Detection of a nuclear radio source in NGC 7331: A relatively 'radio-quiet' liner

Abstract

view Abstract Citations (22) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of a Nuclear Radio Source in NGC 7331: A Relatively ``Radio-quiet'' Liner Cowan, John J. ; Romanishin, W. ; Branch, David Abstract We have used the Very Large Array to observe the nearby spiral galaxy NGC 7331. The observations detected an unresolved radio source in the nucleus of this galaxy, with flux densities of 234+/-25 microJy and 121+/-16 microJy at 20 and 6 cm, respectively. This is equivalent (at the distance of this galaxy) to luminosities of approximately 3 and 4 times that of the Galactic center source Sgr A at 20 and 6 cm. The source in NGC 7331, with a radio spectral index (Snu_ is proportional to νalpha^) of α = -0.6 +/- 0.1, sits in a region of very low gas density, surrounded by a ring of radio emission. Optical spectra show that NGC 7331 has a weak LINER nucleus. We compare the radio and optical properties of this nucleus with other LINER nuclei detected in the radio, and find that NGC 7331 has an unusually low radio to Hα flux ratio. The combination of an unresolved radio source and a LINER nucleus spectrum suggests that this galaxy harbors a massive black hole. The radio observations of NGC 7331 did not detect emission from the historical supernova 1959D with a 3 σ upper limit of 75 microJy at 20 cm. Publication: The Astrophysical Journal Pub Date: December 1994 DOI: 10.1086/187652 Bibcode: 1994ApJ...436L.139C Keywords: Active Galactic Nuclei; Black Holes (Astronomy); Light (Visible Radiation); Optical Emission Spectroscopy; Radio Sources (Astronomy); Spiral Galaxies; Supernovae; Astronomical Coordinates; Radio Emission; Spectral Emission; Very Large Array (Vla); Wavelengths; Astrophysics full text sources ADS | data products SIMBAD (8) NED (1)