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The Necessity of Feedback Physics in Setting the Peak of the Initial Mass Function

Guszejnov, Dávid and Krumholz, Mark R. and Hopkins, Philip F. (2016) The Necessity of Feedback Physics in Setting the Peak of the Initial Mass Function. Monthly Notices of the Royal Astronomical Society, 458 (1). pp. 673-680. ISSN 0035-8711.

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A popular theory of star formation is gravito-turbulent fragmentation, in which self-gravitating structures are created by turbulence-driven density fluctuations. Simple theories of isothermal fragmentation successfully reproduce the core mass function (CMF) which has a very similar shape to the initial mass function (IMF) of stars. However, numerical simulations of isothermal turbulent fragmentation thus far have not succeeded in identifying a fragment mass scale that is independent of the simulation resolution. Moreover, the fluid equations for magnetized, self-gravitating, isothermal turbulence are scale-free, and do not predict any characteristic mass. In this paper we show that, although an isothermal self-gravitating flow does produce a CMF with a mass scale imposed by the initial conditions, this scale changes as the parent cloud evolves. In addition, the cores that form undergo further fragmentation and after sufficient time forget about their initial conditions, yielding a scale-free pure power-law distribution dN/dM ∝ M^(−2) for the stellar IMF. We show that this problem can be alleviated by introducing additional physics that provides a termination scale for the cascade. Our candidate for such physics is a simple model for stellar radiation feedback. Radiative heating, powered by accretion on to forming stars, arrests the fragmentation cascade and imposes a characteristic mass scale that is nearly independent of the time-evolution or initial conditions in the star-forming cloud, and that agrees well with the peak of the observed IMF. In contrast, models that introduce a stiff equation of state for denser clouds but that do not explicitly include the effects of feedback do not yield an invariant IMF.

Item Type:Article
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URLURL TypeDescription Paper
Guszejnov, Dávid0000-0001-5541-3150
Krumholz, Mark R.0000-0003-3893-854X
Hopkins, Philip F.0000-0003-3729-1684
Additional Information:© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 February 8. Received 2016 January 20; in original form 2015 October 16. Published: 10 February 2016. Support for PFH and DG was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1411920 and CAREER grant #1455342. MRK is supported by NSF grants AST-0955300, AST-1405962, and NASA ATP grant NNX15AT06G. Numerical calculations were run on the Caltech computer cluster ‘Zwicky’ (NSF MRI award #PHY-0960291) and allocation TG-AST130039 granted by the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the NSF.
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:stars: formation, turbulence, galaxies: evolution, galaxies: star formation, cosmology: theory
Issue or Number:1
Record Number:CaltechAUTHORS:20160301-111609246
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Official Citation:Dávid Guszejnov, Mark R. Krumholz, Philip F. Hopkins; The necessity of feedback physics in setting the peak of the initial mass function. Mon Not R Astron Soc 2016; 458 (1): 673-680. doi: 10.1093/mnras/stw315
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64906
Deposited By: Ruth Sustaita
Deposited On:01 Mar 2016 21:31
Last Modified:09 Mar 2020 13:18

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