3 years ago

What FIREs Up Star Formation: the Emergence of the Kennicutt-Schmidt Law from Feedback.

Philip Hopkins, Norman Murray, T.K. Chan, Robert Feldmann, Matthew E. Orr, Dušan Kereš, Claude-André Faucher-Giguère, Eliot Quataert, Christopher C. Hayward

We present an analysis of the global and spatially-resolved Kennicutt-Schmidt star formation relation in the FIRE (Feedback In Realistic Environments) suite of cosmological simulations, including halos with $z = 0$ masses ranging from $10^{10}$ -- $10^{13}$ M$_{\odot}$. We show that the Kennicutt-Schmidt (KS) relation emerges and is robustly maintained due to the effects of feedback on local scales regulating star-forming gas, independent of the particular small-scale star formation prescriptions employed. This is true for the KS relation measured using neutral (atomic + molecular) and only `cold \& dense' (as a proxy for molecular) gas. We demonstrate that the time-averaged KS relation is relatively independent of redshift and spatial averaging scale, and that the star formation rate surface density is weakly dependent on metallicity and inversely dependent on orbital dynamical time. Finally, we show that on scales larger than individual giant molecular clouds, the primary condition that determines whether star formation occurs is whether a patch of the galactic disk is thermally Toomre-unstable (not whether it is self-shielding): once a patch can no longer be thermally stabilized against fragmentation, it collapses, becomes self-shielding, cools, and forms stars, regardless of epoch or environment.

Publisher URL: http://arxiv.org/abs/1701.01788

DOI: arXiv:1701.01788v2

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