A robust derivation of the tight relationship of radio core dominance to inclination angle in high redshift 3CRR sources

Journal Article · Thu Oct 20 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/830/2/82· OSTI ID:22868591

Marin, Frédéric ^[1]; Antonucci, Robert ^[2]

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1. Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, F-67000 Strasbourg (France)
2. Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States)

It is believed that, in radio-loud active galactic nuclei (AGNs), the core radio flux density can be normalized to the flux density of the extended lobe emission to infer the orientation of a radio source. However, very little is known about the reliability and precision of this method, and we are unaware of any robust conversion recipe to infer the inclination from the core dominance. Investigating whether or not the radio core dominance parameter R separates the quasars from the radio galaxies in the z ⩾ 1 3CRR catalog, we found excellent agreement of R with optical type, infrared flux ratios, and optical polarization. This indicates that probably both R and optical classification are very good orientation indicators, and the unified model is strongly predictive for these objects. The relative number densities indicate half-opening angles close to 60°, as expected from large surveys. The separations of optical types according to radio core dominance as well as near-infrared/MIR ratios, which are essentially perfect, mean that there can be only a small dispersion of torus half-opening angles. Also, even though torus dust is thought to be clumpy, there is an almost zero probability to see a type-1 source at high inclination. Finally, using only the Copernican Principle, i.e., the assumption that solid angle is filled uniformly with source axis orientations, we estimated a semi-empirical relation between core dominance and AGN inclination. This makes it possible to use R to infer the inclination of a source to an accuracy of ∼10° or less, at least for this type of object.

• OSTI ID: 22868591
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 830; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CATALOGS
CLASSIFICATION
COSMIC DUST
DENSITY
DISPERSIONS
EMISSION
FLUX DENSITY
GALAXY NUCLEI
INCLINATION
ORIENTATION
POLARIZATION
QUASARS
RADIO GALAXIES
RED SHIFT
RELIABILITY
UNIFIED MODEL