Poster Presentation

Chemical Enrichment in the First Galaxies and Extremely Metal-Poor Galaxies (EMPGs)

Author(s): Keita Fukushima, Kentaro Nagamine (Osaka University)

Presenter: Keita Fukushima (Osaka University)

The chemical abundance is a good tracer of the star formation history of galaxies, and the relationship between the helium abundance (He/H) and metallicity can be used to determine the primordial helium abundance of Big Bang nucleosynthesis (Matsumoto et al. 2023). The JWST has identified galaxies spectroscopically at z>10, and extremely metal-poor galaxies (EMPGs) have also been observed in the local Universe. We need better theoretical understanding of the correlation between the formation process and chemical evolution of low-metallicity galaxies to explain the observed chemical abundance of EMPGs.

In this work, we investigate the chemical enrichment history of low-metallicity galaxies by one-zone model calculations and cosmological hydrodynamic simulations coupled with the chemical evolution library CELib. Our one zone model shows that the model with more active star formation with specific star formation rate (sSFR) comparable to the observed EMPGs has a lower He/H for the same metallicity. This is because He is more abundant in AGB stars. We also investigate the first galaxy formation by zoom-in high-resolution simulation using the cosmological SPH code GADGET3-Osaka. We find that the gas with high He/H has high-temperatures, suggesting the impact of the supernova feedback. The other chemical abundance observed in EMPG, such as Fe/O and N/O, are also discussed.