Binary Disruption and Ejected Stars from Hierarchical Star Cluster Assembly

The Astrophysical Journal, vol. 975, pp. 207

Abstract

Abstract We simulate mergers between star clusters embedded within their natal giant molecular cloud. We extract initial conditions from cloud-scale simulations of cluster formation and introduce different prescriptions for primordial binaries. We find that simulations that do not include primordial binaries result in a larger fraction of unbound stars than simulations that include a prescription for binaries based on observations. We also find a preferred direction of motion for stars that become unbound during the merger. Subcluster mergers within realistic gas environments promote binary disruption, while mergers between idealized, gas-rich spherical clusters do not produce the same disruption. Binary systems with smaller semimajor axes are disrupted in simulations of subcluster mergers within their natal environment compared to simulations that do not include the realistic gas environment. We conclude that binary disruption and the production of an anisotropic distribution of unbound stars are the natural consequences of subcluster mergers during star cluster assembly.

Authors 5

1. Claude Cournoyer-Cloutier

   McMaster University

   Affiliation as printed

   Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada; cournoyc@mcmaster.ca

   Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada

2. Jeremy Karam

   McMaster University

   Affiliation as printed

   Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada; cournoyc@mcmaster.ca

   Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada

3. Alison Sills

   McMaster University

   Affiliation as printed

   Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada; cournoyc@mcmaster.ca

   Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4M1, Canada

4. Simon Portegies Zwart Aachen Sterrewacht Leiden

   Leiden University · Leiden Observatory

   Affiliation as printed

   Sterrewacht Leiden, Leiden University, Einsteinweg 55, 2333CC Leiden, The Netherlands

5. Maite J. C. Wilhelm Aachen Sterrewacht Leiden

   Leiden University · Leiden Observatory

   Affiliation as printed

   Sterrewacht Leiden, Leiden University, Einsteinweg 55, 2333CC Leiden, The Netherlands