%0 Generic %1 krumholz2016physics %A Krumholz, Mark R. %A Myers, Andrew T. %A Klein, Richard I. %A McKee, Christopher F. %D 2016 %K cores imf peak simulation %T What Physics Determines the Peak of the IMF? Insights from the Structure of Cores in Radiation-Magnetohydrodynamic Simulations %U http://arxiv.org/abs/1603.04557 %X As star-forming clouds collapse, the gas within them fragments to ever-smaller masses, until the cascade of fragmentation is arrested at some mass scale, making smaller objects progressively less likely to form. This scale defines the peak of the initial mass function (IMF). In this paper we analyse radiation-magnetohydrodynamics simulations of star cluster formation in typical Milky Way environments in order to determine what physical process limits fragmentation in them. We examine the regions in the vicinity of stars that form in the simulations to determine the amounts of mass that are prevented from fragmenting by thermal and magnetic pressure. We show that, on small scales, thermal pressure enhanced by stellar radiation heating is the dominant mechanism limiting the ability of the gas to further fragment. In the brown dwarf mass regime, $0.01$ $M_ødot$, the typical object that forms in the simulations is surrounded by gas whose mass is several times its own that is unable to escape or fragment, and instead is likely to accrete. This mechanism explains why $0.01$ $M_ødot$ objects are rare: unless an outside agent intervenes (e.g., a shock strips away the gas around them), they will grow by accreting the warmed gas around them. In contrast, by the time stars grow to masses of $0.2$ $M_ødot$, the mass of heated gas is only tens of percent of the central star mass, too small to alter its final mass by a large factor. This naturally explains why the IMF peak is at $0.2-0.3$ $M_ødot$.

@misc{krumholz2016physics, abstract = {As star-forming clouds collapse, the gas within them fragments to ever-smaller masses, until the cascade of fragmentation is arrested at some mass scale, making smaller objects progressively less likely to form. This scale defines the peak of the initial mass function (IMF). In this paper we analyse radiation-magnetohydrodynamics simulations of star cluster formation in typical Milky Way environments in order to determine what physical process limits fragmentation in them. We examine the regions in the vicinity of stars that form in the simulations to determine the amounts of mass that are prevented from fragmenting by thermal and magnetic pressure. We show that, on small scales, thermal pressure enhanced by stellar radiation heating is the dominant mechanism limiting the ability of the gas to further fragment. In the brown dwarf mass regime, $\sim 0.01$ $M_\odot$, the typical object that forms in the simulations is surrounded by gas whose mass is several times its own that is unable to escape or fragment, and instead is likely to accrete. This mechanism explains why $\sim 0.01$ $M_\odot$ objects are rare: unless an outside agent intervenes (e.g., a shock strips away the gas around them), they will grow by accreting the warmed gas around them. In contrast, by the time stars grow to masses of $\sim 0.2$ $M_\odot$, the mass of heated gas is only tens of percent of the central star mass, too small to alter its final mass by a large factor. This naturally explains why the IMF peak is at $\sim 0.2-0.3$ $M_\odot$.}, added-at = {2016-03-16T09:26:52.000+0100}, author = {Krumholz, Mark R. and Myers, Andrew T. and Klein, Richard I. and McKee, Christopher F.}, biburl = {https://www.bibsonomy.org/bibtex/2211ae7b79f8fc28800f302260f26bce5/miki}, description = {[1603.04557] What Physics Determines the Peak of the IMF? Insights from the Structure of Cores in Radiation-Magnetohydrodynamic Simulations}, interhash = {e356b69532b8252dce170504e56e4d6a}, intrahash = {211ae7b79f8fc28800f302260f26bce5}, keywords = {cores imf peak simulation}, note = {cite arxiv:1603.04557Comment: 10 pages, 8 figures, submitted to MNRAS}, timestamp = {2016-03-16T09:26:52.000+0100}, title = {What Physics Determines the Peak of the IMF? Insights from the Structure of Cores in Radiation-Magnetohydrodynamic Simulations}, url = {http://arxiv.org/abs/1603.04557}, year = 2016 }