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Radio-faint BL Lac objects and their impact on the radio/gamma-ray connection

Giroletti, Marcello and Pavlidou, V. and Reimer, A. and Taylor, G. B. and Tosti, G. and Giovannini, G. and Casadio, C. and Liuzzo, E. and Tamburri, S. (2012) Radio-faint BL Lac objects and their impact on the radio/gamma-ray connection. Advances in Space Research, 49 (9). pp. 1320-1326. ISSN 0273-1177.

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Radio and gamma-ray emissions in Active Galactic Nuclei (AGNs) are both related to the presence of relativistic particles in jets. With the advent of the Fermi Large Area Telescope (LAT), and thanks to its large sensitivity up to several GeV, many observational results are changing our understanding of these phenomena. BL Lac objects, which made up only a fraction of the known extragalactic gamma-ray source population before Fermi, have now become the most abundant class. However, since they are relatively weak radio sources, most of them are poorly known as far as their parsec scale structure and multi-wavelength properties are concerned. For this reason, we have selected a complete sample of 42 low redshift BL Lacs (independently of their gamma-ray properties) to study with a multi-wavelength (radio, optical, X-ray, gamma-ray) approach. Here, we present results and images of sources in the sample (most of which have never been observed before), using new VLBA observations at 8 and 15 GHz. Beyond this sample of BL Lacs, the population of gamma-ray AGNs has also dramatically enlarged in the Fermi era, permitting us to discuss the presence of a correlation between radio and gamma-ray properties with improved statistical significance. We explore the radio-gamma relation with several hundreds sources and using both simultaneous and archival radio data, thus tackling the impact of time variability.

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Additional Information:© 2012 COSPAR. Published by Elsevier Ltd. Received 5 September 2011; received in revised form 23 January 2012; accepted 1 February 2012. Available online 15 February 2012. M. Giroletti acknowledges generous support from the 38th COSPAR Assembly organizing committee for his participation in the Scientific Event E11 “Time variability at high energies: a probe of AGN physics (including VLBI)”. The authors wish to thank Prof. Enrico Massaro for his contribution in the early stages of this project. The Fermi LAT Collaboration acknowledges support from a number of agencies and institutes for both development and the operation of the LAT as well as scientific data analysis. These include NASA and DOE in the United States, CEA/Irfu and IN2P3/CNRS in France, ASI and INFN in Italy, MEXT, KEK, and JAXA in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the National Space Board in Sweden. Additional support from INAF in Italy and CNES in France for science analysis during the operations phase is also gratefully acknowledged.
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Japan Aerospace Exploration Agency (JAXA)UNSPECIFIED
K. A. Wallenberg FoundationUNSPECIFIED
Swedish Research CouncilUNSPECIFIED
National Space Board in SwedenUNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Subject Keywords:Gamma rays: galaxies; Radio continuum: galaxies; Galaxies: active; Galaxies: jets; BL Lacertae objects: general; Quasars: general
Issue or Number:9
Record Number:CaltechAUTHORS:20120523-112807770
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Official Citation:Marcello Giroletti, V. Pavlidou, A. Reimer, G.B. Taylor, G. Tosti, G. Giovannini, C. Casadio, E. Liuzzo, S. Tamburri, Radio-faint BL Lac objects and their impact on the radio/gamma-ray connection, Advances in Space Research, Volume 49, Issue 9, 1 May 2012, Pages 1320-1326, ISSN 0273-1177, 10.1016/j.asr.2012.02.005. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31615
Deposited By: Ruth Sustaita
Deposited On:24 May 2012 15:15
Last Modified:03 Oct 2019 03:53

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