4.7 Article

EDGE: What shapes the relationship between H i and stellar observables in faint dwarf galaxies?

Journal

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 511, Issue 4, Pages 5672-5681

Publisher

OXFORD UNIV PRESS
DOI: 10.1093/mnras/stac502

Keywords

methods: numerical; galaxies: dwarf; galaxies: evolution; galaxies: haloes; galaxies: structure

Funding

  1. Beecroft Fellowship - Adrian Beecroft
  2. Knut and Alice Wallenberg Foundation
  3. Swedish Research Council [2014-5791, 2019-04659]
  4. Royal Physiographic Society in Lund
  5. Royal Society
  6. UKRI Science and Technology Facilities Council (STFC) [ST/R505134/1]
  7. European Union's Horizon 2020 research and innovation programme [818085 GMGalaxies]
  8. BEIS capital funding via STFC [ST/K000373/1, ST/R002363/1]
  9. STFC DiRAC Operations grant [ST/R001014/1]
  10. UCL Cosmoparticle Initiative

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The interplay between feedback and mass-growth histories introduces scatter in the relationship between stellar and neutral gas properties of faint dwarf galaxies. Simulations show that dwarf galaxies with stellar masses between 10^5 to 10^6 solar masses exhibit bimodality in their cold gas content, either being H I-rich or H I-deficient. Stellar feedback plays a significant role in creating disturbed and time-variable neutral gas distributions.
We show how the interplay between feedback and mass-growth histories introduces scatter in the relationship between stellar and neutral gas properties of field faint dwarf galaxies (M-*less than or similar to 10(6) M-circle dot). Across a suite of cosmological, high-resolution zoomed simulations, we find that dwarf galaxies of stellar masses 10(5) <= M-* <= 106 M-circle dot are bimodal in their cold gas content, being either H I-rich or H I-deficient. This bimodality is generated through the coupling between (i) the modulation of H I contents by the background of ultraviolet radiation (UVB) at late times and (ii) the significant scatter in the stellar-to-halo mass relationship induced by reionization. Furthermore, our H I-rich dwarfs exhibit disturbed and time-variable neutral gas distributions primarily due to stellar feedback. Over the last four billion years, we observe order-of-magnitude changes around the median M-H I, factor-of-a-few variations in H I spatial extents, and spatial offsets between H I and stellar components regularly exceeding the galaxies' optical sizes. Time variability introduces further scatter in the M-*-M-H I relation and affects a galaxy's detectability in H I at any given time. These effects will need to be accounted for when interpreting observations of the population of faint, H I-bearing dwarfs by the combination of optical and radio wide, deep surveys.

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