Session 80 - Stellar Population in Cluster Galaxies.
Display session, Wednesday, January 15
Metropolitan Ballroom,

## [80.03] Structure and Star Formation Rates in Nearby and Distant Field Galaxies

M. Takamiya (U. Chicago)

The nature and evolution of galaxies have become important issues in cosmology. To quantify the amount of evolution in galaxies, I am analysing the structure of nearby and distant galaxies applying a novel technique (Takamiya amp; Kron 1995) to the images of galaxies in the B, V, and I bands. Metric sizes and high spatial-frequency powers of galaxies are the basic parameters that define our technique for estimating the star formation rate. Our method for measuring the star formation rate has a simple physical explanation: galaxies in stages of high star formation rates show an enhanced flux originated from extreme Population I stars distributed in a clumpy fashion, while quiescent galaxies show a smoother light distribution.

The sample of nearby galaxies used in this study was taken from the catalog of Frei et al. (1996). The powers at high spatial-frequencies of nearby galaxies are well correlated with the H\alpha equivalent width and the B-V colour. The sample of distant galaxies with redshifts 0.2< z <1 was taken from the redshift catalog of Cowie (1996). The high spatial-frequency power of distant galaxies shows a good correlation with B_450-I_814 colour. However, the morphological Hubble types seem loosly related to the power at high spatial-frequencies. To further understand these preliminary results, I am increasing the number of distant as well as nearby galaxies in our samples.

We present the high spatial frequency powers as measured in four bands (U_450, B_450, V_660, I_814) as a function of redshift.