AGN in dwarf galaxies: frequency, triggering processes and the plausibility of AGN feedback

Sugata Kaviraj, Garreth Martin, Joseph Silk

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While active galactic nuclei (AGN) are considered to be key drivers of the evolution of massive galaxies, their potentially significant role in the dwarf-galaxy regime (M < 10 9 M ) remains largely unexplored. We combine optical and infrared data, from the Hyper Suprime-Cam (HSC) and the Wide-field Infrared Explorer, respectively, to explore the properties of ∼800 AGN in dwarfs at low redshift (z < 0.3). Infrared-selected AGN fractions are ∼10-30 per cent in dwarfs, which, for reasonable duty cycles, indicates a high black hole (BH)-occupation fraction. Visual inspection of the deep HSC images indicates that the merger fraction in dwarf AGN (∼6 per cent) shows no excess compared to a control sample of non-AGN, suggesting that the AGN-triggering processes are secular in nature. Energetic arguments indicate that, in both dwarfs and massive galaxies, bolometric AGN luminosities (L AGN) are significantly greater than supernova luminosities (L SN). L AGN/L SN is, in fact, higher in dwarfs, with predictions from simulations suggesting that this ratio only increases with redshift. Together with the potentially high BH-occupation fraction, this suggests that if AGN feedback is an important driver of massive-galaxy evolution, the same is likely to be true in the dwarf regime, contrary to our classical thinking.

Original languageEnglish
Article numberslz102
Pages (from-to)L12–L16
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date26 Jun 2019
Publication statusPublished - 1 Oct 2019


  • astro-ph.GA
  • galaxies: Dwarf
  • galaxies: Evolution
  • galaxies: Active


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