Simulating continuum-based redshift measurement in the \textit{Roman's} High Latitude Spectroscopy Survey

TL;DR

This study evaluates the Roman Space Telescope's ability to measure redshifts of quiescent galaxies using simulated slitless spectroscopy, focusing on continuum detection and survey optimization for cosmology.

Contribution

It demonstrates the potential of Roman's G150 grism for continuum-based redshift measurement of quiescent galaxies and assesses survey parameters affecting redshift recovery.

Findings

Redshift recovery completeness ≥50% for galaxies brighter than F158=20.2 mag.

Survey parameters like exposure time significantly impact redshift accuracy.

Roman's grism can effectively measure redshifts in the 0.5 ≤ z ≤ 2.5 range.

Abstract

We investigate the capability of the \textit{Nancy Grace Roman Space Telescope's (Roman)} Wide-Field Instrument (WFI) G150 slitless grism to detect red, quiescent galaxies based on the current reference survey. We simulate dispersed images for \textit{Roman} reference High-Latitude Spectroscopic Survey (HLSS) and analyze two-dimensional spectroscopic data using the grism Redshift and Line Analysis (\verb|Grizli|) software. This study focus on assessing \textit{Roman} grism's capability for continuum-level redshift measurement for a redshift range of $0.5 \leq z \leq 2.5$. The redshift recovery is assessed by setting three requirements of: $\sigma_z = \frac{\left|z-z_{\mathrm{true}}\right|}{1+z}\leq0.01$, signal-to-noise ratio (S/N) $\geq 5$ and the presence of a single dominant peak in redshift likelihood function. We find that, for quiescent galxaies, the reference HLSS can reach a redshift recovery completeness of $\geq50\%$ for F158 magnitude brighter than 20.2 mag. We also explore how different survey parameters, such as exposure time and the number of exposures, influence the accuracy and completeness of redshift recovery, providing insights that could optimize future survey strategies and enhance the scientific yield of the \textit{Roman} in cosmological research.