EDP Sciences
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Volume 431, Number 2, February IV 2005
Page(s) 477 - 502
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20047021

A&A 431, 477-502 (2005)
DOI: 10.1051/0004-6361:20047021

The radio-ultraviolet spectral energy distribution of the jet in 3C 273

S. Jester1, H.-J. Röser1, K. Meisenheimer1 and R. Perley2

1  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: jester@fnal.gov
2  National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA

(Received 6 January 2004 / Accepted 23 October 2004 )

We present deep VLA and HST observations of the large-scale jet in 3C 273 matched to 0 $\farcs$3 resolution. The observed spectra show a significant flattening in the infrared-ultraviolet wavelength range. The jet's emission cannot therefore be assumed to arise from a single electron population and requires the presence of an additional emission component. The observed smooth variations of the spectral indices along the jet imply that the physical conditions vary correspondingly smoothly. We determine the maximum particle energy for the optical jet using synchrotron spectral fits. The slow decline of the maximum energy along the jet implies particle reacceleration acting along the entire jet. In addition to the already established global anti-correlation between maximum particle energy and surface brightness, we find a weak positive correlation between small-scale variations in maximum particle energy and surface brightness. The origin of these conflicting global and local correlations is unclear, but they provide tight constraints for reacceleration models.

Key words: galaxies: jets -- galaxies: quasars: individual: 3C 273 -- radiation mechanisms: non-thermal -- acceleration of particles

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