We present ^ { 12 } CO ( 1-0 ) observations in the central 4.5 { kpc } ( 1 \arcmin ) of the { H \alpha } /Radio lobe galaxy NGC 3079 with the Nobeyama Millimeter Array .
The molecular gas shows four components : a main disk , spiral arms , a nuclear disk , and a nuclear core .
The main disk extends along the galaxy major axis .
We detected its central 2 { kpc } radius , while its full extent is beyond our spatial coverage .
Molecular gas is smoothly distributed in the main disk , having a gas mass of 5 \times 10 ^ { 9 } M _ { \odot } within the central \sim 2 { kpc } radius .
The spiral arms are superimposed on the main disk .
Abrupt velocity changes of up to \sim 200 { km s ^ { -1 } } are observed along the spiral arms in S -shaped twists of isovelocity contours and double velocity-peaked features on the spectra .
The nuclear disk with \sim 600 { pc } radius appears in position-velocity ( PV ) diagrams , having an intense concentration of molecular gas .
Its appearance on PV diagrams is indicative of oval motions of the gas , rather than circular .
The nuclear disk and spiral arms form the so-called “ figure-of-eight ” pattern on a PV diagram .
The nuclear core is more compact than our current resolution ( 2 \arcsec = 150 { pc } ) , and has a gas mass of 3 \times 10 ^ { 8 } M _ { \odot } within the central 150 { pc } .
Though it is unresolved , the nuclear core shows a very high velocity \sim 200 { km s ^ { -1 } } even at the radius of \sim 100 { pc } on the PV diagram .

We propose a model that NGC 3079 contains a weak bar .
The weak bar model explains the observed features of the main disk , spiral arms , and nuclear disk .
The main disk and spiral arms result from gaseous x _ { 1 } -orbits and associated crowding respectively .
The nuclear disk arises from gaseous x _ { 2 } -orbits .
The gas concentration in the nuclear disk could be explained by the expected gas-fueling mechanism : the gas on x _ { 1 } -orbits flows along spiral arms ( or offset shocks ) , colliding with the gas on x _ { 2 } -orbits , and accumulating onto the nuclear disk .
Assuming that the gas moves nearly along the spiral arms which run perpendicular to the line-of-sight , the pattern speed of the bar is estimated to be 55 \pm 10 { km s ^ { -1 } kpc ^ { -1 } } .
The high velocity of the nuclear core can not be explained by our model for a bar .
Thus we attribute it to a central massive core with a dynamical mass of 10 ^ { 9 } M _ { \odot } within the central 100 { pc } .
This mass is three orders of magnitude more massive than that of a central black hole in this galaxy .