NUclei of GAlaxies^*

V. Radio emission in 7 NUGA sources

¹ Universität zu Köln, I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany e-mail: [krips;eckart]@ph1.uni-koeln.de
² Harvard-Smithsonian Center for Astrophysics, SMA project, 645 North A'Ohoku Place, Hilo, HI 96720, USA e-mail: mkrips@cfa.harvard.edu
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: tkrichbaum@mpifr-bonn.mpg.de
⁴ ESO, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany e-mail: jpott@eso.org
⁵ Instituto de Astrofísica de Andalucía (CSIC), C/ Camino Bajo de Huétor 24, Apartado 3004, 18080 Granada, Spain
⁶ IRAM, Avenida Divina Pastora 7, Núcleo Central, 18012 Granada, Spain e-mail: leon@iram.es
⁷ Institut de Radio-Astronomie Millimétrique (IRAM), 300 rue de la Piscine, 38406 Saint-Martin-d'Hères, France e-mail: neri@iram.fr
⁸ Observatorio Astronómico Nacional (OAN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain e-mail: s.gburillo@oan.es
⁹ Observatoire de Paris, LERMA, 61 Av. de l'Observatoire, 75014 Paris, France e-mail: francoise.combes@obspm.fr; fboone@mpifr-bonn.mpg.de
¹⁰ Department of Physics and Astronomy, Rutgers, the State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019, USA e-mail: ajbaker@physics.rutgers.edu
¹¹ Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany e-mail: linda@mpe.mpg.de
¹² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: schinner@mpia.de
¹³ INAF-Istituto di Radioastronomia/Sezione Firenze, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: hunt@arcetri.astro.it

Received: 17 February 2006
Accepted: 21 December 2006

Abstract

We present high angular resolution radio snap-shot observations of seven nearby low-luminosity active galaxies (LLAGN) from the NUclei of GAlaxies (NUGA) survey. The observations were conducted with MERLIN and EVN/VLBI at 18 cm and 6 cm. At all observed angular resolutions and frequencies, we find indications for extended emission in about ~40% of the sources, consistent with the decrease of flux with increasing angular resolution. The extended components resemble jet emission in a majority of cases, consistent with the optically thin synchrotron emission implied by their steep spectra. We consider the compact 6 cm EVN/VLBI radio emission of our sources in the context of the “fundamental plane” that previous LLAGN studies identified within the three-dimensional parameter space of radio luminosity, X-ray luminosity, and black hole mass. We demonstrate, using NGC 7217 and NGC 1068 as particular examples, that high-resolution, multi-epoch radio observations offer useful information about the origin of offsets from the fundamental plane.