Propagating Star Formation in the Collisional Ring Galaxy Arp 10

Propagating star formation in a collisional ring galaxy Arp10 is investigatedby a complex approach, which includes the broad- and narrow-band photometry,long- slit spectroscopy, and scanning Fabry-Perot spectroscopy. The ionized gasvelocity field obtained with best spatial resolution to date indicates a non-isotropic expansion of the outer ring with a maximum velocity 110km/s. Strongvertical and non-circular motions are also seen in the vicinity of the innerring. Our kinematic data suggest that Arp10 has a small inclination i=22\degrand high total (luminous plus dark matter) mass of about $10^{12} M_{\odot}$within a 50 kpc radius.The abundance of oxygen 12 + log(O/H) in both star-forming rings is about 8.6.The analysis of spectral indices provides anestimate on the propagation velocities of both rings and metallicity of thepre-collision stellar population.A small "knot" near the nucleus of Arp10,whichwas previously suspected as a possible candidate for collision, is nowunambiguously identified as the "intruder" of at least 1/4 of the total mass ofArp~10.We use a simplified two-dimensional hydrodynamic modeling of galaxycollisions to test a collisional origin of Arp10. We confirm that the sizes ofthe inner and outer rings, maximum expansion velocity of the outer ring, andradial profile of the gas circular velocity can be reproduced by a near-centralcollision with the intruder galaxy, which occurred approximately 85Myr ago. Weacknowledge that an apparent crescent- shaped distribution of H$\alpha$emission in the outer ring is caused by a star formation threshold in the gasdisk of Arp10.Comment: 17 pages, 17 figures, accepted by Ap