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Multifrequency spectral analysis of extragalactic radio sources in the 33-GHz VSA catalogue: sources with flattening and upturn spectrum

Tucci, M. and Rubiño-Martin, J. A. and Rebolo, R. and Genova-Santos, R. and Watson, R. A. and Battye, R. A. and Cleary, K. A. and Davies, R. D. and Davis, R. J. and Grainge, K. and Hobson, M. and Saunders, R. D. E. and Scaife, A. and Scott, P. F. (2008) Multifrequency spectral analysis of extragalactic radio sources in the 33-GHz VSA catalogue: sources with flattening and upturn spectrum. Monthly Notices of the Royal Astronomical Society, 386 (3). pp. 1729-1738. ISSN 0035-8711. doi:10.1111/j.1365-2966.2008.13161.x.

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We present an analysis of the spectral properties of the extragalactic radio sources in the nearly complete Very Small Array (VSA) sample at 33 GHz. Data from different surveys are used to study source spectra between 1.4 and 33 GHz. We find that, in general, spectra cannot be well described by a single power law in the range of frequencies considered. In particular, most of the VSA sources that are steep between 1.4 and 5 GHz, show a spectral flattening at ν > 5 GHz. We identify 20 objects (19 per cent of the sample) clearly characterized by an upturn spectrum, i.e. a spectrum falling at low frequencies (ν less than or similar to 5 GHz) and inverted at higher frequencies. Spectra with high-frequency flattening or upturn shape are supposed to occur when the emission from the active galactic nucleus (AGN) compact core begins to dominate over the component from extended lobes. This picture fits well with the AGN unified scheme, for objects observed at intermediate viewing angles of the AGN jet. Finally, we discuss implications that this class of sources can have on future cosmic microwave background observations at high resolution.

Item Type:Article
Related URLs:
URLURL TypeDescription
Rebolo, R.0000-0003-3767-7085
Genova-Santos, R.0000-0001-5479-0034
Additional Information:©2008 The Authors. Journal compilation ©2008 RAS. Accepted 2008 February 25. Received 2008 February 19; in original form 2007 July 12. MT thanks to Luigi Toffolatti for the careful reading of the manuscript and helpful comments and Elizabeth Waldram for the useful discussions.
Subject Keywords:galaxies: active; quasars: general; cosmic microwave background; radio continuum; galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20090423-203241922
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14061
Deposited By: Joy Painter
Deposited On:08 Jul 2009 17:01
Last Modified:08 Nov 2021 22:42

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