Letters to the Editor
Global e-VLBI observations of the gamma-ray narrow line Seyfert 1 PMN J0948+0022
INAF Istituto di Radioastronomia, via Gobetti 101,
2 Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands
3 MTA Research Group for Physical Geodesy and Geodynamics, PO Box 91, 1521 Budapest, Hungary
4 ICRAR/Curtin Institute of Radio Astronomy, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
5 Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
6 INAF Osservatorio Astronomico di Brera, 23807 Merate, Italy
7 FOMI Satellite Geodetic Observatory, Budapest, PO Box 585, 1592 Hungary
8 Department of Physics, University of Tasmania, Hobart Tasmania 7001, Australia
9 Observatorio Astronómico Nacional, 28014 Madrid, Spain
10 Shanghai Astronomical Observatory, Shanghai 200030, PR China
11 Dr. Remeis Sternwarte & ECAP, Universität Erlangen-Nürnberg, Sternwartstrasse 7, 96049 Bamberg, Germany
12 Center for Research and Exploration in Space Science and Technology, NASA GSFC, Greenbelt, MD 20771, USA
13 Universities Space Research Association, Columbia, MD 21044, USA
14 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
15 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands
16 CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW 1710, Australia
17 NIICT, Kashima Space Research Center, 893-1, Hirai, Kashima, Ibaraki, 314, Japan
Received: 3 February 2011
Accepted: 14 February 2011
Context. There is growing evidence of relativistic jets in radio-loud narrow-line Seyfert 1 (RL-NLS1) galaxies.
Aims. We constrain the observational properties of the radio emission in the first RL-NLS1 galaxy ever detected in gamma-rays, PMN J0948+0022, i.e., its flux density and structure in both total intensity and polarization, its compactness, and variability.
Methods. We performed three real-time e-VLBI observations of PMN J0948+0022 at 22 GHz, using a global array including telescopes in Europe, East Asia, and Australia. These are the first e-VLBI science observations ever carried out with a global array, reaching a maximum baseline length of 12 458 km. The observations were part of a large multiwavelength campaign in 2009.
Results. The source is detected at all three epochs. The structure is dominated by a bright component, more compact than 55 μas, with a fainter component at a position angle θ ~ 35°. Relativistic beaming is required by the observed brightness temperature of 3.4 × 1011 K. Polarization is detected at a level of about 1%.
Conclusions. The parameters derived by the VLBI observations, in addition to the broad-band properties, confirm that PMN J0948+0022 is similar to flat spectrum radio quasars. Global e-VLBI is a reliable and promising technique for future studies.
Key words: galaxies: active / galaxies: Seyfert / galaxies: jets / instrumentation: high angular resolution / instrumentation: interferometers
© ESO, 2011