Volume 538, February 2012
|Number of page(s)||4|
|Published online||31 January 2012|
The blazar-like radio structure of the TeV source IC 310
Lehrstuhl für Astronomie, Universität Würzburg, Campus Hubland
e-mail: firstname.lastname@example.org; email@example.com; firstname.lastname@example.org; email@example.com
2 Departament d’Astronomia i Astrofísica, Universitat de València, 46100 Burjassot, València, Spain
3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Received: 6 October 2011
Accepted: 23 December 2011
Context. The radio galaxy IC 310 in the Perseus cluster has recently been detected in the gamma-ray regime at GeV and TeV energies. The TeV emission shows time variability and an extraordinarily hard spectrum, even harder than the spectrum of the similar nearby gamma-ray emitting radio galaxy M 87.
Aims. High-resolution studies of the radio morphology help to constrain the geometry of the jet on sub-pc scales and to find out where the high-energy emission might come from.
Methods. We analyzed May 2011 VLBA data of IC 310 at a wavelength of 3.6 cm, revealing the parsec-scale radio structure of this source. We compared our findings with more information available from contemporary single-dish flux density measurements with the 100-m Effelsberg radio telescope.
Results. We have detected a one-sided core-jet structure with blazar-like, beamed radio emission oriented along the same position angle as the kiloparsec scale radio structure observed in the past by connected interferometers. Doppler-boosting favoritism is consistent with an angle of θ38° between the jet axis and the line-of-sight, i.e., very likely within the boundary dividing low-luminosity radio galaxies and BL Lac objects in unified schemes.
Conclusions. The stability of the jet orientation from parsec to kiloparsec scales in IC 310 argues against its classification as a head-tail radio galaxy; i.e., there is no indication of an interaction with the intracluster medium that would determine the direction of the tail. IC 310 seems to represent a low-luminosity FRI radio galaxy at a borderline angle to reveal its BL Lac-type central engine.
Key words: galaxies: active / techniques: interferometric / X-rays: galaxies / radio continuum: general / gamma rays: galaxies / galaxies: individual: IC 310
© ESO, 2012
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