Binary Disruption and Ejected Stars from Hierarchical Star Cluster Assembly

arXiv (Cornell University)

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 which include a prescription for binaries based on observations. We also find a preferred direction of motion for stars that become unbound during the merger. Sub-cluster 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 semi-major axes are disrupted in simulations of sub-cluster 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 sub-cluster 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

2. Jeremy Karam

   McMaster University

   Affiliation as printed

   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

4. Simon Portegies Zwart Aachen Sterrewacht Leiden

   Leiden University · University of Applied Sciences Leiden

   Affiliation as printed

   Sterrewacht Leiden , Leiden University , Niels Bohrweg 2 , 2333 Leiden , The Netherlands

5. M. Wilhelm Aachen Sterrewacht Leiden

   Leiden University · University of Applied Sciences Leiden

   Affiliation as printed

   Sterrewacht Leiden , Leiden University , Niels Bohrweg 2 , 2333 Leiden , The Netherlands