SUBMILLIMETER INTERFEROMETRY OF THE LUMINOUS INFRARED GALAXY NGC 4418: A HIDDEN HOT NUCLEUS WITH AN INFLOW AND AN OUTFLOW

Journal Article · Sun Feb 10 00:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/764/1/42· OSTI ID:22167814

Sakamoto, Kazushi; Ohyama, Youichi ^[1]; Aalto, Susanne; Costagliola, Francesco ^[2]; Martin, Sergio ^[3]; Wiedner, Martina C. ^[4]; Wilner, David J. ^[5]

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1. Academia Sinica, Institute of Astronomy and Astrophysics, Taiwan (China)
2. Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala (Sweden)
3. European Southern Observatory, Santiago (Chile)
4. LERMA and UMR 8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, F-75014 Paris (France)
5. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

We have observed the nucleus of the nearby luminous infrared galaxy NGC 4418 with subarcsec resolution at 860 and 450 {mu}m for the first time to characterize its hidden power source. A {approx}20 pc (0.''1) hot dusty core was found inside a 100 pc scale concentration of molecular gas at the galactic center. The 860 {mu}m continuum core has a deconvolved (peak) brightness temperature of 120-210 K. The CO(3-2) peak brightness temperature there is as high as 90 K at 50 pc resolution. The core has a bolometric luminosity of about 10{sup 11} L {sub Sun }, which accounts for most of the galaxy luminosity. It is Compton thick (N {sub H} {approx}> 10{sup 25} cm{sup -2}) and has a high luminosity-to-mass ratio (L/M) {approx} 500 L {sub Sun} M {sub Sun} {sup -1} as well as a high luminosity surface density 10{sup 8.5{+-}0.5} L {sub Sun} pc{sup -2}. These parameters are consistent with an active galactic nucleus to be the main luminosity source (with an Eddington ratio about 0.3), while they can be also due to a young starburst near its maximum L/M. We also found an optical color (reddening) feature that we attribute to an outflow cone emanating from the nucleus. The hidden hot nucleus thus shows evidence of both an inflow, previously seen with absorption lines, and the new outflow reported here in a different direction. The nucleus must be rapidly evolving with these gas flows.

• OSTI ID: 22167814
• Journal Information: Astrophysical Journal, Vol. 764, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
BOLOMETERS
BRIGHTNESS
CARBON MONOXIDE
COLOR MODEL
DENSITY
GALAXIES
GAS FLOW
HOT NUCLEI
INTERFEROMETRY
LUMINOSITY