Central spiral structure of molecular gas in Maffei 2

The distribution and kinematics of molecular gas in the central region of the barred spiral galaxy Maffei 2 were investigated using a data set of (CO)-C-12 (1-0), (CO)-C-12 (2-1), CS (2-1) lines, and 103 GHz continuum. We found that the offset ridges along the kpc-scale bar continue to the central spiral structure embedded in a weak oval structure, which is regarded as an x2 orbit in the bar potential. The spiral structure continues toward the center, diverging from the oval structure. The size of these structures is less than R similar to 100 pc. The mass concentration within R = 35 pc is estimated to be 2 x 10(8) M-circle dot. The high mass concentration is consistent with theoretical predictions concerning the creation of such a nuclear spiral structure. A comparison with tracers of dense gas and star-forming region suggests that the dense molecular gas traced by the CS (2-1) line is formed at the crossing points of the x1 and x2 orbits and the star-forming region appears after 2 x 10(5) yr, which is comparable to the free-fall time of dense gas traced by the CS line (similar to 10(5) cm(-3)).