# [OII] emitters in MultiDark-Galaxies and DEEP2

## TL;DR

This study compares semi-analytic galaxy formation models with observational data to evaluate methods of estimating [OII] emission line luminosities and their impact on galaxy clustering predictions.

## Contribution

It introduces a new approach to estimate [OII] luminosities from average SFRs and global properties, validating its accuracy and exploring its effects on galaxy clustering.

## Key findings

- Post-processing L[OII] from average SFRs is accurate below 10^{42.2} erg s^{-1}.
- L[OII] correlates strongly with u and g broad-band magnitudes.
- Clustering amplitude remains consistent regardless of L[OII] derivation method.

## Abstract

We use three semi-analytic models (SAMs) of galaxy formation and evolution, run on the same 1$h^{-1}$Gpc MultiDark Planck2 cosmological simulation, to investigate the properties of [OII] emission line galaxies in the redshift range $0.6<z<1.2$. We compare model predictions with different observational data sets, including DEEP2--Firefly galaxies with absolute magnitudes. We estimate the [OII] luminosity, L[OII], using simple relations derived both from the models and observations and also using a public code. This code ideally uses as input instantaneous star formation rates (SFRs), which are only provided by one of the SAMs under consideration. We use this SAM to study the feasibility of inferring galaxies' L[OII] for models that only provide average SFRs. We find that the post-processing computation of L[OII] from average SFRs is accurate for model galaxies with dust attenuated L[OII]$\lesssim10^{42.2}$erg s$^{-1}$ ($<5\%$ discrepancy). We also explore how to derive the [OII] luminosity from simple relations using global properties usually output by SAMs. Besides the SFR, the model L[OII] is best correlated with the observed-frame $u$ and $g$ broad-band magnitudes. These correlations have coefficients (r-values) above 0.64 and a dispersion that varies with L[OII]. We use these correlations and an observational one based on SFR and metallicity to derive L[OII]. These relations result in [OII] luminosity functions and halo occupation distributions with shapes that vary depending on both the model and the method used. Nevertheless, for all the considered models, the amplitude of the clustering at scales above 1$h^{-1}$Mpc remains unchanged independently of the method used to derive L[OII].