Volume 517, July 2010
|Number of page(s)||5|
|Published online||10 August 2010|
Letter to the Editor
Hanny's Voorwerp *
Evidence of AGN activity and a nuclear starburst in the central regions of IC 2497
Joint Institute for VLBI in Europe (JIVE), Postbus 2, 7990 AA Dwingeloo, The Netherlands
2 Leiden Observatory, Leiden University, PO Box 9513, 2300RA Leiden, The Netherlands
3 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, Univ. Manchester, Alan Turing Building, Oxford Road, Manchester, M13 9PL, UK e-mail: firstname.lastname@example.org
4 Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands e-mail: email@example.com
5 Centre for Supercomputing, Swinburne Univ. of Technology, Mail number H39, PO Box 218, Hawthorn, Victoria 3122, Australia
6 Kapteyn Astronomical Institute, Univ. Groningen, Postbus 800, 9700 AV Groningen, The Netherlands
7 MTA Research Group for Physical Geodesy and Geodynamics, PO Box 91, 1521 Budapest, Hungary
8 Univ. Alabama, Dept. Physics & Astronomy, Box 870324, University of Alabama, Tuscaloosa, AL 35487-0324, USA
9 Univ. Yale, Dept. Physics, J.W. Gibbs Laboratory, 260 Whitney Avenue, Yale University, New Haven, CT 06511, USA
10 Einstein Fellow
Accepted: 17 June 2010
We present high- and intermediate resolution radio observations of the central region in the spiral galaxy IC 2497, performed using the European VLBI Network (EVN) at 18 cm, and the Multi-Element Radio Linked Interferometer Network (MERLIN) at 18 cm and 6 cm. We detect two compact radio sources, with brightness temperatures above 105 K, suggesting that they are related to AGN activity. We show that the total 18 cm radio emission from the galaxy is dominated neither by these compact sources nor large-scale emission, but extended emission confined within a sub-kpc central region. IC 2497 therefore appears as a typical luminous infrared galaxy that exhibits a nuclear starburst with a massive star formation rate (M > 5 ) of 12.4 /yr. These results are in line with the hypothesis that the ionisation nebula “Hanny's Voorwerp” at a distance of ~ 15–25 kpc from the galaxy is ionised by the radiation cone of the AGN.
Key words: galaxies: active / galaxies: ISM / galaxies: individual: IC 2497 / galaxies: star formation
Table 2 is only available in electronic form at http://www.aanda.org
© ESO, 2010
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