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Published March 21, 2006 | Published
Journal Article Open

5-GHz MERLIN and VLBA observations of compact 9C sources


In this paper, we present subarcsecond resolution observations of 36 compact sources from the 15ʰ region of the 15-GHz 9th Cambridge survey. These sources all have previously measured simultaneous continuum radio spectra spanning 1.4–43 GHz and we classify each source by fitting a quadratic function to its spectrum. Using the Multi-Element Radio-Linked Interferometer Network and the Very Long Baseline Array, both at 5 GHz, we resolve all six steep-spectrum objects and four of the 13 flat-spectrum objects. However, none of the 16 objects with convex spectra peaking above 2.5 GHz is resolved even at <3-mas resolution. These results, in combination with the findings of a 15-GHz variability study, suggest that emission from the high-frequency peaking objects is affected by relativistic beaming, and that these objects are not necessarily as young as the synchrotron self-absorption interpretation of their peak frequencies would imply.

Additional Information

© 2006 The Authors. Journal compilation © 2006 RAS. Accepted 2005 December 2. Received 2005 November 23; in original form 2005 September 29. We are grateful to Peter Thomasson and Tom Muxlow for help observing and calibrating the MERLIN data. This work has made use of the NED, which is operated by the Jet Propulsion Laboratory California Institute of Technology, under contract with the National Aeronautics and Space Administration. MERLIN is operated by the University of Manchester as a National Facility of the UK Particle Physics & Astronomy Research Council. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

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