QUANTITATIVE MORPHOLOGY OF BARS IN SPIRAL GALAXIES

As suggested by numerical simulations, the axis ratio of the bar is a fundamental parameter to describe the dynamical evolution of a barred galaxy. In a first-order approximation considering bars as elliptical features, visual measurements of bar axis ratios and lengths of 136 spiral galaxies were performed on photographs of good linear scale. Despite the limitations affecting such measurements, morphological properties of bars in spirals along the Hubble sequence as well as the relationship between the bar axis ratio and nuclear star formation activity are studied. It is found that the relative length of bars in early-type galaxies is, on average, about a factor of 3 larger than the length observed in late-type spirals. Also, a relation between bar lengths and bulge diameters is observed for both early-type and late-type spirals, confirming results from previous works. Furthermore, although the number of objects is small, there is an apparent correlation between the presence of nuclear star formation activity and the bar axis ratio: about 71% of the starburst galaxies included in the sample have a strong bar (b/a<0.6). The introduction of these quantitative parameters in galaxy classification schemes is discussed. © 1995 American Astronomical Society.