1997A&A...326..501A

This paper presents the Lyα1215Å image, the velocity and velocity dispersion maps of the radiogalaxy 4C 41.17 (z=3.8), obtained with the integral field spectrograph TIGER at CFHT. In a relatively short exposure time (1.86h), the Lyα image reveals a bended elongated component surrounding a narrow bright peak and a West fainter component distributed along the radio axis. Roughly perpendicular to that main axis, a South-East to North-West faint extension to the central region is visible. A high density of smaller ionised clouds shows up in the vicinity of the radiogalaxy. The radial velocity and the velocity dispersion are mapped with a 0.61" spatial sampling. Radial velocities, from 0 to 700km/s, are essentially negative relative to the narrow peak, while velocity dispersions vary from 800km/s in the inner part up to 2000km/s at possible bow shock locations as well as in the South extension. Such data are essential to disentangle the various components of these distant sources. The kinematics, roughly similar to that of nearby galaxies, is interpreted by luminous clouds and a dusty disk structure. Measured negative velocities could be used as expansion rate constraints for hydrodynamics models of the radio jet propagation. They may also be due to an overestimate of the systemic velocity, in the hypothesis of a collapsing bright knot at the central bright peak. Information on star formation triggering along the radiojet will be derived from deeper observations.