The Origin of Massive Stars: The Inertial-inflow Model

Abstract

We address the problem of the origin of massive stars, namely the origin, path and timescale of the mass flows that create them. Based on extensive numerical simulations, we propose a scenario where massive stars are assembled by large-scale, converging, inertial flows that naturally occur in supersonic turbulence. We refer to this scenario of massive-star formation as the Inertial-Inflow Model. This model stems directly from the idea that the mass distribution of stars is primarily the result of turbulent fragmentation. Under this hypothesis, the statistical properties of the turbulence determine the formation timescale and mass of prestellar cores, posing definite constraints on the formation mechanism of massive stars. We quantify such constraints by the analysis of a simulation of supernova-driven turbulence in a 250-pc region of the interstellar medium, describing the formation of hundreds of massive stars over a time of approximately 30 Myr. Due to the large size of our statistical sample, we can say with full confidence that massive stars in general do not form from the collapse of massive cores, nor from competitive accretion, as both models are incompatible with the numerical results. We also compute synthetic continuum observables in Herschel and ALMA bands. We find that, depending on the distance of the observed regions, estimates of core mass based on commonlyused methods may exceed the actual core masses by up to two orders of magnitude, and that there is essentially no correlation between estimated and real core masses.

Collapse of turbulent massive cores with ambipolar diffusion and hybrid radiative transfer

“…This condition is strengthened by the nonideal MHD frame, which leads to smaller disks than in the hydrodynamical case (see, e.g., Hennebelle et al 2016a;Masson et al 2016). As claimed by various models, such as the global hierarchical collapse model (Vázquez-Semadeni et al 2009) and the inertialinflow model (Padoan et al 2020), and supported by various observations (Schneider et al 2010), the large-scale dynamics likely plays a major role in the formation of massive stars, and the isolation we have assumed may be an oversimplification, in particular for the turbulence as it is modeled in this paper. We leave this to further work.…”

“…This model is hampered by the rareness of high-mass prestellar cores (Motte et al 2018), although candidates exist (e.g., Nony et al 2018), and formation in isolation may not be the most common procedure. Global models such as the global hierarchical collapse model (GHC hereafter, Vázquez-Semadeni et al 2016) and the inertial-inflow model (II hereafter, Padoan et al 2020) challenge this corefed accretion scenario and instead prefer large-scale dynamics, either due to collapse (GHC) or to the inertial motions following supernova feedback (II). They suggest the inclusion (and possible requirement) of turbulence.…”

ALMA–IRDC: dense gas mass distribution from cloud to core scales

“…Although, other theories have emerged more recently (e.g. Vázquez-Semadeni et al 2019;Padoan et al 2020). This paper provides the first in a suite of observational tests that aim at differentiating between these various prescriptions for high-mass star formation.…”

Fragmentation and kinematics in high-mass star formation

“…Alternatively, they may fragment into more massive cores with potentially less lowmass cores early on (e.g., Tan et al 2014;Zhang et al 2015;Csengeri et al 2017;Beuther et al 2018)? We ask how important filamentary accretion processes are (e.g., Schneider et al 2010;Peretto et al 2014;André et al 2014;Chira et al 2018;Hennebelle 2018;Padoan et al 2020) and what the relative importance is of cloud-scale gravo-turbulent or thermal fragmentation versus fragmentation of the gravitationally unstable accretion flows for the star formation process (e.g., Peters et al 2010)? Furthermore, it has been argued that high-mass star formation starts and proceeds in turbulent gas clumps (e.g., McKee & Tan 2003).…”