulence, gravity, magnetic field, and radiation, are governing the formation of the stars, or even before that, the formation of the prestellar cores. I will discuss some possible influences of initial conditions on the mass spectrum of stars forming inside clusters. The observations suggest a high-mass end slope of -1.3 for the IMF, while this does not seem to have been readily reproduced by any of the present day simulations. A series of numerical experiments was performed with a wide range of initial density, turbulent energy level, and magnetic field strength. We compare the stellar mass spectrum outcome to the prediction adapted from the gravo-turbulent fragmentation model. The IMF from simulations is well reproduced with a powerlaw density PDF, that is often observed in collapsing clumps. Nonetheless, a shallower slope is suggested. This might give some hint of the different IMF slope observed in extreme environments.