On the mass function of stars growing in a flocculent medium

Th. Maschberger (1)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

Stars form in regions of very inhomogeneous densities and may have chaotic orbital motions. This leads to a time variation of the accretion rate, which will spread the masses over some mass range. We investigate the mass distribution functions that arise from fluctuating accretion rates in non-linear accretion, ṁ ∝ m^α. The distribution functions evolve in time and develop a power-law tail attached to a lognormal body, like in numerical simulations of star formation. Small fluctuations may be modelled by a Gaussian and develop a power-law tail ∝ m^-α at the high-mass side for α > 1 and at the low-mass side for α < 1. Large fluctuations require that their distribution is strictly positive, for example, lognormal. For positive fluctuations the mass distribution function develops the power-law tail always at the high-mass hand side, independent of α larger or smaller than unity. Furthermore, we discuss Bondi-Hoyle accretion in a supersonically turbulent medium, the range of parameters for which non-linear stochastic growth could shape the stellar initial mass function, as well as the effects of a distribution of initial masses and growth times.

Keywords: stars: formation; stars: luminosity function; mass function; accretion; accretion discs; turbulence

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

Th. Maschberger. On the mass function of stars growing in a flocculent medium. Monthly Notices of the Royal Astronomical Society, 2013, 436, pp.1381-1389. ⟨10.1093/mnras/stt1656⟩. ⟨insu-03614199⟩