Journal Article

Parsec-scale morphology and spectral-index distribution in faint high-frequency peakers

M. Orienti and D. Dallacasa

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 424, issue 1, pages 532-544
Published in print July 2012 | ISSN: 0035-8711
Published online July 2012 | e-ISSN: 1365-2966 | DOI:
Parsec-scale morphology and spectral-index distribution in faint high-frequency peakers

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We investigate the parsec-scale structure of 17 high-frequency peaking radio sources from the faint high-frequency peaker sample. Very Long Baseline Array (VLBA) observations were carried out at two adjacent frequencies, 8.4 and 15.3 GHz, both in the optically thin part of the spectrum, to obtain the spectral-index information. We found that 64 per cent of the sources are resolved into subcomponents, while 36 per cent are unresolved even at the highest frequency. Among the resolved sources, seven have a morphology and a spectral-index distribution typical of young radio sources, while in other four sources, all optically associated with quasars, the radio properties resemble those of the blazar population. The equipartition magnetic field of the single components are a few tens milliGauss, similar to the values found in the hotspots of young sources with larger sizes. Such high magnetic fields cause severe radiative losses, precluding the formation of extended lobe structures emitted at centimetre wavelengths. The magnetic fields derived in the various components of individual source are usually very different, indicating a non-self-similar source evolution, at least during the very first stages of the source growth.

Keywords: radiation mechanisms: non-thermal; galaxies: active; radio continuum: general

Journal Article.  7963 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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