| Research Abstract |
Galaxies have been classified into two basic categories, elliptical Galaxies and disk galaxies. The latter type of galaxies are supported by rotational motion of constituent stars, while the former type by their random motion. The disk Galaxies consist of a cental bulge and a rotational thin disk. However, no clear understanding is given for their formation mechanisms and which system was firstly formed from proto galaxy clouds.
Polar ring galaxies are identified as peculiar galaxies with a rotating disk with rotation axis prthogonal to that of the main disk, where the second disk are believed to be form from infalling gas from colliding partner galaxies. These peculiar galaxies may be a nice targets to study formation process of disks during formation process of disk galaxies in the early universe.
We have tried to observe several polar ring galaxies at Okayama Astrophysical Observatory. Due to poor wheather condition, no scientific results have been obtained. However, we obtained nice spectra of a bright Sa (r! ) galaxy NGC 7742, which has a bright prominent nuclear ring. By using HST archival data on this galaxy, we found the disk of the galaxy shows only a few percent deviation from circular symmetry on its surface photometry. Nuclear ring could be formed due to Lindblad resonance of the disk with a small amound of oval asymmmetry.
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