Linear analysis of the kinematics

By performing a standard linear analysis of the kinematics (e.g. Binney & Tremaine 1987) it is possible to obtain the location of the main resonances, co-rotation (CR) and the inner Linblad resonances (ILRs). We use results from numerical simulations that place CR close to the bar semimajor axis (Athanassoula 1992), to infer a bar pattern speed of 3 km s^-1 arcsec^-1 (32 km s^-1 kpc^-1) . This implies the existence of two ILRs, at 2 arcsec (180 pc, inner ILR) and at 12 arcsec (1100 pc, outer ILR) . From OVRO CO observations of the central part of the galaxy, Kenney et al. (1992) obtain values of 180 pc for the iILR and 460 pc for the oILR; this latter value is a lower limit derived from their upper limit to the bar pattern speed of 66 km s^-1 kpc^-1, and thus is compatible with our results.