Why the Northern Hemisphere Needs a 30-40m Telescope and the Science at Stake: Ultra-Low-Mass Dwarf Galaxies Across the Boreal Cosmic Web

TL;DR

This paper argues that a northern 30–40 m telescope equipped with a multiplexed optical integral-field spectrograph is essential to study ultra-low-mass dwarfs across diverse environments, from cluster cores to filaments. By conducting a deep Coma survey alongside targeted observations in Virgo, groups, and low-density regions, it outlines how spatially resolved spectroscopy can yield chemo-dynamical maps, dynamical masses, and orbital histories, thereby testing feedback, reionization, and environmental-quenching scenarios in the lowest-mass regime. The work positions dwarf galaxies as precision probes of both galaxy formation and fundamental physics, linking near-field cosmology to cosmological models and dark-matter theories, and highlights synergies with northern surveys to enable a cohesive, environment-spanning census. The proposed capabilities would transform our understanding of how internal and external processes shape galaxy evolution at the smallest scales and across the cosmic web.

Abstract

Dwarf galaxies dominate the galaxy population in the nearby Universe and occupy the regime where feedback, reionization, and environment exert their strongest influence on galaxy formation. Despite their importance, detailed spectroscopic constraints on the faintest dwarfs are currently limited to a handful of systems in the Local Volume, leaving the role of large-scale environment essentially unexplored at ultra-low stellar masses. A northern 30-40m class telescope equipped with a multiplexed optical integral-field spectrograph will enable a systematic, spatially resolved spectroscopic census of dwarf galaxies with $M_\star \sim 10^{5}-10^{7} M_\odot$ across a wide range of environments. A deep survey of the Coma Cluster, combined with targeted observations of dwarfs in clusters, groups, filaments, and low-density regions, will map star formation histories, chemical enrichment, and internal kinematics at unprecedented depth. This program will directly test models of dark-matter physics, early-Universe feedback, and environmental quenching in the lowest-mass galaxies, establishing dwarf galaxies as precision probes of both galaxy formation and fundamental physics.