Stochastically sampled IMF alters the stellar content of simulated dwarf galaxies

Elaad Applebaum, Alyson M. Brooks, Thomas R. Quinn, Charlotte R. Christensen

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Cosmological simulations are reaching the resolution necessary to study ultra-faint dwarf galaxies.Observations indicate that in small populations, the stellar initialmass function (IMF) is not fully populated; rather, stars are sampled in a way that can be approximated as coming from an underlying probability density function. To ensure the accuracy of cosmological simulations in the ultra-faint regime, we present an improved treatment of the IMF. We implement a self-consistent, stochastically populated IMF in cosmological hydrodynamic simulations. We test our method using high-resolution simulations of a Milky Way halo, run to z = 6, yielding a sample of nearly 100 galaxies. We also use an isolated dwarf galaxy to investigate the resulting systematic differences in galaxy properties. We find that a stochastic IMF in simulations makes feedback burstier, strengthening feedback, and quenching star formation earlier in small dwarf galaxies. For galaxies in haloes with mass ≤ 108.5 M, a stochastic IMF typically leads to lower stellar mass compared to a continuous IMF, sometimes by more than an order of magnitude. We show that existing methods of ensuring discrete supernovae incorrectly determine the mass of the star particle and its associated feedback. This leads to overcooling of surrounding gas, with at least ~10 per cent higher star formation and ~30 per cent higher cold gas content. Going forwards, to accurately model dwarf galaxies and compare to observations, it will be necessary to incorporate a stochastically populated IMF that samples the full spectrum of stellar masses.

Original languageEnglish (US)
Pages (from-to)8-21
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume492
Issue number1
DOIs
StatePublished - Feb 1 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Galaxies: dwarf
  • Galaxies: formation
  • Galaxies: star formation
  • Methods: numerical
  • Supernovae: general

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