http://arxiv.org/abs/1702.04431
One of the key observations regarding the stellar initial mass function (IMF) is its near-universality in the Milky Way (MW), which provides a powerful way to test different star formation models that predict the IMF. However, those models are almost universally “cloud-scale” or smaller — they take as input or simulate single molecular clouds (GMCs), clumps, or cores, and predict the resulting IMF as a function of the cloud properties. Without a model for the progenitor properties of all clouds which formed the stars at different locations in the MW (including ancient stellar populations formed in high-redshift, likely gas-rich dwarf progenitor galaxies that looked little like the Galaxy today), the predictions cannot be explored. We therefore utilize a high-resolution fully-cosmological simulation (from the Feedback In Realistic Environments project), which forms a MW-like galaxy with reasonable mass, morphology, abundances, and star formation history, and explicitly resolves massive GMCs; we combine this with several cloud-scale IMF models applied independently to {\em every star-forming resolution element} in the simulation to synthesize the predicted IMF variations in the present-day galaxy. We specifically explore broad classes of models where the IMF depends on the Jeans mass, the sonic or “turbulent Bonner-Ebert” mass, fragmentation with some polytropic equation-of-state, or where it is self-regulated by proto-stellar feedback. We show that all of these models, except the feedback-regulated models, predict far more variation ($\sim 0.6-1$ dex $1\,\sigma$ scatter in the IMF turnover mass) than is observed in the MW. This strongly constraints the parameters that can drive IMF variation in nearby galaxies, as well.
D. Guszejnov, P. Hopkins and X. Ma
Thu, 16 Feb 17
34/45
Comments: 5 pages, 4 figures Submitted to MNRAS
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