CO(2-1) emission from the interacting galaxy pair NGC 3256
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Abstract
We have mapped the J = 2 -> 1 CO emission in the merging galaxy pair, NGC 3256. Molecular gas is distributed over an area of radius 34" (i.e., 6 kpc); the CO "luminosity," 6.4 x 10^9^ K km s^-1^ pc^2^, puts this galaxy among the group of three or four with the highest gas masses yet found, 3.1 x 10^10^ M_sun_. Although the total far-infrared luminosity is large, L(40-400 microns) ~ 3 x 10^11^ L_sun_, the L_FIR_/M(H_2_) ratio is enhanced by a factor of only about 3 compared to gas-rich spirals like the Milky Way. Our observations show that the molecular gas in this system is still widely dispersed across the almost completely merged disks. The systemic velocity, 2762 +/- 10 km s^-1^, is in good agreement with the less well-determined optical value. The large extent of the CO emission and the unusually high mass of molecular gas, together with the unremarkable value for L_FIR_/M(N_2_), suggest that in NGC 3256 the merger is not very advanced.