Linear bias and halo occupation distribution of emission line galaxies from Nancy Grace Roman Space Telescope

TL;DR

This paper measures the linear galaxy bias and halo occupation distribution of emission line galaxies from the Nancy Grace Roman Space Telescope's survey, providing essential data for cosmological forecasts.

Contribution

It introduces new bias and halo occupation measurements for Hα and [OIII] emission line galaxies using galaxy mocks, aiding future cosmological analyses.

Findings

Bias increases linearly with redshift for both galaxy types.

Bias functions are approximately 0.88z+0.49 for Hα and 0.98z+0.49 for [OIII].

Halo occupation distributions are characterized for these emission line galaxies.

Abstract

We present measurements of the linear galaxy bias of H$\alpha$ and [OIII] emission line galaxies (ELGs) for the High Latitude Spectroscopic Survey (HLSS) of Nancy Grace Roman Space Telescope, using galaxy mocks constructed using semi-analytical model for galaxy formation, {\it Galacticus}, with a large cosmic volume and redshift coverage. We compute the two-point statistics of galaxies in configuration space and measure linear bias within scales of $10\sim50 h^{-1}$Mpc. We adopt different selection algorithms to investigate the impact of the Roman line flux cut, as well as the effect of dust model used to calibrate Galacticus, on the bias measurements. We consider galaxies with H$\alpha$ and [OIII] emissions over the redshift range $1<z<3$, as specified by the current baseline for the Roman HLSS. We find that the linear bias for the H$\alpha$ and [OIII] ELGs can be expressed as a linear function with respect to redshift: $b \simeq 0.88z+0.49$ for H$\alpha$ $(1<z<2)$, and $b \simeq 0.98z+0.49$ for [OIII] $(2<z<3)$. We have also measured the Halo Occupation Distributions of these H$\alpha$ and [OIII] emission line galaxies to understand their distribution within dark matter halos. Our results provide key input to enable the reliable forecast of dark energy and cosmology constraints from Roman.