Young galaxies as tracers and agents of cosmic reionization

Introduction

The identification of the first galaxies in the early Universe has been an expanding frontier of observational astrophysics. Reionization marks the last major phase transition of matter in the Universe and its completion had a crucial impact on the formation of the smallest galaxies.

Importance of Reionization

Reionization is therefore the first landmark of the influence that feedback from star formation had on structure formation. While reionization roughly encapsulated the first Gyr of cosmic time, the precise timing, topology, and the sources of ionizing photons are unknown.

Key Questions

• Did reionization proceed rapidly or gradually?
• Was it driven by rare bright galaxies or numerous faint ones?

Current Limitations

The main limitation to our understanding is our little knowledge of the properties of galaxies in the early Universe.

Advancements with JWST

Now, thanks to the long-awaited James Webb Space Telescope (JWST), this field can transition into the study of the characteristics of these first galaxies and the assessment of their impact on their environment.

Technical Capabilities

With its new technical capabilities, JWST will enable:

• The identification of thousands of faint galaxies in the early Universe.
• The measurement of the detailed properties of their stellar populations and interstellar medium.

Project Goals

My StG will benefit from my early access to JWST to obtain a complete census of the young galaxy population with emission-line surveys in the first 3 Gyr of cosmic time.

Methodology

I will use unprecedented observational techniques in survey fields that enable direct measurements of the connection between galaxies and intergalactic gas.

Research Focus

Based on a multi-angled approach, I will assess the role of young galaxies as agents and tracers of reionization. My team will:

1. Measure the total ionizing budget from young galaxies in the early Universe.
2. Self-consistently trace the topology and timing of reionization on global and local scales.

Legacy and Future Endeavours

This project will yield a legacy that paves the way for future endeavours with the Extremely Large Telescopes and the Square Kilometre Array.