Volume 560, December 2013
|Number of page(s)||16|
|Section||Catalogs and data|
|Published online||29 November 2013|
Exploring the bulk of the BL Lacertae object population
I. Parsec-scale radio structures⋆
1 INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
2 Dipartimento di Fisica e Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
3 Max Planck Institute for Radioastronomy, Auf dem Hügel 69, 53121 Bonn, Germany
4 INAF-Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
5 Università degli Studi dell’Insubria, via Valleggio 11, 22100 Como, Italy
6 Department of Physics and Astronomy, University of New Mexico, Albuquerque NM 87131, USA
7 Instituto de Astrofisica de Andalucia, CSIC, Apartado 3004, 18080 Granada, Spain
8 Universität Würzburg¨, Lehrstuhl für Astronomie, Emil-Fischer-Str. 31, 97074 Würzburg, Germany
9 Dipartimento di Fisica, Università degli Studi di Perugia, 06123 Perugia, Italy
Received: 25 June 2013
Accepted: 11 September 2013
Context. The advent of Fermi is changing our understanding on the radio and γ-ray emission in active galactic nuclei. Unlike pre-Fermi ideas, BL Lac objects are found to be the most abundant emitters in the γ-ray band. However, since they are relatively weak radio sources, most of their parsec-scale structure and their multifrequency properties are poorly understood and/or have not been investigated in a systematic fashion.
Aims. Our main goal is to analyze the radio and γ-ray emission properties of a sample of 42 BL Lacs selected, for the first time in the literature, with no constraint on their radio and γ-ray emission.
Methods. Thanks to new Very Long Baseline Array observations at 8 and 15 GHz for the whole sample, we present fundamental parameters here such as radio flux densities, spectral index information, and parsec-scale structure. Moreover, we search for γ-ray counterparts using data reported in the Second Catalog of Fermi Gamma-ray sources.
Results. Parsec-scale radio emission is observed in the majority of the sources at both frequencies. Gamma-ray counterparts are found for 14/42 sources.
Conclusions. The comparison between our results in radio and gamma-ray bands points out the presence of a large number of faint BL Lacs showing “non-classical” properties such as low source compactness, core dominance, no gamma-ray emission, and steep radio spectral indexes. A deeper multiwavelength analysis will be needed.
Key words: radio continuum: galaxies / galaxies: active / galaxies: jets
The calibrated uv and FITS files are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/560/A23
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.