The millimeter wave continuum spectrum of Centaurus A and its nucleus
Journal article, 2008

Aims. We study the radio emission mechanism of the FR-I AGN NGC 5128 (Centaurus A). Methods. We determine the centimeter and millimeter continuum spectrum of the whole Centaurus A radio source and measure at frequencies between 86 GHz (3.5 mm) and 345 GHz (0.85 mm) the continuum emission from the active radio galaxy nucleus at various times between 1989 and 2005. Results. The integral radio source spectrum becomes steeper at frequencies above 5 GHz, where the spectral index changes from alpha(low) = -0.70 to alpha(high) = -0.82. The SW outer lobe has a steeper spectrum than the NE middle and outer lobes (alpha = -1.0 vs. -0.6). Millimeter emission from the core of Centaurus A is variable, a variability that correlates appreciably better with the 20-200 keV X-ray variability than with 2-10 keV variability. Conclusions. In its quiescent state, the core has a spectral index alpha = -0.3, which steepens when the core brightens. The variability appears to be mostly associated with the inner nuclear jet components that have been detected in VLBI measurements. The densest nuclear components are optically thick below 45-80 GHz.

galaxies : nuclei

submillimeter

galaxies : active

radio continuum : galaxies

galaxies : peculiar

galaxies : individual : NGC 5128

Author

F.P. Israel

D. Raban

Roy Booth

Chalmers, Department of Radio and Space Science, National Facility for Radio Astronomy

F.T. Rantakyrö

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 483 3 741-748

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361

More information

Created

10/7/2017