On the coupled origin of the stellar IMF and multiplicity

Abstract

In the solar neighborhood, the Initial Mass Function (IMF) follows is canonically described by the Salpeter power-law slope for the high-mass range. The stellar IMF may directly result from a Core Mass Function (CMF) through accretion, gravitational collapse, and fragmentation. This inheritance implies that the mass of the gaseous fragments may be connected to the properties of clustered and multiple stellar systems. We aim to (i) quantify the influence of hierarchical fragmentation of cores on the resulting IMF, and (ii) determine the consequences of this fragmentation on the multiplicity of the stellar systems. We employed a scale-free, hierarchical fragmentation model to investigate the fragmentation of top-heavy CMF. Hierarchical fragmentation of gas clumps shifts the CMF towards lower mass range and can modify its shape. Starting from the top-heavy power-law CMF observed in W43-MM2&MM3 star forming region, we show that at least four levels of hierarchical fragmentation are required to generate the turn-over peak of the cIMF. Within a radius of 0.2-2.5 kAU, massive stars (M > 10 Msun) have on average 0.9 companions, five times fewer than low-mass stars (M < 0.1 Msun); the latter are less dynamically stable and should disperse. We show that a universal IMF can emerge from mass-dependent fragmentation processes provided that more massive cores produce less fragments compared to lower mass cores and transfer their mass less efficiently to their fragments. Hierarchical fragmentation alone cannot reconcile a universal IMF with observed stellar multiplicity. We propose that fragmentation is not scale-free but operates in two distinct regimes: a mass-dependent phase establishing the Salpeter slope and a mass-independent phase setting the turn-over. Our framework provides a way to compare core subfragmentation in various star-forming regions and numerical simulations.

References in corpus (17)

• Analytical theory for the initial mass function: CO clumps and prestellar cores
• On the Density Distribution in Star-forming Interstellar Clouds
• A SCUBA survey of Orion, the low-mass end of the core mass function
• Comparing Star Formation on Large Scales in the c2d Legacy Clouds: Bolocam 1.1 mm Dust Continuum Surveys of Serpens, Perseus, and Ophiuchus
• The Fragmentation of Magnetized, Massive Star-Forming Cores with Radiative Feedback
• Properties of the dense core population in Orion B as seen by the Herschel Gould Belt survey
• The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. IV. A Super-Salpeter IMF in the center of NGC 1407 from Non-Parametric Models
• The W43-MM1 mini-starburst ridge, a test for star formation efficiency models
• Characterizing the Brown Dwarf Formation Channels from the Initial Mass Function and Binary-star Dynamics
• Bondi-Hoyle-Littleton accretion and the upper mass stellar IMF
• ALMA-IMF. V. Prestellar and protostellar core populations in the W43 cloud complex
• The Origin of the Stellar Mass Distribution and Multiplicity
• ALMA-IMF XV: The core mass function in the high-mass star-formation regime
• Strong dependence of the physical properties of cores on spatial resolution in observations and simulations
• The effect of the environment-dependent stellar initial mass function on the photometric properties of star-forming galaxies
• The Impact of Early Massive Galaxy Formation on the Cosmic Microwave Background
• A stochastic and analytical model of hierarchical fragmentation: The fragmentation of gas structures into young stellar objects in the interstellar medium