Shingo Hirano

Shingo Hirano

Astronomer / Astrophysicist

Research

My research connects cosmological structure formation, star formation physics, and compact-object origins using numerical simulations and observations.

This simulation video highlights the kind of numerical work behind the projects summarized below.

For each theme below:

  1. Problem
  2. Approach
  3. Key findings
  4. Context
  5. Future outlook

1. First Stars: Individual Formation

  1. How do primordial protostars accrete, fragment, and reach their final masses?
  2. 3D radiation-hydrodynamics and MHD simulations from cloud collapse to protostellar growth.
  3. Final masses depend strongly on accretion history and environment; magnetic amplification can suppress disk fragmentation.
  4. These constraints are important for interpreting early stellar populations in the JWST era.
  5. I will extend these models to metallicity-dependent regimes and quantify when disk fragmentation, magnetic braking, and protostellar feedback change their relative importance. A key goal is to provide physically calibrated inputs for first-galaxy simulations.

2. First Stars: Population and Statistics

  1. What are the statistical properties of Pop III formation across many halos?
  2. Large-sample cosmological simulations including environmental effects (e.g., streaming motions, radiation).
  3. Critical halo scales and core mass functions are environment dependent, indicating no single universal Pop III pathway.
  4. Population-level modeling now feeds directly into high-redshift galaxy and reionization studies.
  5. I will expand from halo-by-halo statistics to first-galaxy populations, including environment-dependent IMF variation and halo-to-halo scatter. This will enable direct links to fossil signatures in Milky Way metal-poor stars.
  • SH, MNRAS (2025) “Formation of first star clusters under the supersonic gas flow - II. Critical halo mass and core mass function”
  • SH et al., MNRAS (2023) “Formation of first star clusters under the supersonic gas flow - I. Morphology of the massive metal-free gas cloud”
  • SH et al., MNRAS (2015) “Primordial star formation under the influence of far ultraviolet radiation: 1540 cosmological haloes and the stellar mass distribution”

3. Supermassive Black Hole Seeds

  1. How can SMBH seeds form rapidly in the early Universe?
  2. Cosmological simulations of atomic-cooling clouds with gas streaming, thermal evolution, and magnetic effects.
  3. Streaming and magnetic effects can open efficient pathways to massive seed formation via supermassive-star channels.
  4. This provides testable seed scenarios for emerging high-redshift AGN constraints.
  5. I will perform systematic comparisons of multiple seed channels within a single cosmological framework, and predict host-galaxy properties and observables for rapidly accreting young black holes, including LRD-like populations.

4. Dark Matter and Early Structure Formation

  1. How do dark matter microphysics and interactions affect first structure formation?
  2. Comparative simulations of standard and non-standard DM scenarios (e.g., baryon-DM scattering, ultra-light DM).
  3. DM physics can shift collapse timing, central density structure, and first-star conditions in measurable ways.
  4. Early-universe star formation is becoming a practical probe of dark matter models.
  5. I will test how dark-matter-dependent collapse histories propagate into first-galaxy diversity and black-hole seed formation efficiency. The aim is to identify observable diagnostics that can discriminate between dark matter scenarios.

5. Present-day Star Formation (Protostars, Disks, Outflows)

  1. How do infall, rotation, magnetic fields, and outflows shape Class 0/I protostellar environments?
  2. 3D MHD simulations and kinematic interpretation of protostellar observations.
  3. Misalignment and non-axisymmetric flows can bias simple mass estimates; one protostar can drive multiple outflow components.
  4. This supports direct theory-observation comparisons in the ALMA era.
  5. I will use present-day protostellar systems as a calibration bridge for core star-formation physics, then transfer validated MHD/radiation prescriptions to low-metallicity and primordial environments.

Full Publication Lists