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

Wright, Nick

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.

Citation

Wright, N., & Parker, R. J. (2018). Evolution of spatio-kinematic structures in star-forming regions: are Friends of Friends worth knowing?. Monthly Notices of the Royal Astronomical Society, 481(2), 1679-1689. https://doi.org/10.1093/mnras/sty2372

• Journal Article Type: Article
• Acceptance Date: Aug 29, 2018
• Publication Date: Sep 3, 2018
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Publisher: Oxford University Press
• Volume: 481
• Issue: 2
• Pages: 1679-1689
• DOI: https://doi.org/10.1093/mnras/sty2372
• Keywords: stars: formation – kinematics and dynamics – open clusters and associations: general – methods: numerical
• Publisher URL: http://dx.doi.org/10.1093/mnras/sty2372