NIHAO - XI. Formation of ultra-diffuse galaxies by outflows

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  • Arianna Di Cintio
  • Chris B. Brook
  • Aaron A. Dutton
  • Andrea V. Macciò
  • Aura Obreja
  • Avishai Dekel

We address the origin of ultra-diffuse galaxies (UDGs), which have stellar masses typical of dwarf galaxies but effective radii of Milky Way-sized objects. Their formation mechanism, and whether they are failed L* galaxies or diffuse dwarfs, are challenging issues. Using zoomin cosmological simulations from the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project, we show that UDG analogues form naturally in dwarf-sized haloes due to episodes of gas outflows associated with star formation. The simulated UDGs live in isolated haloes of masses 1010-11 M⊙, have stellar masses of 107-8.5 M⊙, effective radii larger than 1 kpc and dark matter cores. They show a broad range of colours, an average Sérsic index of 0.83, a typical distribution of halo spin and concentration, and a non-negligible HI gas mass of 107-9 M⊙, which correlates with the extent of the galaxy. Gas availability is crucial to the internal processes which form UDGs: feedback-driven gas outflows, and subsequent dark matter and stellar expansion, are the key to reproduce faint, yet unusually extended, galaxies. This scenario implies that UDGs represent a dwarf population of low surface brightness galaxies and should exist in the field. The largest isolated UDGs should contain more HI gas than less extended dwarfs of similar M*.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society: Letters
Volume466
Issue number1
Pages (from-to)L1-L6
ISSN1745-3933
DOIs
Publication statusPublished - 21 Mar 2017

    Research areas

  • Galaxies: dwarf, Galaxies: evolution, Galaxies: formation, Galaxies: haloes

Links

ID: 196949707