Ultra-Diffuse Galaxy Formation in Cosmic Structures
Summary
Ultra-diffuse galaxies (UDGs) are a class of low-surface-brightness systems characterised by large effective radii and diffuse stellar distributions. Despite stellar masses comparable to dwarf galaxies, their sizes can rival those of L* galaxies, rendering them almost invisible to conventional surveys. Observational studies and cosmological simulations have revealed multiple formation pathways: some UDGs arise in high-spin dark matter haloes that naturally produce extended stellar discs; others result from internal processes such as early supernova feedback that flattens gas profiles and inhibits central star formation; and a significant fraction are sculpted by environmental effects, with tidal stripping and heating in groups or clusters puffing up initially compact dwarfs into the ultra-diffuse regime. UDGs inhabit a wide range of environments, from isolation to rich clusters, offering unique probes of dark matter properties, baryonic feedback efficiency and galaxy evolution in the low-surface-brightness frontier. Their abundance and distribution bear on cosmological models, while their extreme characteristics challenge our understanding of galaxy formation and the interplay between dark and luminous matter.
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Ultra-Diffuse Galaxy Formation in Cosmic Structures publication trend
The graph below shows the total number of articles in ultra-diffuse galaxy formation in cosmic structures across all publications each year (not limited to Nature Index journals).
Technical terms
Ultra-diffuse galaxy (UDG): a galaxy with a large effective radius (>1.5 kpc) and very low central surface brightness (μ0,g ≳ 24 mag arcsec−2).
Effective radius (Re): the radius enclosing half of a galaxy’s total light, indicating its spatial extent.
Tidal stripping: removal of stars and gas from a galaxy due to gravitational forces in a dense environment.
Dark matter halo: diffuse, invisible mass surrounding galaxies that dominates their gravitational potential.
References
- Systematically Measuring Ultra-diffuse Galaxies (SMUDGes). V. The Complete SMUDGes Catalog and the Nature of Ultradiffuse Galaxies. The Astrophysical Journal Supplement Series (2023).
- The formation of ultra-diffuse galaxies in cored dark matter haloes through tidal stripping and heating. Monthly Notices of the Royal Astronomical Society (2019).
- A Universe of ultradiffuse galaxies: theoretical predictions from ΛCDM simulations. Monthly Notices of the Royal Astronomical Society (2017).
- Ultra-diffuse galaxies in the Auriga simulations. Monthly Notices of the Royal Astronomical Society (2019).
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