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A. C. Sadun (University of Colorado at Denver), S. B. Fajardo-Acosta (University of Denver)
We obtained near-infrared images of the jet of the quasar 3C 273, in order to derive precise photometry of discrete components (knots) along the jet. The power-law spectral energy distribution (SED) of the knots is well known in the UV, optical, and radio wavelength regimes. However, the radio spectrum is a factor of about 5 higher than the extrapolation from the UV and optical SED. It is not known why this discontinuity occurs, or at what wavelength the spectral slope and flux level change. To address these questions, we obtained J and K images of the jet with the NSFCAM near-infrared array camera at the NASA IRTF, as part of a Service observation. The pixel size was 0.3 arcsec, and total integration times were 20 minutes at J and 28 minutes at K. Our images exhibit S/N greater than 10 in both filters. Thus these images allow us to study, for the first time, the morphology of the jet in the near-infrared. We look for evidence of a (J-K) color gradient along the jet, similar to the (B-R) gradient reported by Hayes & Sadun (1987, AJ, 94, 871). Also, our images show evidence that there may be an inner portion of the jet visible in the near-infrared within a couple of arcsecs from the quasar. Previous imaging at other wavelengths, including the visible, do not show the jet at distances less than 10 arcsec from the quasar.