A Multi-Wavelength Study of the High Surface Brightness Hotspot in PKS1421-490 - Astrophysics > High Energy Astrophysical PhenomenaReportar como inadecuado




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Abstract: Long Baseline Array imaging of the z=0.663 broad line radio galaxyPKS1421-490 reveals a 400 pc diameter high surface brightness hotspot at aprojected distance of approximately 40kpc from the active galactic nucleus. Theisotropic X-ray luminosity of the hotspot, L {2-10 keV} = 3 10^{44} ergs-s, iscomparable to the isotropic X-ray luminosity of the entire X-ray jet ofPKS0637-752, and the peak radio surface brightness is hundreds of times greaterthan that of the brightest hotspot in Cygnus A. We model the radio to X-rayspectral energy distribution using a one-zone synchrotron self Compton modelwith a near equipartition magnetic field strength of 3 mG. There is a strongbrightness asymmetry between the approaching and receding hotspots and the hotspot spectrum remains flat alpha ~ 0.5 well beyond the predicted coolingbreak for a 3 mG magnetic field, indicating that the hotspot emission may beDoppler beamed. A high plasma velocity beyond the terminal jet shock could bethe result of a dynamically important magnetic field in the jet. There is achange in the slope of the hotspot radio spectrum at GHz frequencies fromalpha~0.5 to alpha<0.2, which we model by incorporating a cut-off in theelectron energy distribution at gamma {min} ~ 650, with higher values impliedif the hotspot emission is Doppler beamed. We show that a sharp decrease in theelectron number density below a Lorentz factor of 650 would arise from thedissipation of bulk kinetic energy in an electron-proton jet with a Lorentzfactor Gamma {jet} ~ 5.



Autor: L. E. H. Godfrey 1, 2, G. V. Bicknell 1, J. E. J. Lovell 2,3,4, D. L. Jauncey 2, J. Gelbord 5, D. A. Schwartz 6, H. L. Marshall 7

Fuente: https://arxiv.org/







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