The millimeter wave continuum spectrum of Centaurus A and its nucleus

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.

NATURVETENSKAP Fysik Astronomi, astrofysik och kosmologi hsv//swe
NATURAL SCIENCES Physical Sciences Astronomy, Astrophysics and Cosmology hsv//eng
radio continuum : galaxies
galaxies : individual : NGC 5128
galaxies : nuclei
galaxies : peculiar
submillimeter
galaxies : active

Raban, D.Universiteit Leiden (UL),Leiden University (UL) (författare)
Booth, Roy,1938Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)roy (författare)
Rantakyrö, F.T.European Southern Observatory Santiago (författare)
Universiteit Leiden (UL)Chalmers tekniska högskola (creator_code:org_t)

Ingår i:Astronomy and Astrophysics: EDP Sciences483:3, s. 741-7480004-63611432-0746

Av författaren/redakt...: Israel, F.P.; Raban, D.; Booth, Roy, 1938; Rantakyrö, F.T.

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