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Session 80 - Stellar Population in Cluster Galaxies.
Display session, Wednesday, January 15
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.
Program listing for Wednesday