Revisiting the universality of (multiple) star formation in present-day star formation regions

TL;DR

This paper reevaluates the universality of star formation processes by analyzing binary star populations in various regions, emphasizing the importance of historical density and age in interpreting multiplicity data.

Contribution

It demonstrates that the standard model with dense past environments can explain observed populations, challenging previous conclusions about non-universality.

Findings

The standard model accounts for all known populations with historical density considerations.

Corona Australis likely has an initial density close to its current density.

Degeneracy between age and density affects interpretation of multiplicity data.

Abstract

Populations of multiple stars inside clustered regions are known to change through dynamical interactions. The efficiency of binary disruption is thought to be determined by stellar density. King and collaborators recently investigated the multiplicity properties in young star forming regions and in the Galactic field. They concluded that stellar density-dependent modification of a universal initial binary population (the standard or null hypothesis model) cannot explain the observations. We re-visit their results, analyzing the data within the framework of different model assumptions, namely non-universality without dynamical modification and universality with dynamics. We illustrate that the standard model does account for all known populations if regions were significantly denser in the past. Some of the effects of using present-day cluster properties as proxies for their past values are emphasized and that the degeneracy between age and density of a star forming region can not be omitted when interpreting multiplicity data. A new analysis of the Corona Australis region is performed within the standard model. It is found that this region is likely as unevolved as Taurus and an initial density of $\approx190M_{\odot}\;pc^{-3}$ is required to produce the presently observed binary population, which is close to its present-day density.