AGN feedback causes downsizing

Evan Scannapieco, Joseph Silk, Rychard Bouwens

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


We study the impact of outflows driven by active galactic nuclei (AGNs) on galaxy formation. Outflows move into the surrounding intergalactic medium (IGM) and heat it sufficiently to prevent it from condensing onto galaxies. In the dense, high-redshift IGM, such feedback requires a highly energetic outflow, driven by a large AGN. However, in the more tenuous low-redshift IGM, equivalently strong feedback can be achieved by less energetic winds (and thus smaller galaxies). Using a simple analytic model, we show that this leads to the antihierarchical quenching of star formation in large galaxies, consistent with current observations. At redshifts prior to the formation of large AGNs, galaxy formation is hierarchical and follows the growth of dark matter halos. The transition between the two regimes lies at the z ≈ 2 peak of AGN activity.

Original languageEnglish (US)
Pages (from-to)L13-L16
JournalAstrophysical Journal
Issue number1 II
StatePublished - Dec 10 2005
Externally publishedYes


  • Galaxies: evolution
  • Large-scale structure of universe
  • Quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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