Mathematics – Logic
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003phdt........14g&link_type=abstract
University of Sao Paulo Ph.D. thesis; supervisor: Dr. R. E. de Souza
Mathematics
Logic
2
Scientific paper
We have done a detailed study on the structural and kinematical properties of lenticular and early- and late-type spiral galaxies with bars, aiming to explore the formation and evolution processes of stellar bars in galaxies, and their implications on the global formation and evolution of galaxies. Using high signal-to-noise spectra obtained along the major and minor axes of the bars in a sample of 14 galaxies, we have determined, with an algorithm properly developed for this task, the stellar velocity distribution in the bars' vertical axis, in several points, reaching 20'' from the center. With these data, it was possible to develop a diagnostic tool that allows one to estimate the ages of bars, and distinguish between recently formed bars and evolved bars. Furthermore, we could evaluate the vertical structure of disks and bars in galaxies. Through realistic N-body simulations, we have studied the necessary conditions to the formation of bars in galaxies, as well as the time scale involved in the processes which give bars an important vertical structure. Finally, using images obtained in B, V, R, I and Ks for a sample of 19 galaxies, and images obtained in R for a sample of 51 galaxies, including elliptical galaxies, we have performed a detailed structural analysis in galaxies covering the whole Hubble morphological sequence, determining the structural parameters which describe the bulge and the disk in these galaxies, as well as obtaining residual images which reveal important sub-structures. In order to perform this analysis we have developed a specific algorithm, and built an atlas of structural analysis in galaxies. Among the main results obtained, we point out: (i) there are vertically thin and thick bars and this difference is caused by a difference in the ages of the bars; (ii) the bar thickening process, as we have determined, is slow (~ 5-10 Gyr); (iii) the current scenario for bar formation is not able to explain naturally the existence of bars in galaxies which are kinematically hot and have prominent bulges; (iv) we suggest a new mechanism for bar formation in galaxies, which can account for the serious drawbacks confronted in the current scenario, as well as explain the existence of barred galaxies in which the disk component is almost absent, a discovery which was also a product of this work; (v) bulges in lenticular and in spiral galaxies are, at least partially, formed through the secular evolutionary processes in bars; (vi) during its evolution, a bar grows stronger by capturing stars from the disk, which becomes fainter, in agreement with recent numerical and analytical results; (vii) around 1/3 of the elliptical galaxies harbor inner disks, and (viii) visual morphological classification of galaxies is wrong in nearly 1/3 of the elliptical and lenticular galaxies.
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