Kinematics and morphology of ionized gas in Hickson Compact Group 18
Abstract
We present new observations of Hα emission in the Hickson Compact Group 18 (HCG 18) obtained with a scanning Fabry-Perot interferometer. The velocity field does not show motions of individual group members but, instead, a complex common velocity field for the whole group. The gas distribution is very asymmetric with clumps of maximum intensity coinciding with the optically brightest knots. Comparing Hα and HI data we conclude that HCG 18 is not a compact group but instead a large irregular galaxy with several clumps of star formation.
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