Primordial mass segregation of star clusters with primordial binaries

Abstract

Observations of young star-forming regions suggest that star clusters are born completely mass segregated. These initial conditions are, however, gradually lost as the star cluster evolves dynamically. For star clusters with single stars only and a canonical initial mass function, it has been suggested that traces of these initial conditions vanish at a time ${\tau }_{\mathrm{v}}$ between 3 and $3.5t_{\mathrm{rh}}$ (initial half-mass relaxation times). Since a significant fraction of stars are observed in binary systems and it is widely accepted that most stars are born in binary systems, we aim to investigate what role a primordial binary population (even up to $100\%$ binaries) plays in the loss of primordial mass segregation of young star clusters. We used numerical $N$-body models similar in size to the Orion Nebula Cluster (ONC) -- a representative of young open clusters -- integrated over several relaxation times to draw conclusions on the evolution of its mass segregation. We also compared our models to the observed ONC. We found that ${\tau }_{\mathrm{v}}$ depends on the binary star fraction and the distribution of initial binary parameters that include a semi-major axis, eccentricity, and mass ratio. For instance, in the models with $50\%$ binaries, we find ${\tau }_{\mathrm{v}}=(2.7\pm 0.8)t_{\mathrm{rh}}$, while for $100\%$ binary fraction, we find a lower value ${\tau }_{\mathrm{v}}=(2.1\pm 0.6)t_{\mathrm{rh}}$. We also conclude that the initially completely mass segregated clusters, even with binaries, are more compatible with the present-day ONC than the non-segregated ones.

arXiv comment11 pages, 2 tables, 9 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (38)

• On the variation of the Initial Mass Function
• Binary interaction dominates the evolution of massive stars
• Evolution of binary stars and the effect of tides on binary populations
• A Survey of Stellar Families: Multiplicity of Solar-Type Stars
• Comprehensive analytic formulae for stellar evolution as a function of mass and metallicity
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• Mind your Ps and Qs: the Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars
• The Pulsar Kick Velocity Distribution
• Inverse Dynamical Population Synthesis and Star Formation
• The maximum stellar mass, star-cluster formation and composite stellar populations
• The distances to Galactic low-mass X-ray binaries: consequences for black hole luminosities and kicks
• The Dynamical Properties of Stellar Systems in the Galactic Disc
• Merging black holes in young star clusters
• The stellar and sub-stellar IMF of simple and composite populations
• Inverse dynamical population synthesis: Constraining the initial conditions of young stellar clusters by studying their binary populations
• Mass segregation and fractal substructure in young massive clusters: (I) the McLuster code and method calibration
• Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction
• Dynamical ejections of massive stars from young star clusters under diverse initial conditions
• Limits on the primordial stellar multiplicity
• Visual Binaries in the Orion Nebula Cluster
• Evidence for primordial mass segregation in globular clusters
• Dependency of dynamical ejections of O stars on the masses of very young star clusters
• Testing the universality of star formation - I. Multiplicity in nearby star-forming regions
• Distribution of Serpens South protostars revealed with ALMA
• Dynamical population synthesis: Constructing the stellar single and binary contents of galactic field populations
• On the initial binary population for star cluster simulations
• Characterizing the Brown Dwarf Formation Channels from the Initial Mass Function and Binary-star Dynamics
• Evidence for feedback and stellar-dynamically regulated bursty star cluster formation: the case of the Orion Nebula Cluster
• Complete ejection of OB stars from very young star clusters and the formation of multiple populations
• The Global Mass Functions of 35 Galactic globular clusters: II. Clues on the Initial Mass Function and Black Hole Retention Fraction
• Do star clusters form in a completely mass-segregated way?
• The moment of core collapse in star clusters with a mass function
• Captured older stars as the reason for apparently prolonged star formation in young star clusters
• The galactic evolution of the supernova rates
• The extinction map of the OMC-1 molecular cloud behind the Orion Nebula
• The black hole retention fraction in star clusters
• The hunt for self-similar core collapse
• Catch me if you can: is there a runaway-mass black hole in the Orion Nebula Cluster?

Cited by in corpus (6)

• Spin misalignment of black hole binaries from young star clusters: implications for the origin of gravitational waves events
• Stellar mass segregation as separating classifier between globular clusters and ultra-faint dwarf galaxies
• A deep investigation of two poorly studied open clusters Haffner 22 and Melotte 71 in Gaia era
• Tracing the Origins of Mass Segregation in M35: Evidence for Primordially Segregated Binaries
• Detailed analysis of the poorly studied northern open cluster NGC 1348 using multi-color photometry and GAIA EDR3 astrometry
• Spatial mixing of stellar populations in globular clusters via binary-single star scattering