We perform a suite of hydrodynamical simulations to investigate the effects of initial density profiles on the evolution of star clusters in giant molecular clouds using the moving-mesh code Arepo. We find that the uniform profile follows a "hierarchical" cluster formation mode, while the steep power-law profiles show an "accretion" dominated mode. These two cluster formation modes lead to different proprieties of the most massive clusters in giant molecular clouds.

Figure: "hierarchical" mode of cluster formation.

We develop a continuous star cluster formation model in the cosmological hydrodynamic code ART to simulate the effects of clustered star formation during the cosmic morning (z = 3 - 10) on the observational properties of the earliest galaxies by the Hubble and James Webb Space Telescopes. This is a work in progress.

Figure: sketch of a star-froming cloud in simulations.

The advent of the Gaia mission has enabled detailed chemical and kinematic studies of the Galactic globular clusters and revolutionized our understanding of the connections between globular cluster properties and galaxy assembly. By assigning globular clusters to particles in the IllustrisTNG simulation based on age and location, we develop a new globular cluster formation model with chemical, spatial, and kinematic information. The model successfully reproduces the radial distribution and various kinematic properties of the Galactic globular cluster system.

Figure: effective radii of globular cluster systems vs total mass of host halos.

We validate the near-linear globular cluster mass-halo mass correlation down to M_h ~ 10⁸ M_sun, where the majority of dwarf galaxies do not host any cluster, using our globular cluster formation model. By studying two Fornax-like satellites in the simulations, we reproduce the radial profile of globular clusters in Fornax and show that observational samples can be notably biased by incompleteness below detection limit and at large radii.

Figure: near-linear globular cluster mass-halo mass correlation.

We generate a mock catalogue of globular clusters reproducing the total mass, mass function, metallicity distribution, radial profile, and velocity dispersion of the Galactic globular cluster systems by applying our globular cluster formation model to simulated Milky Way-like galaxies. Based on this catalogue, we examine various clustering methods to categorize the progenitors of globular clusters, using their age, chemical, and kinematic properties, and subsequently apply the same methods and properties to Galactic clusters.

Figure: classification of the Milky Way globular clusters shown in the integral of motion plane.

We develop a new particle spray algorithm to model the formation of globular cluster streams. The algorithm ejects stream tracer particles based on 6D phase space distributions calibrated to N-body simulations. It successfully matches the morphology and kinematics of simulated streams with higher accuracy than most existing particle spray methods. The new algorithm is implemented in galactic dynamics codes agama, gala, galax, and galpy for public use.

Figure: positions and velocity vectors of escaped stream particles near the Lagrange points.

By comparing the densities of streams recently discovered by Gaia DR3 with mock streams generated using our new particle spray algorithm, we present the first direct measurement of mass loss rates for 12 Galactic globular clusters. We further explore correlations between the mass loss rate and key GC properties, confirming theoretical predictions from N-body simulations.

Figure: mass loss rates of 12 Galactic globular clusters plotted against cluster mass.

Based on the cosmic light speed variation, we find a novel pre-burst stage for gamma-ray bursts. We also employ a primary clustering method of machine learning to classify this stage with the data from the Fermi telescope. The work was completed in 2019 but was accepted for publication in 2021 due to the COVID-19 pandemic.

Figure: a classification of gamma-ray burst photons that distinguishes pre-burst from main-burst.