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Colloquium
Clustering of Emission Line Galaxies Scrutinised with Hydrodynamical Simulations

Abstract

In order to investigate the structure formation and evolution in the distant Universe, emission line galaxies (ELGs) are suitable targets for upcoming spectroscopic surveys (e.g., PFS, Euclid, DESI). Since massive OB-type stars source the strong emission line, ELGs generally are young star-forming galaxies. Thus, the clustering nature of ELGs is expected to be quite different from that of luminous red galaxies, which are widely studied in past spectroscopic observations. In order to address the clustering properties of ELGs, we utilise galaxy formation hydrodynamical simulations: IllustrisTNG. We have developed the method to simulate emission line intensity with stellar population synthesis code PEGASE-3. In simulations, we can directly investigate the relationship between the properties of ELGs and host halos and measure the cosmological statistics, e.g., projected correlation function. With these high-fidelity mock ELG catalogues, we measure the halo occupation distribution (HOD) and find the signature of infalling distinct halo contribution as suggested by semi-analytic simulations. Next, we measure the projected correlation function and infer HOD parameters with the correlation function. Then, we discuss whether the true HOD can be reproduced from the projected correlation function measurement. Finally, we present the ongoing analysis of the three-dimensional anisotropic power spectra of simulated ELGs. We infer cosmological parameters from the power spectra and directly compare them with the input values used in simulations. This ``cosmology challenge'' analysis examines which theoretical template can correctly reproduce the correct cosmological parameters.