Testing the turbulent origin of the stellar initial mass function
Abstract
Supersonic turbulence in the interstellar medium (ISM) is closely linked to the formation of stars; hence, many theories connect the stellar initial mass function (IMF) with the turbulent properties of molecular clouds. Here, we test three turbulencebased IMF models (by Padoan and Nordlund, Hennebelle and Chabrier, and Hopkins) that predict the relation between the highmass slope (Γ) of the IMF, dN/d log M ∝ M^{Γ}, and the exponent n of the velocity power spectrum of turbulence, E_{v}(k) ∝ k^{n}, where n ≈ 2 corresponds to typical ISM turbulence. Using hydrodynamic simulations, we drive turbulence with an unusual index of n ≈ 1, measure Γ, and compare the results with n ≈ 2. We find that reducing n from 2 to 1 primarily changes the highmass region of the IMF (beyond the median mass), where we measure highmass slopes within the 95 per cent confidence interval of 1.5 < Γ < 1 for n ≈ 1 and 3.7 < Γ < 2.4 for n ≈ 2, respectively. Thus, we find that n = 1 results in a significantly flatter highmass slope of the IMF, with more massive stars formed than for n ≈ 2. We compare these simulations with the predictions of the three IMF theories. We find that while the theory by Padoan and Nordlund matches our simulations with fair accuracy, the other theories either fail to reproduce the main qualitative outcome of the simulations or require some modifications. We conclude that turbulence plays a key role in shaping the IMF, with a shallower turbulence power spectrum producing a shallower highmass IMF, and hence more massive stars.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 May 2021
 DOI:
 10.1093/mnras/stab505
 arXiv:
 arXiv:2102.08564
 Bibcode:
 2021MNRAS.503.1138N
 Keywords:

 hydrodynamics;
 turbulence;
 methods: numerical;
 stars: luminosity function;
 mass function;
 ISM: clouds;
 Astrophysics  Astrophysics of Galaxies;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 doi:10.1093/mnras/stab505