Aperture Synthesis CO(J=1—0) Observations and Near-Infrared Photometry of the Non-Barred Seyfert Galaxy NGC 5033

Aperture synthesis observations of CO(J=1-0) emission and near-infraredbroad-band photometry of the non-barred Seyfert galaxy NGC 5033 (D = 18.7 Mpc)were performed. Our 3".9 x 3".6 resolution CO observations reveal a perturbeddistribution and the kinematics of molecular gas in the center of NGC 5033; wefind the characteristic gaseous features that are widely observed in barredspiral galaxies, such as two bright CO peaks near the center (separated by ~3'' or 270 pc from the nucleus), two offset ridges of CO emission emanatingfrom the CO peaks, and a CO ring (with a radius of ~ 14'' or 1.3 kpc).Double-peaked velocity profiles are also evident near the two CO peaks,implying that these CO peaks are orbit crowding zones in a barred/ovalpotential. Although NIR data only give an upper limit of the possible barlengths, due to a large inclination of the NGC 5033 disk (i = 68 deg), our COdata clearly suggests the presence of a small (the semi-major axis of about12'' - 15'' or 1.1 - 1.4 kpc) nuclear bar (or oval structure) in the center ofthe ``non-barred'' galaxy NGC 5033. Our results demonstrate thathigh-resolution CO imaging-spectroscopy is useful to search for nuclear bars,even in highly inclined systems where isophoto fitting techniques are notapplicable. We find that the gas mass-to-dynamical mass ratio, M_gas/M_dyn, issmall (< 1%) within a radius of 2'' or 180 pc, in contrast to starburst nuclei.This implies that the starburst does not cohabitate in the type-1.5 Seyfertnucleus of N GC 5033.