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Further evidence for synchrotron self‐absorption from the CORALZ sample of young radio‐loud AGN
Author(s) -
Vries N. de,
Snellen I.A.G.,
Schilizzi R.T.,
Mack K.H.
Publication year - 2009
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200811159
Subject(s) - astrophysics , physics , synchrotron , redshift , radio frequency , angular diameter , global positioning system , radio spectrum , active galactic nucleus , absorption (acoustics) , astronomy , galaxy , telecommunications , optics , computer science , stars
Young radio‐loud active galactic nuclei form an important tool to investigate the evolution of extragalactic radio sources. In this paper we present a summary of our recent work on the CORALZ sample of young radio sources at low redshift. We have found strong evidence that the radio spectral turnovers in GPS and CSS sources are caused by synchrotron selfabsorption (SSA): the CORALZ sources follow the well established relation between radio spectral peak frequency and largest angular size, but with significantly smaller sizes at any particular peak frequency, compared to more powerful and more distant GPS/CSS sources, as expected from SSA theory combined with simple self‐similar evolution models. Current models that invoke free‐free absorption (FFA) to explain the spectral turnovers in GPS and CSS sources can not easily explain the relatively small angular sizes found for the CORALZ sources. We therefore conclude that, although FFA may play a role in some sources, the radio spectral turnovers in GPS and CSS radio sources are generally caused by SSA (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)