2004/06/25 by Xinwu Cao
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/423228
published as Astrophys.J. 613 (2004) 716-724 · 9 pages, accepted for publication in ApJ
arxiv created 2004/06/25 · openalex publication_date 2004/10/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We use a sample of radio-loud active galactic nuclei (AGNs) with estimated central black hole masses to explore AGN jet-formation mechanisms. The jet power of AGNs is estimated from their extended radio luminosity. We find that the jets in several AGNs of this sample are too powerful to be extracted from the standard thin accretion disks or rapidly spinning black holes surrounded by standard thin disks. If advection-dominated accretion flows (ADAFs) are present in these AGNs, their bright optical continuum luminosity cannot be produced by pure ADAFs because of their low accretion rates and low radiation efficiency, unless the ADAFs transit to standard thin disks at some radii R tr . If this is the case, we find that dimensionless accretion rates = / Edd as high as ≥0.05, and a transition from ADAFs to standard thin disks at rather small radii, ~20 GM bh / c 2 , are required to explain their bright optical continuum emission. We propose that the disk-corona structure is present in at least some AGNs in this sample. The plasmas in the corona are very hot, and the pressure scale height of the corona H c ~ R . Powerful jets with Q jet ~ L bol (bolometric luminosity) can form via the large-scale magnetic fields created by dynamo processes in the disk corona of some AGNs. The maximal jet power extractable from the corona, Q ≤ 0.6 L c ( L c is the corona luminosity), is expected in this jet-formation scenario. The statistical results for the sample of AGNs are consistent with the predictions of this scenario. Finally, the possibility that the jet is driven from a super-Keplerian rotating hot layer located between the corona and the cold disk is discussed. We find that, in principle, this layer could also produce a powerful jet with Q jet ~ L bol .