The radio quiescence of active galaxies with high accretion rates

Jenny E. Greene, Luis C. Ho, James S. Ulvestad

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73 Scopus citations

Abstract

We present 6 cm Very Large Array observations of the Greene & Ho sample of 19 low-mass active galaxies with high accretion rates. This is one of the only studies of a uniform sample of narrow-line Seyfert 1 (NLS1) galaxies with such high sensitivity and resolution. Although we detect only one source, the entire sample is very radio quiet down to strong limits. GH 10 was found to have a radio power of 8.5 × 1021 W Hz-1 and a ratio R = f6 cm f4400 Å of 2.8. The 3 σ upper limits for the remaining nondetections correspond to radio powers from 3 × 10 20 to 8 × 1021 W Hz-1 and 0.47 < R < 9.9. Stacking all nondetections yields an even stronger upper limit of R < 0.27. An assessment of existing observations in the literature confirms our finding that NLS1 s are consistently radio-quiet, with a radio-loud fraction of 0%-6%, which is significantly lower than the 10%-20% observed in the general quasar population. By analogy with stellar mass black holes, we argue that AGNs undergo a state transition at Ibol/LEdd ≈ 0.01. Below this value a radiatively inefficient accretion flow effectively drives an outflow, which disappears when the flow turns into an optically thick, geometrically thin disk, or a radiation pressure - dominated slim disk at still higher Zbol/LEdd.

Original languageEnglish (US)
Pages (from-to)56-62
Number of pages7
JournalAstrophysical Journal
Volume636
Issue number1 I
DOIs
StatePublished - Jan 1 2006

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Galaxies: Seyfert
  • Galaxies: active
  • Galaxies: jets
  • Galaxies: nuclei
  • Galaxies: structure
  • Radio continuum: galaxies

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