Kinematics of M51-type interacting galaxies

We present a kinematic catalogue for 21 M51-type galaxies. It consists of radial velocity distributions observed with long slit spectroscopy along different position angles, for both the main and satellite components. We detect deviations from circular motion in most of the main galaxies of each pair, due to the gravitational perturbation produced by the satellite galaxy. However some systems do not show significant distortions in their radial velocity curves. We found some differences between the directions of the photometric and kinematic major axes in the main galaxies with a bar subsystem. The Tully-Fisher relation in the B-band and Ks-band for the present sample of M51-type systems is flatter when compared with isolated galaxies. Using the radial velocity data set, we built a synthetic normalized radial velocity distribution, as a reference for future modeling of these peculiar systems. The synthetic rotation curve, representing the typical rotation curve of the main galaxy in an M51-type pair, is near to solid body-like inside 4 kpc, and then is nearly flat within the radial range 5-15 kpc. The relative position angles between the main galaxy major axis and the companion location, as well as the velocity difference amplitude, indicate that the orbital motion of the satellite has a large projection on the main galaxy equatorial plane. In addition, the radial velocity differences between the two galaxies indicate that the satellite orbital motion is within the range of amplitudes of the main galaxy rotation curve and all the M51-type systems studied here except for one, are gravitationally bounded.

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