1997A&A...325..923H

The distribution of ¹²CO(1-0) has been mapped over the spiral galaxy NGC 253 using the Swedish-ESO Submillimetre Telescope (SEST). Emission was found to extend 22.4arcmin along the major axis and to be concentrated towards the nucleus with an LSR systemic velocity of 235km/s. The CO intensity and velocity distribution suggests three subsystems: a dense, highly-rotating nuclear cloud, a disk (with a line of nodes at a position angle of 63°) extending 150arcsec each side of the nucleus containing a bar or spiral arms that are located at an azimuth of 21°, and an outer disk with a position angle of 52°. The total gas mass derived for the full extent is 2.4x10⁹M_☉, about 2% of the calculated dynamic mass of 10.5x10¹⁰M_☉.