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We have used Spitzer images of a sample of 68 barred spiral galaxies in thelocal universe to make systematic measurements of bar length and bar strength.We combine these with precise determinations of the corotation radii associatedwith the bars, taken from our previous study which used the phase change fromradial inflow to radial outflow of gas at corotation, based on high resolutiontwo-dimensional velocity fields in H{\alpha} taken with a Fabry-P\'erotspectrometer. After presenting the histograms of the derived bar parameters, westudy their dependence on the galaxy morphological type and on the totalstellar mass of the host galaxy, and then produce a set of parametric plots.These include the bar pattern speed versus bar length, the pattern speednormalized with the characteristic pattern speed of the outer disk versus thebar strength, and the normalized pattern speed versus R, the ratio ofcorotation radius to bar length. To provide guide-lines for our interpretationwe used a recently published simulations, including disk and dark matter halocomponents. Our most striking conclusion is that bars with values of R < 1.4,previously considered dynamically fast rotators, can be among the slowestrotators both in absolute terms and when their pattern speeds are normalized.The simulations confirm that this is because as the bars are braked they cangrow longer more quickly than the outward drift of the corotation radius. Weconclude that dark matter halos have indeed slowed down the rotation of bars onGyr timescales.

Kinematic clues to bar evolution for galaxies in the local universe: why the fastest rotating bars are rotating most slowly