Multi-frequency investigation of the parsec- and kilo-parsec-scale radio structures in high-redshift quasar PKS 1402+044

Free access article

Issue		A&A Volume 489, Number 2, October II 2008


Page(s)		517 - 524
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:200809846
Published online		23 July 2008

A&A 489, 517-524 (2008)
DOI: 10.1051/0004-6361:200809846

Multi-frequency investigation of the parsec- and kilo-parsec-scale radio structures in high-redshift quasar PKS 1402+044

J. Yang^{1, 2}, L.I. Gurvits³, A.P. Lobanov⁴, S. Frey^{5, 6}, and X.-Y. Hong¹

¹ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, 200030 Shanghai, PR China
    e-mail: junyang@shao.ac.cn
² Graduate University of the Chinese Academy of Sciences, Beijing, PR China
³ Joint Institute for VLBI in Europe, PO Box 2, 7990 AA Dwingeloo, The Netherlands
    e-mail: lgurvits@jive.nl
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: alobanov@mpifr-bonn.mpg.de
⁵ FÖMI Satellite Geodetic Observatory, PO Box 585, 1592 Budapest, Hungary
    e-mail: frey@sgo.fomi.hu
⁶ MTA Research Group for Physical Geodesy and Geodynamics, PO Box 91, 1521 Budapest, Hungary

Received 26 March 2008 / Accepted 16 June 2008

Abstract
Aims. We investigate the frequency-dependent radio properties of the jet of the luminous high-redshift (z=3.2) radio quasar PKS 1402+044 (J1405+0415) by means of radio interferometric observations.
Methods. The observational data were obtained with the VLBI Space Observatory Programme (VSOP) at 1.6 and 5 GHz, supplemented by other multi-frequency observations with the Very Long Baseline Array (VLBA; 2.3, 8.4, and 15 GHz) and the Very Large Array (VLA; 1.4, 5, 15, and 43 GHz). The observations span a period of 7 years.
Results. We find that the luminous high-redshift quasar PKS 1402+044 has a pronounced “core-jet” morphology from the parsec to the kilo-parsec scales. The jet shows a steeper spectral index and lower brightness temperature with increasing distance from the jet core. The variation of brightness temperature agrees well with the shock-in-jet model. Assuming that the jet is collimated by the ambient magnetic field, we estimate the mass of the central object as ~ $10^9~M_\odot$ . The upper limit of the jet proper motion of PKS 1402+044 is 0.03 mas yr^-1 (~3c) in the east-west direction.

Key words: galaxies: individual: PKS 1402+044 -- galaxies: active -- galaxies: quasars: general -- galaxies: jets -- radio continuum: galaxies

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