A Dual Power Law Distribution for the Stellar Initial Mass Function

Abstract

We introduce a new dual power law (DPL) probability distribution function for the mass distribution of stellar and substellar objects at birth, otherwise known as the initial mass function (IMF). The model contains both deterministic and stochastic elements, and provides a unified framework within which to view the formation of brown dwarfs and stars resulting from an accretion process that starts from extremely low mass seeds. It does not depend upon a top down scenario of collapsing (Jeans) masses or an initial lognormal or otherwise IMF-like distribution of seed masses. Like the modified lognormal power law (MLP) distribution, the DPL distribution has a power law at the high mass end, as a result of exponential growth of mass coupled with equally likely stopping of accretion at any time interval. Unlike the MLP, a power law decay also appears at the low mass end of the IMF. This feature is closely connected to the accretion stopping probability rising from an initially low value up to a high value. This might be associated with physical effects of ejections sometimes (i.e., rarely) stopping accretion at early times followed by outflow driven accretion stopping at later times, with the transition happening at a critical time (therefore mass). Comparing the DPL to empirical data, the critical mass is close to the substellar mass limit, suggesting that the onset of nuclear fusion plays an important role in the subsequent accretion history of a young stellar object.

6 pages, 2 figures, to appear in MNRAS

References in corpus (28)

• Galactic Stellar and Substellar Initial Mass Function
• On the variation of the Initial Mass Function
• The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems
• The Stellar IMF from Turbulent Fragmentation
• Analytical theory for the initial mass function: CO clumps and prestellar cores
• Theory of Low-Mass Stars and Substellar Objects
• The Burst Mode of Protostellar Accretion
• The initial mass function : from Salpeter 1955 to 2005
• The burst mode of accretion and disk fragmentation in the early embedded stages of star formation
• A Theory of the IMF for Star Formation in Molecular Clouds
• The "Mysterious" Origin of Brown Dwarfs
• Variable protostellar accretion with episodic bursts
• Analytical theory for the initial mass function: II. Properties of the flow
• The Initial Mass Function of the Orion Nebula Cluster across the H-burning limit
• Evidence for a Turnover in the IMF of Low Mass Stars and Sub-stellar Objects: Analysis from an Ensemble of Young Clusters
• A Hybrid Scenario for the Formation of Brown Dwarfs and Very Low Mass Stars
• Interferometric Identification of a Pre-Brown Dwarf
• On the Power-Law Tail in the Mass Function of Protostellar Condensations and Stars
• Stellar mass spectrum within massive collapsing clumps II. Thermodynamics and tidal forces of the first Larson core
• Characterizing the Brown Dwarf Formation Channels from the Initial Mass Function and Binary-star Dynamics
• Testing the universality of the IMF with Bayesian statistics: young clusters
• The low-mass content of the massive young star cluster RCW 38
• Stellar mass spectrum within massive collapsing clumps I. Influence of the initial conditions
• The bimodal initial mass function in the Orion Nebula Cloud
• Analytic Models of Brown Dwarfs and The Substellar Mass Limit
• The MLP Distribution: A Modified Lognormal Power-Law Model for the Stellar Initial Mass Function
• Ejection of gaseous clumps from gravitationally unstable protostellar disks
• Forming isolated brown dwarfs by turbulent fragmentation

Cited by in corpus (6)

• Preliminary Trigonometric Parallaxes of 184 Late-T and Y Dwarfs and an Analysis of the Field Substellar Mass Function into the "Planetary" Mass Regime
• The Origin of the Stellar Mass Distribution and Multiplicity
• System IMF of the 25 Ori Group from Planetary-Mass Objects to Intermediate/High-Mass Stars
• A Multiple Power Law Distribution for Initial Mass Functions
• A semi-analytic model for the temporal evolution of the episodic disc-to-star accretion rate during star formation
• Using the Modified Lognormal Power Law Distribution to Model the Mass Function of NGC 1711