Abstract
The circumnuclear (inner kiloparsec) regions of spiral galaxies are time-dependent systems whose morphology and dynamics can change significantly over less than a Hubble time. To develop an insight into this evolution it is important to study the fate of gas driven towards the central parts of a galaxy especially near the dynamical resonances. The panoply of CO morphologies displayed by the circumnuclear regions of starburst and nonstarburst galaxies such as NGC 3504, NGC 3351, NGC 7479, NGC 6951, etc, (Kenney, these proceedings) is not yet clearly understood. Another unsettled issue concerns the criteria for star formation in the circumnuclear region where, in contrast to the outer disk, the rotation curve is nearly solid-body and rises rapidly. These issues need to be resolved; the gas mass fraction, the radial variation of SFR (star formation rate) and its interplay with the gas kinematics can shed light not only on the temporal evolution of the circumnuclear CO morphology but also on secular evolution through the destruction and creation of new stellar components. For instance, stellar bars can be destroyed by an increase in the central gas mass concentration of a few % of the total galaxy mass while mechanisms to build or enhance a bulge by vertical scattering of the stars in a compact circumnuclear stellar disk have been proposed (Sellwood 1994, Pfenniger & Norman 1990). We have carried out a study of the circumnuclear region of NGC 4102 with these important issues in mind. NGC 4102, a LINER/HII, SABb spiral galaxy at a distance of 17 Mpc with a bar and/or lens feature qualifies as one of the most luminous nearby starbursts (Devereux 1989) and seems to be in a very early phase of evolution. The outflow timescale of the central starburst wind in NGC 4102, determined from optical spectroscopy of the ionized swept-up gas, is 106 years (Boer 1994), suggesting it is at an earlier evolutionary phase than M82 and NGC 253 whose outflow timescales are significantly larger.
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