Letters to the Editor

Global e-VLBI observations of the gamma-ray narrow line Seyfert 1 PMN J0948+0022

¹ INAF Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
e-mail: giroletti@ira.inaf.it
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

Abstract

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.