The ``sheath'' around the jet

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Total Intensity

The ``sheath'' around the jet

  Averaged transverse intensity profile
Figure 3: Averaged transverse intensity profile across the entire jet at 8.4 GHz with 1.3" (FWHM) resolution.

The total intensity profiles shown in Figures 2 and 3 illustrate that there is also excess emission   within three to five jet radii (4 to 8/h kpc) of the jet axis. This excess, or ``sheath'', is not simply a broad band around the jet that is fully filled with diffuse emission. As well as some diffuse emission, it contains bright ridges resembling the lobe filaments, and a relative absence of emission close to the jet.

 Jet and sheath intensities vs. distance
Figure 4:  Transverse-integrated intensity of the jet and of the ``sheath'' plotted against distance from the nucleus.

The transverse-integrated intensity of the sheath tends to increase with that of the jet (Figure 4). The sheath is first detected at about the same distance from the nucleus as the first jet knot, but brightens less abruptly than the jet. Its ridge-like substructure complicates quantifying its collimation, or how well it aligns with the jet; but integrating transverse profiles of total and polarized intensity along axes at 0°, ±10° and ±20° to the jet implies that sheath and jet are coaxial to 10°. We cannot exclude the possibility that the sheath is merely part of the filamentary structure   of the lobe that is superposed on the jet by chance. The connection between their intensities (Figure 4) suggests, however, that the sheath includes features that influence, or are influenced by, the passage of the jet. There is no evidence of a similar sheath around the counterjet.