ABSTRACT

We model the kinematics of the molecular gas in the nearly edge-on disk in M82, by considering velocity and surface density perturbations caused by a possible rotating kpc long bar consistent with the angle of the bar observed from K (2.2 μm) isophotes. A model with a bar that has an Inner Linblad Resonance (ILR) at r ∼ 10″ ∼ 150 pc fits the molecular observations of the inner torus. The clouds have a cloud-cloud velocity dispersion of less than ∼ 30 km s-1.

The nearby “starburst” galaxy M82 is one of the most powerful infrared sources which is the result of a high star formation (SF) rate. There is a high concentration of molecular gas (∼ 5.5 × 107 M⊙) in the vicinity of the central starbursting region. The double lobed molecular structure observed is thought to be in the form of a rotating ring with a radius of approximately 250 pc (e.g. Weliachew et al. 1984). In the near infrared K or 2.2 μm band, there is a plateau of emission which is interpreted as evidence for a kpc long bar (Telesco et al. 1991) which may have caused the molecular gas to sink into the nuclear region. This mechanism for fueling a starburst has been predicted by numerical simulations of galaxy-galaxy collisions which include gas dynamics (e.g. Barnes and Hernquist 1991).