MUltiplexed Survey Telescope (MUST) Science White Paper I: Overview of Large-Scale Structure Cosmology in the Era of Stage-V Spectroscopic Surveys

TL;DR

MUST is a 6.5-meter telescope designed for large-scale, multiplexed spectroscopic surveys aiming to map over 100 million galaxies and quasars up to redshift 5.5 in the 2030s, enabling key cosmological investigations.

Contribution

This paper introduces the conceptual design and scientific goals of MUST, the first Stage-V spectroscopic survey telescope for large-scale structure cosmology.

Findings

MUST can observe over 20,000 targets simultaneously.

Fisher forecasts show MUST can address dark energy and gravity theories.

Initial target selection algorithms cover a wide redshift range.

Abstract

The MUltiplexed Survey Telescope (MUST) is a 6.5-meter telescope under development. Dedicated to highly-multiplexed, wide-field spectroscopic surveys, MUST observes over 20,000 targets simultaneously using 6.2-mm pitch positioning robots within a ~5 deg$^2$ field of view. MUST aims to conduct the first Stage-V spectroscopic survey in the 2030s, mapping the 3D Universe with over 100 million galaxies and quasars, spanning from the nearby Universe to a redshift of z ~ 5.5, corresponding to approximately 1 billion years after the Big Bang. To cover this extensive redshift range, we present an initial conceptual target selection algorithm for different types of galaxies, ranging from local bright galaxies and luminous red galaxies to emission-line galaxies, and high-redshift (2 < z < 5.5) Lyman-break galaxies. Using Fisher forecasts, we demonstrate that MUST can address fundamental questions in cosmology, including the nature of dark energy, tests of gravity theories, and investigations into primordial physics. This is the first paper in the series of science white papers for MUST, with subsequent developments focusing on additional scientific cases such as galaxy and quasar evolution, Milky Way physics, and dynamic phenomena in the time-domain Universe.