Evolution of spatio-kinematic structures in star-forming regions: are Friends of Friends worth knowing?

Abstract

The Friends of Friends algorithm identifies groups of objects with similar spatial and kinematic properties, and has recently been used extensively to quantify the distributions of gas and stars in young star-forming regions. We apply the Friends of Friends algorithm to $N$-body simulations of the dynamical evolution of subvirial (collapsing) and supervirial (expanding) star-forming regions. We find that the algorithm picks out a wide range of groups (1 -- 25) for statistically identical initial conditions, and cannot distinguish between subvirial and supervirial regions in that we obtain similar mode and median values for the number of groups it identifies. We find no correlation between the number of groups identified initially and either the initial or subsequent spatial and kinematic tracers of the regions' evolution, such as the amount of spatial substructure, dynamical mass segregation, or velocity dispersion. We therefore urge caution in using the Friends of Friends algorithm to quantify the initial conditions of star formation.

12 pages, 8 figures, accepted for publication in MNRAS

References in corpus (20)

• A Spitzer Survey of Young Stellar Clusters within One Kiloparsec of the Sun: Cluster Core Extraction and Basic Structural Analysis
• Using the minimum spanning tree to trace mass segregation
• An ALMA study of the Orion Integral Filament: I. Evidence for narrow fibers in a massive cloud
• The Spatial Structure of Young Stellar Clusters. I. Subclusters
• The Kinematics of the Scorpius-Centaurus OB Association from Gaia DR1
• Gravity drives the evolution of infrared dark hubs: JVLA observations of SDC13
• IN-SYNC II: Virial Stars from Sub-Virial Cores -- The Velocity Dispersion of Embedded Pre-Main-Sequence Stars in NGC 1333
• Stability of Multiplanetary Systems in Star Clusters
• Synthetic C${}^{18}$O observations of fibrous filaments: the problems of mapping from PPV to PPP
• Testing Larson's relationships in massive clumps
• Strong effect of the cluster environment on the size of protoplanetary discs?
• Investigating the structure and fragmentation of a highly filamentary IRDC
• Dynamics versus structure: breaking the density degeneracy in star formation
• Comparisons between different techniques for measuring mass segregation
• Kinematics and Structure of Star-forming Regions: Insights from Cold Collapse Models
• The Structural Evolution of Forming and Early Stage Star Clusters
• ${\mathcal{Q}}^{+}$: Characterising the structure of young star clusters
• How do binary clusters form?
• J plots: a new method for characterizing structures in the interstellar medium
• On the Dispersal of Young Stellar Hierarchies

Cited by in corpus (5)

• Constraints on star formation in NGC2264
• S2D2: Small-scale Significant substructure DBSCAN Detection I. NESTs detection in 2D star-forming regions
• The evolution of phase space densities in star-forming regions
• Kinematics of Subclusters in Star Cluster Complexes: Imprint of their Parental Molecular Clouds
• Deviations from the universal Initial Mass Function in binary star clusters