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A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421-490


Godfrey, LEH and Bicknell, GV and Lovell, JEJ and Jauncey, DL and Gelbord, J and Schwartz, DA and Marshall, HL and Birkinshaw, M and Georganopoulos, M and Murphy, DW and Perlman, ES and Worrall, DM, A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421-490, The Astrophysical Journal, 695, (1) pp. 707-723. ISSN 0004-637X (2009) [Refereed Article]

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Copyright 2009 The American Astronomical Society

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DOI: doi:10.1088/0004-637X/695/1/707


Long Baseline Array imaging of the z=0.663 broad line radio galaxy PKS1421-490 reveals a 400 pc diameter high surface brightness hotspot at a projected distance of approximately 40kpc from the active galactic nucleus. The isotropic X-ray luminosity of the hotspot, L_{2-10 keV} = 3 10^{44} ergs/s, is comparable to the isotropic X-ray luminosity of the entire X-ray jet of PKS0637-752, and the peak radio surface brightness is hundreds of times greater than that of the brightest hotspot in Cygnus A. We model the radio to X-ray spectral energy distribution using a one-zone synchrotron self Compton model with a near equipartition magnetic field strength of 3 mG. There is a strong brightness asymmetry between the approaching and receding hotspots and the hot spot spectrum remains flat (alpha ~ 0.5) well beyond the predicted cooling break for a 3 mG magnetic field, indicating that the hotspot emission may be Doppler beamed. A high plasma velocity beyond the terminal jet shock could be the result of a dynamically important magnetic field in the jet. There is a change in the slope of the hotspot radio spectrum at GHz frequencies from alpha~0.5 to alpha<0.2, which we model by incorporating a cut-off in the electron energy distribution at gamma_{min} ~ 650, with higher values implied if the hotspot emission is Doppler beamed. We show that a sharp decrease in the electron number density below a Lorentz factor of 650 would arise from the dissipation of bulk kinetic energy in an electron/proton jet with a Lorentz factor Gamma_{jet} ~ 5.

Item Details

Item Type:Refereed Article
Keywords:galaxies:active-galaxies:jets-quasars:individual (PKS 1421-490)
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Lovell, JEJ (Dr Jim Lovell)
ID Code:57519
Year Published:2009
Web of Science® Times Cited:39
Deposited By:Physics
Deposited On:2009-07-23
Last Modified:2012-01-17

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