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Published January 1, 2011 | Published
Journal Article Open

Characteristics of Gamma-ray Loud Blazars in the VLBA Imaging and Polarimetry Survey


The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong γ-ray emission. At lower flux levels, radio flux density does not directly correlate with γ-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the γ-ray loud and quiet FSRQs can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the γ-ray loud FSRQs are fundamentally different from the γ-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for γ-ray loud AGNs.

Additional Information

© 2011 The American Astronomical Society. Received 2010 August 4; accepted 2010 October 27; published 2010 December 9. We thank Matt Lister and Ann Wehrle for useful discussions. We also thank Teddy Cheung, Marcello Giroletti, Yuri Kovalev, Frank Schinzel, David Thompson, and Steve Tremblay for their helpful comments. Also, we express our appreciation to the anonymous referee for their insightful and helpful criticism. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The NASA/IPAC Extragalactic Database (NED) is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. We thank NASA for support under FERMI grant GSFC 21078/ FERMI08-0051.

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