NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-25 T21:57:23 PDT
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For refcode 2013MNRAS.432.1138P:
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NED Abstract

Copyright by Royal Astronomical Society. 2013MNRAS.432.1138P Sub-parsec radio cores in nearby Seyfert galaxies Panessa, Francesca; Giroletti, Marcello Abstract. We present a census of sub-pc scale properties of the very long baseline interferometry (VLBI) cores in a complete sample of local Seyfert galaxies. Out of 23 sources with a Very Large Array (VLA) detection, 17 are detected also with VLBI at 1.7 GHz and/or 5 GHz, with an average monochromatic radio luminosity log[P_5 GHz_/W Hz^-1^] = 19.4. Radio cores are of heterogeneous nature, the majority of them showing elongated structures or accompanied by extra components, broad ranges of brightness temperatures (10^5^-10^10^ K) and spectral indices (from steep to highly inverted). Interestingly, the detection rate (26 per cent) of water maser emission is considerably higher than that found in previous surveys (~10 per cent), suggesting that distance biases could significantly affect our knowledge of the actual occurrence of this phenomenon. The VLBI observational properties of type 1 and type 2 nuclei are similar except for the T_B_, which is on average higher in type 1. These results suggest that both thermal and non-thermal emission are common in low-luminosity active galactic nuclei, with a prevalence of free-free processes among type 2 cores, likely associated with molecular gas. Though limited by the low-number statistics, we find no significant correlation between the VLBI radio luminosity and the nuclear X-ray luminosity; the latter appears to be more connected to the tens of pc scale VLA radio emission, rather than to the sub-pc scales, particularly in the most X-ray luminous sources. The X-ray radio loudness parameter R_X_ = L (6 cm)/L(2-10 keV) is on average very low (<log R_X_> = -4.8), with comparatively higher R_X_ found for sources with the largest black hole masses and the lowest Eddington ratios, although the radio power does not appear to depend on the accretion rate. Key words: galaxies: active, galaxies: jets, galaxies: nuclei, galaxies: Seyfert, radio continuum: galaxies, X-rays: galaxies
Retrieve 28 NED objects in this reference.
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