Structure and Rotation of Young Massive Star Clusters in a Simulated Dwarf Starburst
Abstract
We analyze the three-dimensional shapes and kinematics of the young star cluster population forming in a high-resolution GRIFFIN project simulation of a metal-poor dwarf galaxy starburst. The star clusters, which follow a power-law mass distribution, form from the cold phase interstellar medium with an initial mass function sampled with individual stars down to four solar masses at sub-parsec spatial resolution. Massive stars and their important feedback mechanisms are modeled in detail. The simulated clusters follow a surprisingly tight relation between the specific angular momentum and mass with indications of two sub-populations. Massive clusters (Mcl ≳ 3 × 104 M⊙) have the highest specific angular momenta at low ellipticities (ɛ ∼ 0.2) and show alignment between their shapes and rotation. Lower mass clusters have lower specific angular momenta with larger scatter, show a broader range of elongations, and are typically misaligned indicating that they are not shaped by rotation. The most massive clusters (M ≳ 105 M⊙) accrete gas and protoclusters from a ≲100 pc scale local galactic environment on a t ≲ 10 Myr timescale, inheriting the ambient angular momentum properties. Their two-dimensional kinematic maps show ordered rotation at formation, up to v ∼ 8.5 km s-1, consistent with observed young massive clusters and old globular clusters, which they might evolve into. The massive clusters have angular momentum parameters λR ≲ 0.5 and show Gauss-Hermite coefficients h3 that are anti-correlated with the velocity, indicating asymmetric line-of-sight velocity distributions as a signature of a dissipative formation process.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2020
- DOI:
- 10.3847/1538-4357/abc001
- arXiv:
- arXiv:2008.04320
- Bibcode:
- 2020ApJ...904...71L
- Keywords:
-
- Young star clusters;
- Computational astronomy;
- Stellar kinematics;
- Star formation;
- 1833;
- 293;
- 1608;
- 1569;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 21 pages, accepted for publication in ApJ