Radio Properties of Low Redshift Broad Line Active Galactic Nuclei
| Autor: | D. Michael Crenshaw, Paul J. Wiita, Stephen E. Rafter |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2008 |
| Předmět: |
Physics
education.field_of_study Solar mass Active galactic nucleus media_common.quotation_subject Astrophysics::High Energy Astrophysical Phenomena Astrophysics (astro-ph) Population FOS: Physical sciences Astronomy and Astrophysics Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Universe Redshift Black hole Space and Planetary Science education Order of magnitude Astrophysics::Galaxy Astrophysics media_common Line (formation) |
| Popis: | The question as to whether the distribution of radio-loudness in active galactic nuclei (AGN) is actually bimodal has been discussed extensively in the literature. Futhermore, there have been claims that radio-loudness depends on black hole mass and Eddington ratio. We investigate these claims using the low redshift broad line AGN sample of Greene & Ho (2007), which consists of 8434 objects at z < 0.35 from the Sloan Digital Sky Survey Fourth Data Release (SDSS DR4). We obtained radio fluxes from the Very Large Array Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey for the SDSS AGN. Out of the 8434 SDSS AGN, 821 have corresponding observed radio fluxes in the FIRST survey. We calculated the radio-loudness parameter (R) for all objects above the FIRST detection limit (1 mJy), and an upper limit to R for the undetected objects. Using these data, the question of radio bimodality is investigated for different subsets of the total sample. We find no clear demarcation between the radio-loud (RL, R > 10) and radio-quiet (RQ, R < 10) objects, but instead fill in a more radio-intermediate population in a continuous fashion for all subsamples. We find that 4.7% of the AGN in the flux-limited subsample are RL based on core radio emission alone. We calculate the radio-loud fraction (RLF) as both a function of black hole mass and Eddington ratio. The RLF decreases (from 13% to 2%) as Eddington ratio increases over 2.5 order of magnitude. The RLF is nearly constant (~5%) over 4 decades in black hole mass, except for an increase at masses greater than 10^8 solar masses. We find for the FIRST detected subsample that 367 of the RL AGN have black hole masses less than 10^8 solar masses, a large enough number to indicate that RL AGN are not a product of only the most massive black holes in the local universe. 28 pages, 14 figures, accepted to AJ |
| Databáze: | OpenAIRE |
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