SMA Research: Dense warm molecular gas ring in NGC1097

NGC1097 is a spectacular galaxy displaying very rich structures. With decreasing radius it shows spiral arms, outer bar, ring, inner bar and nuclear spiral. Panchromatic (ultraviolet, optical, infrared, radio) observational data of stars and gas help understand how gas, stars and various dynamical structures of this galaxy evolves with time. Our high resolution (3"x2") SMA image of molecular gas CO (3-2) emission displays the beautiful gas-ring associated with the starburst ring and the bright nuclear emission peak. Comparing with published literature we see that the relative dominance of the nuclear peak increases with higher orders of transitions. On the contrary the two diametrically opposite regions (dust-lanes connecting the ring) do not show brighter emission, as seen in lower transitions. This variation possibly suggest difference between gas flow and/or excitation processes. Comparing with data at other wavelengths, tracing different phases of the interstellar medium or different age of the stellar population, evolutionary history of NGC1097 can be explored. Molecular gas condenses to form stars. The most massive and youngest of them are seen in ultra violet emission (near-UV from GALEX telescope). If the stellar structure evolves with time, near-IR (tracing cool old stars) image may differ from UV images. Possibly in the 2MASS (K-band) image the inner bar connecting the gas-ring looks more like a tightly wound spiral than a ring. Stars eventually age and die in explosions, sprinkling metals in to the ambient space forming dust grains and polycyclic aromatic hydrocarbon (Spitzer telescope image). From this sprinkled metal we got the Iron in our blood, and Carbon and Oxygen in our body. Carbon-mono-oxide gas emit a spectral line, and SMA telescope can do a very good Doppler-effect analysis to investigate the dynamics and ultimately life-cycle of galaxies.


Ananda Hota (ASIAA), 2009