3,  Deng, Licai  (邓李才)

     National Astronomical Observatories

Chinese Academy of Sciences

20A Datun Road, Chao-Yang District, 

Beijing, 100012,

P.R. China

Email: licai@bao.ac.cn

Title of talk: Observational constraints of Simple Stellar Population model and a new approach

Abstract: The concept of simple stellar population (SSP) in its classical scheme is defined as stars born at the same time with the same chemical abundance, and the theoretical model for it is made based on the theory of single star evolution. Observations of the real counterpart of SSPs, star clusters, show a certain deviations from the theoretical picture. There are stars observed in these stellar populations, which are straggling away from the convectional picture of stellar evolution and are very bright therefore have significant alternations to the integrated properties of SSP. In this work, we will demonstrate both observationally and theoretically that inclusion of these stragglers will bring about modifications to age and metallicity measurements of stellar populations, and hence will change the measurements of the basic parameters of galaxies in which the stellar populations are embedded.

4.  Deng, Zugan (邓祖淦)   

        Department of Physics,

Graduate School

Chinese Academy of Sciences

Beijing, 100049

P.R. China

Email: zugan_deng@yahoo.com,

Fax: +86 10 82791548

Cell: +86 10 13522150873

      Title of talk: Structural properties and scaling relations of early-type galaxies from the Sloan Digital Sky Survey

       Abstract: A representive sample of 150 local bright early-type galaxies has been selected from Data Release 2 (DR2) of Sloan Digital Sky Survey (SDSS). Two-dimensional bulge/disk light decomposition has been performed with GIM2D in both g- and r- bands by assuming that bulge and disk of a galaxy can be described with a S$\acute{e}$rsic and a exponential light profile respectively. Parameter $<a_4/a>$ which indicates deviation of isophote from pure ellipses has been carried out by IRAF task $ellipse$ for each galaxy. Analyses of our results confirm correlation between bulge-to-total light ratio (B/T) and S$\acute{e}$rsic index $n_B$ as well as between bugle and disk scale sizes as reported by former researchers. However, no significant correlation between B/T to the isophote shape parameter $<a_4/a>$ has been found. From decomposition in both g- and r- bands, it has been found that disks and bulges components have nearly the same color, this fact may show that they have nearly the same stellar populations. Both bulge and disk components satisfy color-magnitude relation (CMR) well. In average, disk components of early-type galaxies satisfy color-magnitude relation with slope as the same as that of disks of late-type spiral galaxies but slightly shift to redder side. It may imply the difference of the stellar populations in these two disks. As Investigate the distribution on Fundamental Plane in $\kappa$ space, it is found that galaxies with higher B/T appear to have distribution in $\kappa$ space tighter and closer to the so-called "zone of avoidance" than galaxies with lower B/T do. It may hint that scatter in distribution on the Fundamental Plane might be caused by the existence of disks. Our analysis indicate that for early-type galaxies kappa_1 + kappa_2 correlate with (g-r) color significantly and have trendence to correlate with B/T but none with shape parameter a_4/a.