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Astron. Astrophys. 360, 99-106 (2000)

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2. The jet of 3C 273 at radio to optical wavelengths

As indicated in Fig. 1, the radio jet is detected all the way from the core out to the hot spot. The faint optical structure, however, although coinciding in position angle with the line joining radio components A (hot spot) and B (core), seems to be detectable only outwards of [FORMULA]". It also terminates about 1" before the peak in the radio hot spot is reached. At the quasar's redshift of 0.158 the projected length is [FORMULA]60 kpc 1. Greenstein & Schmidt (1964) in their detailed study of 3C 273 and 3C 48 briefly discuss also this jet. Their spectrum of its outer end exhibited a featureless blue continuum and they assumed the optical radiation is of the same origin as the radio emission, i.e. synchrotron radiation from relativistic particles. This was proven by Röser & Meisenheimer (1986, 1991) using optical polarimetry. Further hints about the synchrotron emission are provided by studies of the spatially resolved continua of individual knots in the jet. Meisenheimer & Heavens (1986) present a simple model describing the global shape of the continuum including an exponential cut-off observed in the hot spot at the jet's outer end reflecting the maximum energy gained by the relativistic particles. Applying this model to the other knots in the jet indicates that we also see distributions of relativistic particles truncated at some maximum energy, except for the innermost visible knot (Meisenheimer et al. 1996), which essentially has no cut-off at all. In view of these results the marginal detection of X-ray emission by Harris & Stern (1987) would naturally be associated with this innermost knot, although they place the centroid of the X-ray emission further out.

[FIGURE] Fig. 1. The quasar 3C 273 at radio (left) and optical (right) wavelengths. The main morphological features are indicated. The radio jet terminates in the bright radio hot spot at a distance of [FORMULA] from the core. The faint extensions visible to the north of both ends of the optical jet are not detected at radio wavelengths.

We have therefore used the ROSAT HRI with its better spatial resolution and sensitivity to verify the X-ray emission from this jet and to gain further insight into the emission mechanism.

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© European Southern Observatory (ESO) 2000

Online publication: July 27, 2000