The Radio Quiescence of Active Galaxies with High Accretion Rates
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≡f6cm/f4400Å of 2.8. The 3 σ upper limits for the remaining nondetections correspond to radio powers from 3×1020 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 NLS1s 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 Lbol/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 Lbol/LEdd.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2006
- DOI:
- 10.1086/497905
- arXiv:
- arXiv:astro-ph/0509198
- Bibcode:
- 2006ApJ...636...56G
- Keywords:
-
- Galaxies: Active;
- Galaxies: Jets;
- Galaxies: Nuclei;
- Galaxies: Seyfert;
- Galaxies: Structure;
- Radio Continuum: Galaxies;
- Astrophysics
- E-Print:
- To appear in ApJ