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CO emission from the nucleus of infrared galaxy NGC 4418 - an early AGM phase?

1990; IOP Publishing; Volume: 365; Linguagem: Inglês

10.1086/185874

1538-4357

Kimiaki Kawara, Yoshiaki Taniguchi, Naomasa Nakai, Yoshiaki Sofue,

Spectroscopy and Laser Applications

view Abstract Citations (16) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CO Emission from the Nucleus of Infrared Galaxy NGC 4418: an Early AGN Phase? Kawara, Kimiaki ; Taniguchi, Yoshiaki ; Nakai, Naomasa ; Sofue, Yoshiaki Abstract The ^12^CO (J=1-0) emission has been detected in an extremely extinguished galaxy NGC 4418. The inferred mass of molecular gas is 4 x 10^8^ M_sun_ in the central 15 arcsec region of the galaxy. Combining the narrow CO line width (85 km s^-1^) with the extinction value derived from the 10 micron silicate absorption, it is suggested that the molecular gas clouds are highly concentrated toward the center or dynamically decoupled from the underlying stellar system, rotating more slowly than the stars and falling to the center. We hypothesize that NGC 4418 is at the very early phase of its AGN activity, and that the radiation from the nucleus is efficiently absorbed by dense ambient gas and reemitted in the far-infrared, taking the following peculiar properties into account: (1) the 1.5 GHz map recently reported by Condon et al. that measured 38.5 mJy in a 0.5" x 0.3" core brightness temperature of 150,000 K), (2) no emission lines in the optical and near-infrared, (3) the ratio of the 1.5 GHz flux relative to the IRAS flux which is 10 times smaller than those of other IRAS galaxies, and (4) the ratio (=170) of the IR luminosity to the molecular gas mass which is 10 times greater than those of other galaxies with the comparable IR luminosity (L = 7 x 10^10^ L_sun_) and comparable to that of an ultraluminous IRAS galaxy Mrk 231 (Seyfert 1/QSO with L = 2 x 10^12^ L_sun_). Publication: The Astrophysical Journal Pub Date: December 1990 DOI: 10.1086/185874 Bibcode: 1990ApJ...365L...1K Keywords: Active Galactic Nuclei; Carbon Monoxide; Emission Spectra; Infrared Sources (Astronomy); Far Infrared Radiation; Interstellar Matter; Molecular Clouds; Seyfert Galaxies; Starburst Galaxies; Astrophysics; GALAXIES: INTERSTELLAR MATTER; GALAXIES: NUCLEI; GALAXIES: SEYFERT; RADIO SOURCES: GALAXIES full text sources ADS | data products SIMBAD (4) NED (1)