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Session 89 - Star-forming Galaxies.
Oral session, Friday, January 09
International Ballroom East,

[89.01] MOLECULAR GAS and STARBURSTS in the CIRCUMNUCLEAR regions of SPIRAL galaxies

S. Jogee (Yale University)

In my thesis, I investigate the properties of molecular gas and star formation in the circumnuclear (inner kpc) region of spirals. I analyze a sample of 10 nearby luminous starburst, and non-starburst galaxies using 2'' resolution interferometric CO (J=1->0) observations, in conjunction with ground-based and HST optical images, radio continuum, near-infrared, X-ray, and HI data. In particular, (a) I investigate where the extra mass ends up as gas reaches the inner few kpc by studying inflow processes, star formation, and outflow processes. I compare the distributions, kinematics, and star-forming efficiency of the molecular gas in relation to the stellar potential. In NGC 2782, I present evidence that a pair of nuclear bars is fuelling a powerful central starburst. I estimate the gas inflow rate and future evolution in order to probe the possibility that nuclear bars and the `bar within bar' instability may be an efficient way to fuel central AGNs/starbursts. Mass outflows are as important as gas inflows for the evolution of the inner kpc. I present multi-wavelength evidence that NGC 2782 harbors a remarkable starburst-driven outflow which is dynamically very young. I compare the energetics of the hot, warm and cold phases of the ISM which the outflow is driving out of the central kpc. (b) I study the triggering and evolution of nuclear starbursts. I investigate why galaxies with comparable amount of circumnuclear molecular gas convert the gas into stars over timescales that differ by orders of magnitude. I present evidence that the gas consumption timescale may be correlated with the gas morphology and kinematics, and sketch likely evolutionary consequences. I show that gravitational instability models may describe the onset of star formation in the circumnuclear regions of some spirals. I examine the possibility that starbursts may be the normal mode of star formation in the centers of spirals.

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