Kiloparsec-scale Radio Structures in Narrow-line Seyfert 1 Galaxies
Abstract
We report the finding of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters of the Very Large Array, which increases the number of known radio-loud NLS1s with kpc-scale structures to six, including two γ-ray-emitting NLS1s (PMN J0948+0022 and 1H 0323+342) detected by the Fermi Gamma-ray Space Telescope. The detection rate of extended radio emissions in NLS1s is lower than that in broad-line active galactic nuclei (AGNs) with a statistical significance. We found both core-dominated (blazar-like) and lobe-dominated (radio-galaxy-like) radio structures in these six NLS1s, which can be understood in the framework of the unified scheme of radio-loud AGNs that considers radio galaxies as non-beamed parent populations of blazars. Five of the six NLS1s have (1) extended radio luminosities suggesting jet kinetic powers of >~ 1044 erg s-1, which is sufficient to make jets escape from hosts' dense environments; (2) black holes of >~ 107 M ⊙, which can generate the necessary jet powers from near-Eddington mass accretion; and (3) two-sided radio structures at kpc scales, requiring expansion rates of ~0.01c-0.3c and kinematic ages of >~ 107 years. On the other hand, most typical NLS1s would be driven by black holes of <~ 107 M ⊙ in a limited lifetime of ~107 years. Hence, the kpc-scale radio structures may originate in a small window of opportunity during the final stage of the NLS1 phase just before growing into broad-line AGNs.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2012
- DOI:
- 10.1088/0004-637X/760/1/41
- arXiv:
- arXiv:1210.1303
- Bibcode:
- 2012ApJ...760...41D
- Keywords:
-
- galaxies: active;
- galaxies: individual: PMN J0948+0022 SDSS J120014.08–004638.7 SDSS J145041.93+591936.9 FBQS J1644+2619 1H 0323+342 PKS 0558–504;
- galaxies: jets;
- galaxies: Seyfert;
- gamma rays: galaxies;
- radio continuum: galaxies;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 12 pages, 3 figures, 3 tables, accepted for publication in the Astrophysical Journal