UV luminosity function of high-z galaxies using zZ-dependent IMF
Speaker: Keita Fukushima (Seoul National University)
Abstract:
To understand the overall picture of galaxy formation and evolution, it is essential to study the statistical properties of galaxies. The UV luminosity function of galaxies at redshift z>10, observed by the James Webb Space Telescope (JWST), shows that the bright end is more than an order of magnitude higher in number density than expected from the Schechter function. One theoretical model that explains this uses a top-heavy initial mass function (IMF) with an overabundance of massive stars.
In this study, we model an IMF dependent on redshift z and metallicity Z (Chon et al. 2022) and use the spectral synthesis code FSPS (Conroy, Gunn, & White 2009) to create spectral templates for star clusters. The zZ dependent IMF becomes top-heavy compared to the Kroupa IMF at low metallicities and high redshifts. In such cases, the UV luminosity is higher for young star clusters than with the Kroupa IMF but becomes lower at 10 Gyr due to a lower fraction of low-mass stars.
A galaxy formation model was developed by applying a semi-analytic model with metal enrichment to the merger trees obtained from the Shin Uchuu Simulation (Ishiyama et al. 2021). We then applied the spectral templates to this model to derive the UV luminosity function and compared it with observations, discussing the impact of the top-heavy IMF.