Date : 6/23 (Thu) [14:00 - 16:00] @ F313
Speaker: Mr. Kazuma Mitsuda ( Univ. of Tokyo )
Title : Isophote Shapes of Early-Type Galaxies in Massive Clusters at z ~ 1 and 0
We compare the isophote shape parameter $a_{4}$ of early-ty
pe galaxies (ETGs) between $z\sim1$ and 0 as a proxy for dyn
amics to investigate when the dynamical properties of ETGs a
re characterized. We create cluster ETG samples with spectro
scopic redshifts from the Hubble Space Telescope Cluster Sup
ernova Survey for $z\sim1$ and the Sloan Digital Sky Survey
for $z\sim0$. We have developed an isophote shape analysis m
ethod which can be used for high-redshift galaxies and appli
ed the same method for both the $z\sim1$ and $0$ samples.
We find similar dependence of the $a_{4}$ parameter on the
mass and size at $z\sim1$ and 0; the main population of ETGs
changes from disky to boxy at a critical stellar mass of $\
log(M_{*}/M_{\odot})\sim11.5$ with the massive end dominated
by boxy. The similar critical mass between these redshifts
is consistent with a scenario that the mass quenching is the
origin of massive boxy ETGs. The disky ETG fraction decreas
es with increasing stellar mass both at $z\sim1$ and $0$, an
d we do not find significant difference in the fraction betw
een these redshifts in all stellar mass bins. Although uncer
tainties are large, the results suggest that the isophote sh
apes and probably dynamical properties of ETGs in massive cl
usters are characterized at $z>1$. The constant disky fracti
on between $z\sim1$ and 0 implies that the intermediate mass
ETGs in clusters should keep their dynamical properties dur
ing the size and morphological evolution in $z<1$.

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