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D.A. Russell (STScI/Jodrell Bank Observatory,University of Manchester), C.P. O'Dea, S.A. Baum (STScI), J.P. Leahy (Jodrell Bank Observatory,University of Manchester)
We present new HST/STIS images of the jet in 3C273 along with a new radio map produced from previously published VLA data. This is the first in a series of studies of a sample of extra-galactic jets. We find 3C273's jet is significantly wider in the radio, although the first knot has the same width at both frequencies. We also find the bright optical knots to be narrower than the general jet emission. The radio emission is observed to extend beyond the visible optical emission to a peak with no visible optical counterpart. Spectral index calculations using these and previous HST (Jester et al. 2001) observations clearly show the optical spectral index steepens smoothly along the jet from -0.9 at the first knot to around -1.6 at the end of the optical jet. Although no relation between the local brightness and the spectral index of the jet is observed. Chandra data (Marshall et al. 2001) has shown there must be a break in the spectrum in the near-UV and evidence of the near-UV break is found for a number of knots using the STIS near-UV MAMA detector. These results suggest that (1) in 3C273 the knots are not sites of significant particle re-acceleration, (2) we are seeing the effects of radiative losses on the relativistic electrons, (3) the higher energy particles are concentrated near the center of the jet, possibly in a region of lower magnetic field.
Financial support for this work was provided by NASA/STScI.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.