Affiliation: The University of Melbourne

Contribution: Oral

Title:Predicting luminosity function and [OIII]𝜆5007/H𝛽 flux ratio for the galaxy ISM at high-redshifts

Abstract: We present emission line flux ratio [OIII]𝜆5007/H𝛽 diagnostics for the interstellar properties of recently discovered galaxies at 𝑧 ∼ 7 – 9 using the MAPPINGS V v5.2.0 photoionization modelling code. We provide tabulated OIII/H𝛽 diagnostics, together with empirical fitted relations, in the parameter space of physical properties describing high redshift galaxies. Properties such as pressure and ionization parameter are thought to evolve towards high redshift, and in order to determine the range of expected interstellar conditions, we construct a physical model for emission line galaxy properties. This is achieved by extending previous modelling of the Star Formation Rate Density (SFRD) function, accounting for major mergers and supernova (SN) feedback to calculate emission line luminosity and flux ratios. We also incorporate the impact of turbulence on galactic discs, and its influence on various physical properties, including the ionization parameter. To validate emission line predictions we calculate the [O III]𝜆5007 line luminosity and its dependence on UV luminosity, as well as the flux ratio [OIII]𝜆5007/H𝛽 and its variation with the line luminosity finding that both reproduce recent JWST observations from the FRESCO survey. We also use our model to predict the number counts of emission line galaxies across a range of redshift. Finally, we show that the dependence of flux ratio on luminosity provides a potential diagnostic for the presence of turbulence in galactic disks.

This contribution can be found here (pdf).