Abstract
ABSTRACT (N II]λ 6583 line profiles across the disk of the nearby Seyfert galaxy NGC 4258. The spectral grid spans 5' and resolves velocity structure across the prominent "four-branched jet". We find that the jets have total ionized mass 1.5 X 106Msun_ and [N II] λ6583/Hot ratios consistent with shock excitation (1 in the SE jet). Velocity dispersions along the SE jet average 80 km s-1^, compared to 40 km s-1^ in the H II regions. This broadening arises from a striking spatio- kinematic helicity of at least two plasma streams that wind through the observed phase subspace. Gaussian decomposition shows that the internal velocity dispersion of each helix is 100 km s-1^ In the SE we observe three cycles of wavelength 560 pc and ~170 pc transverse amplitude. A ballistic interpretation of the braiding at radii within 1 kpc and tangential (interpreted as source orbital) velocities of 150 Km s-1^ yields a deprojected outflow velocity of 1200 km s-1^, compact binary source masses of O(107^) Msun_, and source separation O10 pc. However, the detailed kinematic structure shows that some of the motion is along the helices.
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