2010A&A...510A..52C

We present ¹²CO(1-0) and ¹²CO(2-1) maps of the interacting Seyfert 2/LINER galaxy NGC5953 obtained with the IRAM interferometer at resolutions of 2.1"x1.4" and 1.1"x0.7," respectively. We also present single-dish IRAM 30m observations of the central region of NGC5953 for the ¹²CO(1-0), ¹²CO(2-1), and HCN(1-0) transitions at resolutions of 22'', 12'', and 29'', respectively. The CO emission is distributed over a disk of diameter ∼16''(∼2.2 kpc), within which are several, randomly distributed peaks. The strongest peak does not coincide with the nucleus, but is instead offset from the center, ∼2-3'' (∼340pc) toward the west/southwest. The kinematics of the molecular component are quite regular, as is typical of a rotating disk. We also compared the ¹²CO distribution of NGC5953 with observations at other wavelengths in order to study correlations between different tracers of the interstellar medium. The HST/F606W WFPC2 images show flocculent spiral structures and an ``S-shape'' feature >60pc in radius, possibly associated with a nuclear bar or with the radio jet. A two-dimensional bulge/disk decomposition of the H-band (HST/F160W) and 3.6 µm (Spitzer/IRAC) images reveals a circumnuclear ``ring'' ∼10-14'' in diameter, roughly coincident in size with the CO disk and with a star-forming ring previously identified in ionized gas. This ring is not present in the near-infrared (NIR) J-K color image, nor is it present in the ``dust-only'' image constructed from the 8 µm IRAC map. The implication is that the excess residual ring is stellar, with colors similar to the surrounding disk. We interpret this ring, visible in ionized gas, which appears as stars in the NIR, and with no sign of hot dust, as due to a red super giant population at least 10-15Myr old. However, star formation is still ongoing in the disk and in the ring itself. Using NIR images, we computed the gravity torques exerted by the stellar potential on the gas. The torques are predominantly positive in both ¹²CO(1-0) and ¹²CO(2-1), suggesting that gas is not flowing into the center, and less than 5% of the gas angular momentum is exchanged in each rotation. This comes from the regular and almost axisymmetric total mass and gas distributions in the center of the galaxy. In NGC5953, the AGN is apparently not being actively fueled in the current epoch.