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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.
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