期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 451, 期 1, 页码 517-526出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stv988
关键词
galaxies: active; galaxies: jets; galaxies: nuclei; radio continuum: galaxies; X-rays: galaxies
资金
- I-CORE program of the Planning and Budgeting Committee
- Israel Science Foundation [1937/12, 1163/10]
- Israel's Ministry of Science and Technology
- Technion from the Lady Davis Foundation
- National Science Foundation [PHYS-1066293]
- Commonwealth of Australia
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1139950, 1140063] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1140019, 1139998, 1140031] Funding Source: National Science Foundation
The physical origin of radio emission in radio-quiet active galactic nuclei (RQ AGN) remains unclear, whether it is a downscaled version of the relativistic jets typical of radio-loud (RL) AGN, or whether it originates from the accretion disc. The correlation between 5 GHz and X-ray luminosities of RQ AGN, which follows LR = 10(-5) L-X observed also in stellar coronae, suggests an association of both X-ray and radio sources with the accretion disc corona. Observing RQ AGN at higher (mm-wave) frequencies, where synchrotron self-absorption is diminished, and smaller regions can be probed, is key to exploring this association. Eight RQ AGN, selected based on their high X-ray brightness and variability, were observed at 95 GHz with the CARMA (Combined Array for Research in Millimetre-wave Astronomy) and ATCA (the Australia Telescope Compact Array) telescopes. All targets were detected at the 1-10 mJy level. Emission excess at 95 GHz of up to x7 is found with respect to archival low-frequency steep spectra, suggesting a compact, optically thick core superimposed on the more extended structures that dominate at low frequencies. Though unresolved, the 95 GHz fluxes imply optically thick source sizes of 10(-4)-10(-3) pc, or similar to 10-1000 gravitational radii. The present sources lie tightly along an L-R (95 GHz) = 10(-4)L(X) (2-10 keV) correlation, analogous to that of stellar coronae and RQ AGN at 5 GHz, while RL AGN are shown to have higher L-R/L-X ratios. The present observations argue that simultaneous mm-wave and X-ray monitoring of RQ AGN features a promising method for understanding accretion disc coronal emission.
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