High-Resolution Berkeley-Illinois-Maryland Association Observations of CO, HCN, and 13CO in NGC 1068

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Abstract
We present high-resolution CO, HCN, and (CO)-C-13 maps of the inner arcminute of NGC 1068. The maps were made by combining observations from the Berkeley-Illinois-Maryland Association (BIMA) interferometer with single-dish data from the NRAO 12 m telescope; the maps therefore do not suffer the usual interferometric problems associated with the lack of small spatial frequency visibilities. Several features appear in the CO map which have not previously been observed: (1) a firm detection of CO line emission from a compact region centered on the nucleus of the galaxy; (2) the detection of a triplet velocity structure characteristic of kinematically independent regions shown on the spectrum of the unresolved nuclear emission; and (3) the detection of a molecular bar, the extent and position angle of which are in good agreement with the 2 mu m stellar bar. As seen in previous high-resolution images, the most intense CO emission is nonnuclear at a typical distance of 15'' from the center of NGC 1068. The structure and kinematics of this emission imply that this gas is distributed along the inner spiral arms and not in a ring. The bar's kinematic influence on the molecular gas in the spiral arms is modest, with typical ordered noncircular motions of less than or similar to 30 km s(-1) in the plane of the galaxy. Interior to the spiral arms, the bar's influence is more dramatic, as reflected by the twisted isovelocity contours in the CO and HCN velocity fields. We derive a pattern speed for the bar of 150-170 km s(-1) kpc(-1). The position angle of the bar, similar to 63 degrees, is close to that of the jet emanating from the nucleus, similar to 33 degrees. The surface density of molecular gas within the central 100 pc radius of NGC 1068 is the same as that in the central 200 pc radius in the Milky Way to within the uncertainties. There is evidence for an m = 1 kinematic mode in NGC 1068; we find the kinematic center of rotation to be displaced from the radio continuum center by about 2.''9, or 200 pc. The HCN image, in agreement with recent results from other interferometers and in contrast to the CO map, shows a strong concentration of emission centered on the nucleus. The ratio of integrated intensities of the HCN emission to that of CO is about 0.4 and is the highest ratio measured in the central region of any galaxy. The (CO)-C-13 emission follows the general distribution of the CO emission. The average CO/(CO)-C-13 ratio of integrated intensities in the spiral arms is about 13; this is similar to what is observed in the centers of other nearby galaxies.

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