Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007phdt........37h&link_type=abstract
Ph.D Thesis submitted to Indian Institute of Science, India, 263 pages.
Astronomy and Astrophysics
Astronomy
Gas Loss, Galaxies, Radio Astronomy, Galaxies - Radio Continuum Emission, Galaxies - Hi Emission, Starbust Galaxies, Superwind Galaxy, Cluster Galaxies, Active Galaxies, Galaxies - Star Formation, Gmrt Observations, Galactic Wind, Outflow, Feedback, Galaxy Evolution, Galaxy Tramsformation, Ram Pressure Stripping, Seyfert Galaxy, Agn, Jet
Scientific paper
The work in this thesis involves detailed multi-frequency radio continuum (from 325 MHz to 15 GHz) and HI spectroscopic studies of a few representative nearby galaxies which are experiencing gas-loss from their disks due to different physical processes. These processes are starburst-driven galactic wind or superwind outflow (NGC1482, NGC6764), active galactic nucleus (AGN)-driven nuclear outflow (NGC6764, NGC4438), ram pressure stripping and tidal interactions (NGC4438, Holmberg 124, Abell 1367). Gas-loss could affect the evolution of individual galaxies with age as well as their evolution with cosmic epoch. We have made use of both the Giant Metrewave Radio Telescope (GMRT) and the Very Large Array (VLA) for our study. In this study we have found a number of interesting results where different gas-loss processes have modified the morphology and kinematics of the ISM and/or the stellar distribution of the respective parent galaxies. We have found evidence of blue-shifted HI absorption lines driven outwards by the starburst-driven superwinds and/or AGN-driven nuclear outlows (feedback processes). The synchrotron plasma outflowing from an AGN in a composite galaxy has been suggested to be interacting with the superwind which also drives other components of the ISM outwards. In groups or clusters of galaxies we have discovered an HI-loop, HI-tails, regions of compressed HI, trailing velocity fields, slow-rotating extra-planar gas, displaced ISM and asymmetries in various radio continuum or HI-features as clear evidences of ram pressure stripping mechanism affecting the group- and cluster- galaxies. The results obtained from this study illustrates the manifestations of gas loss processes in galaxies existing in different environments, and should provide valuable insights for future investigations with larger statistical samples towards a more complete understanding of feedback processes and galaxy pre-processing in galaxies and, their implications on galaxy evolution.
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