NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-04-26 T04:39:36 PDT
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For refcode 2000ApJ...542..186N:
Retrieve 48 NED objects in this reference.
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2000ApJ...542..186N Radio Sources in Low-Luminosity Active Galactic Nuclei. I. VLA Detections of Compact, Flat-Spectrum Cores Neil M. Nagar, Heino Falcke, Andrew S. Wilson, and Luis C. Ho Received 2000 February 18; accepted 2000 May 26 ABSTRACT We report a high-resolution (0.2"), 15 GHz survey of a sample of 48 low- luminosity active galactic nuclei with the Very Large Array.5 Compact radio emission has been detected above a flux density of 1.1 mJy in 57% (17 of 30) of low-ionization nuclear emission-line region (LINER) nuclei and low- luminosity Seyfert galaxies. The 2 cm radio power is significantly correlated with the emission-line ([O I] {lambda}6300) luminosity. Using radio fluxes at other frequencies from the literature, we find that at least 15 of the 18 detected radio cores have a flat to inverted spectrum ( {alpha} >= -0.3, S{nu} is proportional to {nu}^{alpha}^). While the present observations are consistent with the radio emission originating in star- forming regions (the brightness temperatures are >= 10^2.5-4.5^ K), higher resolution radio observations of 10 of the detected sources, reported in an accompanying paper, show that the cores are very compact (<~1 pc), of high brightness temperature (T_b_ >~ 10^8^ K), and probably synchrotron self- absorbed, ruling out a starburst origin. Thus, our results suggest that at least 50% of low-luminosity Seyfert galaxies and LINERs in the sample are accretion powered, with the radio emission presumably coming from jets or advection-dominated accretion flows. We have detected only 1 of 18 "transition" (i.e., LINER + H II) nuclei observed, indicating that their radio cores are significantly weaker than those of "pure" LINERs. Compact 2 cm radio cores are found in both type 1 (i.e., with broad H{alpha}) and type 2 (without broad H{alpha}) nuclei. There is weak evidence, limited in significance by small numbers, that low-luminosity active galactic nuclei with compact radio cores exhibit radio ejecta preferentially aligned along the rotation axis of the galaxy disk. If this result were confirmed by a larger sample, it would lend support to the idea that the misalignment of accretion disks with the galaxy stellar disk in more luminous Seyfert galaxies is a result of radiation-pressure-induced warping of their accretion disks. Subject headings: accretion, accretion disks-galaxies: active -galaxies: nuclei-galaxies: Seyfert-radio continuum: galaxies-surveys
Retrieve 48 NED objects in this reference.
Please click here for ADS abstract

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