Star formation in collisional ring galaxies and the circumnuclear regions of active galactic nuclei

This dissertation contains multiwavelength observational projects on collisional ring galaxies, active galactic nuclei (AGNs), and neutral hydrogen observations of the collisional ring galaxy Arp 118 (an interacting pair NGC 1144/1143);I have demonstrated in my dissertation research that: starburst knots of individual collisional ring galaxies cluster around the same, very young age suggesting that their formation was recently triggered by a coherent event all around the ring and strongly supports their production as a result of the passage of a radial density wave; the atomic and molecular emission in the strongly interacting galaxy Arp 118 appears to be very asymmetrically distributed such that the NW region of the galaxy is mainly atomic hydrogen, whereas the SE region has an interstellar medium which is ~94% molecular hydrogen. One possibility is that in the SE region there is a rapid conversion of HI to H2, which may be a result of the highly off-center collision between NGC 1144 and NGC 1143; and the global far-infrared colors of Seyfert galaxies may be linked to their radio morphologies