The previous study of chemical evolution of the Galaxy is extended to the radial properties of the Galactic disk. The present model includes radial dependency of the time-dependent bimodal IMF, radial flow of material in the disk, and the change of type I supernova explosion rate with radial distance from the disk center as model parameters and observed gas and stellar density distributions and metallicity abundance gradient as observational constraints. The results of two models in this study explain the observed gas and stellar density distributions well, with the slope of the gas density gradient in the region of 4.5 kpc<r<12kpc as -0.136dex/kpc in model Y1 and -0.123dex/kpc in model Y2, respectively, which fit well the observed gradient of -0.l1dex/kpc. The abundance gradient reproduced in model Y1 is getting flatter with decreasing radius, while that in model Y2 is getting steeper, which fits better the observed abundance gradient. This result shows the necessity of exponentially increasing type I supernova explosion rate with decreasing radius in order to explain the observed abundance gradient in the disk. The fitness of observed density distribution and star formation rate distribution justifies the reliability of time-dependent bimodal IMF as a compound quantitative chemical evolution model of the Galaxy. The temporal variations of metallicity gradients for carbon, nitrogen and oxygen are also shown.

• PARK BYEONG-GON(Bohyunsan Optical Astronomy Observatory, Korea Astronomy Observatory/Department of Astronomy and Atmospheric Sciences, Kyungpook National University)
• KANG YONG HEE(Department of Earth Science Education, Kyungpook National University)
• LEE SEE-WOO(Department of Astronomy, Seoul National University)