Kinematic study at the Hα line in the north-eastern region of the Galactic supernova remnant IC443.

The distance of the Galactic supernova remnant (SNR) IC443 (G189.1+3.0, 3C157) is uncertain. Results based on measurements in the optical range from 0.7 to 1.5 kpc, while the assumption that the SNR is associated with the HII region S249 implies a distance of 1.5-2 kpc. We present the kinematics of the north-eastern region of SNR IC443. The results were obtained using a scanning Fabry-Pérot interferometer at the Hα line. The kinematics derived from the Fabry-Pérot velocity cubes enabled us to obtain the kinematic distance to this nebula. We estimate that IC 443 is located about 1.9 kpc from the Sun. IC 443 shows a complex morphology consisting of three interconnected roughly spherical subshells that have substantially different radii and centroids. The geometry is fully constrained by the structural and kinematic data. Two of these subshells together define the usually assumed boundaries of IC443, while the third includes optical filaments that extend beyond the bright north-eastern rim. These filaments have been shown to have well-correlated non-thermal radio counterparts. We present the kinematic results of Hα Fabry-Pérot observations obtained with the PUMA equipment at the 2.1-m telescope of the Observatorio Astronömico Nacional at San Pedro Mártir, Baja California,México. These results enable us to distinguish between the SNR and the HII region S249, both of which are in the line of sight. We find that the HII region is located 0.6 kpc in front of the SNR. [ABSTRACT FROM AUTHOR]