Long-slit and Fabry-Perot spectroscopy of collisional ring galaxy Arp 10
  We present results of Fabry-Perot and long-slit spectroscopy of the peculiar galaxy Arp 10. The ionized gas velocity field shows evidence for significant radial motions in both outer and inner galactic rings. Long-slit spectroscopy reveals gradients of age and metallicity of stellar population in agreement with the propagating nature of star formation in the galaxy. We present strong evidence that a small ``knot'' at 5 arcsec from the center of Arp 10 is its dwarf elliptic satellite, the most probable ``intruder'' responsible for triggering the expanding rings in Arp 10. 
A. V. Moiseev (1), D. V. Bizyaev (2,3), E. I. Vorobyov (4,5) ((1) SAO   RAS Russia, (2) Univ. of Texas El Paso (3) SAI Russi...