Measurement of fast bars in a sample of early-type barred galaxies

Abstract

We present surface photometry and stellar kinematics of a sample of five SB0 galaxies: ESO 139-G009, IC 874, NGC 1308, NGC 1440 and NGC 3412. We measured their bar pattern speed using the Tremaine–Weinberg method, and derived the ratio, R, of the corotation radius to the length of the bar semimajor axis. For all the galaxies, R is consistent with being in the range from 1.0 to 1.4, i.e. that they host fast bars. This represents the largest sample of galaxies for which R has been measured in this way. Taking into account the measured distribution of R and our measurement uncertainties, we argue that this is probably the true distribution of R. If this is the case, then the Tremaine–Weinberg method finds a distribution of R which is in agreement with that obtained by hydrodynamical simulations. We compare this result with recent high-resolution N-body simulations of bars in cosmologically motivated dark matter haloes, and we conclude that these bars are not located inside centrally concentrated dark matter haloes.