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Are spiral nuclei “active” in the radio continuum?

Published online by Cambridge University Press:  04 August 2017

Paul T. P. Ho  and
Jean L. Turner
Paul T. P. Ho
Affiliation:
Harvard University
Jean L. Turner
Affiliation:
University of California, Berkeley

Abstract

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Using the VLA, we obtained matched-array continuum observations at 6 and 2 cm. An angular resolution of ~1″ and an rms sensitivity of ~0.05 mJy were achieved for a sample of 17 nearby spiral galaxies. Spectral-index maps derived for the nuclear regions reveal a mixture of thermal and nonthermal activity. The use of high angular resolution and high frequencies was the key to the success in detecting thermal activity. Conversion from thermal fluxes to total number of ionizing photons suggests that star formation is very active in some of these cores (inner 500 pc), with a rate typically 10 times greater than in our own nuclear region. A number of the nuclear regions appear to be dominated by extended nonthermal emission with a steep spectrum. Among these, some are closely associated with thermal emission and hence are consistent with supernova activity. However there are sources exhibiting aligned structures, suggesting possible connections with a central active nucleus. In any case, at our achieved sensitivity level 16 out of 17 galaxies were detected in the radio continuum.

Type
PART II: COMPOSITION, STRUCTURE AND KINEMATICS
Information
Symposium - International Astronomical Union , Volume 106: The Milky Way Galaxy , 1985 , pp. 377 - 378
Copyright
Copyright © Reidel 1985 

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