ESpRESSO: Modelling realistic crowded scenes for deep Roman Space Telescope grism spectroscopy

Abstract We describe the software package ESpRESSO - [E]xtragalactic [Sp]ectroscopic [R]oman [E]mulator and [S]imulator of [S]ynthetic [O]bjects, created to emulate the slitless spectroscopic observing modes of the Nancy Grace Roman Space Telescope (Roman) Wide Field Instrument (WFI). We combine archival Hubble Space Telescope (HST) imaging data of comparable spatial resolution with model spectral energy distributions to create a data-cube of flux density as a function of position and wavelength. ESpRESSO is designed to generate grism simulations for any Roman WFI SCA using detector-specific optical solutions; in this paper, the simulations are limited by the sky area of the deepest available input imaging and therefore focus primarily on SCA5, with a foreground scene spanning approximately two SCAs. We also demonstrate the ability to inject custom sources using the described tools and pipelines. In addition, we show that spectral features such as emission line pairs are unlikely to be mistaken as off order contaminating features and vice versa. These simulated scenes can be used in developing future spectral data analysis tools.