DUST AND MOLECULAR GAS IN THE BARRED SPIRAL GALAXY NGC-1530

We present Berkeley-Illinois-Maryland Array CO (J = 1-0) interferometry at 3 '' resolution, NRAO 12 m single-dish observations, and KPNO near-infrared observations of the strongly barred spiral galaxy NGC 1530. The CO observations reveal that the molecular gas in the central regions is concentrated near the intersection of the dust lanes and a nuclear dust ring. However, the CO morphology is more complex than a simple ''twin peaks'' morphology reported for some other barred spirals and is better approximated by a partial ring or partial two-armed spiral. We combine the near-infrared observations with optical observations of the galaxy to form optical-infrared color maps. These maps reveal an inner dust ring not visible using optical colors alone. We use a radiative transfer model that accounts for both absorption and multiple scattering to model the expected colors for a given amount of dust and a given vertical scale height of the dust relative to the stars. We then use this model to derive the optical depth and relative scale height of the dust throughout the bar and nuclear dust ring of NGC 1530. The peak face-on optical depth we derive is approximately tau v = 4. We also show that the ratio of the dust optical depth to the CO emission varies between the bar dust lanes and the nuclear dust ring by a factor of 2. CO emission is relatively enhanced in the nuclear dust ring, which we attribute to heating of the molecular gas by the ongoing star formation in the nuclear region.