Affiliation: Curtin institute of radio astronomy

Contribution: Oral

Title: Interpreting the reionization of the universe through cosmic noon analogs. Addressing the SED modelling approach.

Abstract: Modern instruments are rapidly eliminating the observational constraints that once limited our understanding of the early universe. The JWST has enriched high-redshift catalogs with deep rest-optical and IR photometry, while increasingly sophisticated SED modeling tools interpret the underlying ionizing photon production (ξ_ion) and its escape (f_esc). However, the interface between observations and models is complex, and our interpretation of the data relies heavily on the applied star, gas, and dust models. In this talk, we address how model assumptions affect our interpretation of the observations and, consequently, our conclusions about the galaxies that may have reionized the universe. 

We explore a subset of reionization-era analogs at 2.5 < z < 4 with similarly extreme [OIII]+[Hb] equivalent widths. Firstly, we establish their selection as analogous galaxies (log(M*/Msun) ~ 8.9, sSFR ~ 10^-8 Gyr^-1, UV slope ~ -1.7) without the influence of IGM opacity or photometric constraints. Then, I will discuss their ionizing photon production efficiency and how it is influenced by SED model assumptions, such as star formation history (SFH), stellar population synthesis (SPS), and dust attenuation models. For example, we find that SFH models can change ξ_ion by more than 0.5 dex, which completely redefines the reionization budget and timeframe.

This contribution can be found here (pdf).