Secular evolution and structural properties of stellar bars in galaxies

Abstract

I present results from the modelling of stellar bars in nearly 300 barred galaxies in the local universe through parametric multicomponent multiband image fitting. The surface brightness radial profile of bars is described using a Sérsic function and parameters, such as the bar effective radius, ellipticity, boxiness, length and mass, and bar-to-total luminosity and mass ratios, are determined, which is unprecedented for a sample of this size. The properties of bars in galaxies with classical bulges and pseudo-bulges are compared. For a fixed bar-to-total mass ratio, pseudo-bulges are on average significantly less massive than classical bulges, indicating that, if pseudo-bulges are formed through bars, further processes are necessary to build a classical bulge. I find a correlation between bar ellipticity and boxiness, and define a new parameter as the product of these two quantities. I also find correlations between this product and the normalized bar size, between the sizes of bars and bulges, and between the normalized bar size and bulge-to-total ratio. Bars with different ellipticities follow parallel lines in the latter two correlations. These correlations can arise if, starting off with different normalized sizes and ellipticities, bars grow longer and stronger with dynamical age, as a result of angular momentum exchange between the inner and outer parts of galaxies, consistent with previous theoretical predictions. A plausible consequence is that bar pattern speeds should become lower with bar dynamical age and towards galaxies with more prominent bulges. © 2011 The Author Monthly Notices of the Royal Astronomical Society © 2011 RAS.