SIMBAD references

Most of the giant molecular clouds (GMCs) in M33 are connected with spiral-like gaseous arms (filaments) with the exception of the inner 2 kpc region where the link between the arms and GMCs disappears (see Tosaki et al.). We check whether this may be caused by dynamical friction retarding the clouds. Using a semi-analytical model for this galaxy, we calculate the dynamics of GMCs of different masses situated at different initial galactocentric distances in the disc plane. We demonstrate that dynamical friction may really change the orbits of GMCs in the central 2-kpc region. However, in this case the typical lifetimes of GMCs should be close to or greater than 108 yr, which is larger than the usually accepted values.