Hubble Space Telescope far-ultraviolet imaging of the jet in 3C 273: A common emission component from optical to X-rays

Abstract

ABSTRACT We present far-ultraviolet (far-UV) observations at ∼150 nm of the jet of quasar 3C 273 obtained with the Advanced Camera for Surveys (ACS) Solar Blind Channel onboard the Hubble Space Telescope. While the jet morphology is very similar to that in the optical and near-UV, the spectral energy distributions of the jet's subregions show an upturn in νfν at 150 nm compared to 300 nm everywhere in the jet. Moreover, the 150-nm flux is compatible with extrapolating the X-ray power law down to the UV region. This constitutes strong support for a common origin of the jet's far-UV and X-ray emission. It implies that even a substantial fraction of the visible light in the X-ray brightest parts of the jet arises from the same spectral component as the X-rays, as had been suggested earlier based on Spitzer Space Telescope observations. We argue that the identification of this UV/X-ray component opens up the possibility to establish the synchrotron origin of the X-ray emission by optical polarimetry. © 2007 The Authors. Journal compilation © 2007 RAS.