Neutral Hydrogen Observations of Some Nearby Groups of Galaxies

1980 • 1980PhDT.......101A

Authors • Appleton, Philip Noel

Abstract • High sensitivity observations of neutral hydrogen emission from the nearby M81, NGC4088 and NGC3254 groups of galaxies have been obtained. Measurements were also made of extended emission in the M51 system. In the M81 group, complex bridges of gas were found to connect the three companion galaxies to M81. It is suggested that many of these emission ridges have been formed by tidal processes within the group. A large neutral gas cloud with no obvious optical counterpart was also discovered and various explanations for its origin are discussed. A similar cloud was detected near the M51 system. Tidal interaction is probably a common phenomenon in the NGC4088 group. Observations of NGC4088 and its close companion have revealed a possible tidal tail extending away from the system. A number of HI rich dwarf galaxies with disturbed hydrogen distributions were also detected close to a lenticular galaxy NGC4026. Again it is suggested that tidal forces may be responsible for the asymmetries observed. Other galaxies in the group were found to have more regular but extensive hydrogen envelopes. A search for emission in the NGC3254 group was made but only the late-type galaxy members were detected. An investigation was also made of the stability of loose groups in 100 sq. degrees of sky centred on NGC4088. Three major gravitationally bound groups were selected from the sample leaving only 10% as possible field galaxies. The results suggest that large quantities of 'missing' mass may not be required to stabilise loose groups.

Links

• ELECTR http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:27529319