Binary star formation from ring fragmentation

Abstract

We present a simple model of binary star formation based on the assumption that rotating prestellar cores collapse to form rings and these rings then fragment into protostars. We assume that each ring spawns a small number (N <= 6) of protostars, and that the condensation of the protostars is sufficiently rapid that they can subsequently be treated as point masses. We simulate the dynamical evolution of a ring of N stars and record the properties of the single stars, binaries and higher multiples that form as a result of the dissolution of the ring. The masses of the individual stars in a ring are drawn from a log-normal distribution with dispersion σ. This part of the model is perfomed for many different realizations of the ring, to obtain good statistics. The second part of the model is to convolve the results of these dimensionless simulations, first with the distribution of core masses, which yields the distributions of multiplicity,mass ratio and eccentricity, as a function of primary mass; and second with the distribution of core angular momenta, which yields the distributions of semi-major axis and period, again as a function of primary mass. Using the observed distribution of core masses, and the observed distribution of core angular momenta, our model is able to reproduce the observed IMF, the observed high multiplicity frequency of pre-Main Sequence stars, the observed distribution of separations, and -- for long-period systems -- the observed distributions of eccentricity and mass-ratio, provided we invoke N = 4 or 5 and $\sigma =0.6$. We presume that the reduced multiplicity frequency in the field, compared with young clusters, is the result of dynamical interactions between stars formed in different cores but the same cluster, following ring dissolution.

Accepted by A&A, 14 pages, 8 figures

References in corpus (23)

• On the variation of the Initial Mass Function
• The Formation of a Bound Star Cluster: From the Orion Nebula Cluster to the Pleiades
• Inverse Dynamical Population Synthesis and Star Formation
• Star formation in clusters: a survey of compact mm-wave sources in the Serpens core
• The Dynamical Properties of Stellar Systems in the Galactic Disc
• Predicting the Properties of Binary Stellar Systems: The Evolution of Accreting Protobinary Systems
• New Brown Dwarfs and an Updated Initial Mass Function in Taurus
• New Low-Mass Members of the Taurus Star-Forming Region
• A SCUBA survey of the NGC 2068/2071 protoclusters
• The formation of close binary systems
• A High Angular Resolution Multiplicity Survey of the Open Clusters alpha Persei and Praesepe
• Turbulent Molecular Cloud Cores: Rotational Properties
• The mass ratio distribution of B-type visual binaries in the Sco OB2 association
• Membership and Multiplicity among Very Low-Mass Stars and Brown Dwarfs in the Pleiades Cluster
• Simulating star formation in molecular cores II. The effects of different levels of turbulence
• Multiple protostellar systems. I. A deep near infrared survey of Taurus and Ophiuchus protostellar objects
• On the origin of brown dwarfs and free-floating planetary mass objects
• On the origin of the distribution of binary-star periods
• Accretion and Dynamical Interactions in Small-N Star-Forming Clusters: I. N=5 case
• The dynamical evolution of Taurus--Auriga-type aggregates
• On the universal outcome of star-formation: Is there a link between stars and brown-dwarfs?
• Mass ratios of the components in T Tauri binary systems and implications for multiple star formation
• Protostellar collapse induced by compression. II: rotation and fragmentation

Cited by in corpus (35)

• Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation
• Stellar, Brown Dwarf, and Multiple Star Properties from Hydrodynamical Simulations of Star Cluster Formation
• The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation
• The VAST Survey - III. The multiplicity of A-type stars within 75 pc
• Mapping the Shores of the Brown Dwarf Desert I.: Upper Scorpius
• Radiation-Hydrodynamic Simulations of the Formation of Orion-Like Star Clusters II. The Initial Mass Function from Winds, Turbulence, and Radiation
• Towards a more realistic sink particle algorithm for the RAMSES code
• On the evolution of a star cluster and its multiple stellar systems following gas dispersal
• Star Cluster Formation in Turbulent, Magnetized Dense Clumps with Radiative and Outflow Feedback
• The statistical properties of stars and their dependence on metallicity
• The statistical properties of stars and their dependence on metallicity: the effects of opacity
• The Role of Mass and Environment in Multiple Star Formation: A 2MASS Survey of Wide Multiplicity in Three Young Associations
• Exploring the consequences of pairing algorithms for binary stars
• The importance of magnetic fields for the initial mass function of the first stars
• Multiplicity and Optical Excess Across the Substellar Boundary in Taurus
• The relationship between the prestellar core mass function and the stellar initial mass function
• On the frequency of close binary systems among very low-mass stars and brown dwarfs
• Search for associations containing young stars (SACY). V. Is multiplicity universal? Tight multiple systems
• The Formation of Stellar Clusters in Magnetized, Filamentary Infrared Dark Clouds
• Brown dwarf formation by binary disruption
• The effect of radiative feedback on disc fragmentation
• Star formation in molecular cores III. The effect of the turbulent power spectrum
• Protostellar Feedback in Turbulent Fragmentation: Consequences for Stellar Clustering and Multiplicity
• Simulating star formation in molecular cloud cores IV. The role of turbulence and thermodynamics
• Mapping the core mass function onto the stellar IMF: multiplicity matters
• Are the majority of Sun-like stars single?
• The dynamical evolution of low-mass hydrogen-burning stars, brown dwarfs and planetary-mass objects formed through disc fragmentation
• A Numerical Study of Brown Dwarf Formation via Encounters of Protostellar Disks
• The role of the H${}_2$ adiabatic index in the formation of the first stars
• The statistical properties of stars at redshift, z=5, compared with the present epoch
• The formation of brown dwarfs
• The distribution of ejected brown dwarfs in clusters
• Close binary systems among very low mass stars and brown dwarfs
• On the survivability of a population of gas giant planets on wide orbits
• Fundamental parameters of the eclipsing binary DD CMa and evidence for mass exchange