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Feb/19/2008
A Demography of Galaxiesin Galaxy Clusters
with the Spectro-photometric Density Measurement.
Joo Heon Yoon 윤주헌 Sukyoung Yi 이석영
Yoon et al. 2008 ApJS in press
(astro-ph/0712.1054)
Dept. of Astronomy Yonsei Univ.
Environment Effect
Check individual clusters of galaxies.
Require homogeneous catalogue.
I. Motivation
II. Method
III. Result
J. H. Yoon
K. Schawinski
S. K. Yi
Incompleteness of SpectroscopyI. Motivation
II. Method
III. Result
1. Classical cluster catalogue (e.g. Abell) Based on eye-inspection. Projection effect, time-consuming…
2. Massive database (SDSS, 2dF, …) Systematic Search! Redshift – 3D distribution! (e.g. C4)
Fiber collision!!
Spectroscopy is incomplete!!
In a dense cluster,
fspec. ~ 65%
Incompleteness Problem!!
1. SDSS DR5 spectroscopic and photometric survey galaxies.
2. 0.05 < z < 0.1
3. Volume limited samples, r<17.77, Mr < -20.54
DataI. Motivation
II. Method
III. Result
How do we add galaxies missed by spectroscopic survey?
Galaxies in a cluster have Color-Magnitude Relation.
Cluster Member Selection via CMRI. Motivation
II. Method
III. Result
Cluster Finding with spec.+phot. data
Measure local density of galaxies
where 3σ=1Mpc, and σv = velocity dispersion
2
2
1 1( ) exp
22a
s
r
22
13 3a z
v
r r
For galaxies
with spectra.
For galaxies
without spectra.
Select red-sequence galaxies in CMR2
2
1 1( ) exp
22a
p
r
2
13ar
s p Finding the
Maximum Density Galaxy!!
Finding Galaxy Cluster!!
I. Motivation
II. Method
III. Result
spectro-photometric density
Cluster Finding with spec.+phot. data
From SDSS
I. Motivation
II. Method
III. Result
Yoon, Schawinski, Sheen, Ree, & Yi, 2008 ApJS in Press (astro-ph/0712.1054)
Efficiency of the New Measurement
From SDSS
I. Motivation
II. Method
III. Result
CTIO observation supports our method.
92% of completeness by CTIO obs.
New density
Spec. density
CTIO density
missing
A2670
Our new method.
Minimize the incompleteness.
Galaxy ClassificationI. Motivation
II. Method
III. Result
From SDSS
1. Consider spectroscopic members
2. Visual Inspection- SDSS optical combined images- Self-consistency- fracdev_r
3. Color Classification
4. Non-cluster Galaxies ρ = 0
Color & Luminosity vs. RadiusI. Motivation
II. Method
III. Result
From SDSS
Color & Luminosity
No clustocentric dependence.
I. Motivation
II. Method
III. Result
From SDSS
Color & Luminosity vs. Radius
Color & Morphology
Clustocentric dependence < R200
MDR is intrisic. The morphology-density relation
Stronger in Denser cluster
Why the Brightest Cluster Galaxy?I. Motivation
II. Method
III. Result
From SDSS
von der Linden et al. 2007 : BCG & non-BCG difference
Liu et al. 2007 : Different scaling relations. Quillen et al. 2007 : Star formation in BCGs.
Secondary of environmental effect?
BCGs in simulation Extremely huge Continuously growing BCGs are so special.
The BCGs vs. DensityI. Motivation
II. Method
III. Result
From SDSS
Denser Brighter BCGs
As well as 2nd BCGs & 3rd BCGs
No difference in their density dependence.
I. Motivation
II. Method
III. Result
From SDSS
BCGs, 2nd BCGs, & 3rd BCGs are redder
than Non-cluster galaxies.
They are different population.
The BCGs vs. NCGs
I. Motivation
II. Method
III. Result
From SDSS
CMR of ETGs
Cluster ETGs are optically red.
Non-cluster ETGs have a blue tail.
I. Motivation
II. Method
III. Result
From SDSS
Environmental Dependence
Gomez et al. 2003
I. Motivation
II. Method
III. Result
From SDSS
Environmental Dependence
I. Motivation
II. Method
III. Result
From SDSS
ρ vs. Rclustocentric
R/R200ρ
Red/B
lue
Red/B
lue
g -
r
g -
r
R/R200ρ
Galaxy position
in clusters
Local density effect
on galaxy colors>
Conclusion
New density measurement. minimize the incompleteness. A better tool for environment study.
New homogenous cluster catalogue. Color radial dependence Morphology-Density relation. Denser Environment Stronger MDR Denser Brighter BCGs Cluster Galaxies Redder than Non-cluster Galaxies. They are
different each other. BCGs and other cluster galaxies.
show the same Mr-density relation. Local galaxy density > Position in cluster
New density measurement. minimize the incompleteness. A better tool for environment study.
New homogenous cluster catalogue. Color radial dependence Morphology-Density relation. Denser Environment Stronger MDR Denser Brighter BCGs Cluster Galaxies Redder than Non-cluster Galaxies. They are
different each other. BCGs and other cluster galaxies.
show the same Mr-density relation. Local galaxy density > Position in cluster
All color logos
All color logos
All color logos
Measuring Density (Schawinski et al. 2006)
DEC
RA z
DEC
RA z
Line of Sight
1Mpc
I. Motivation
II. Method
III. Result
3 X σ v
A Demography of Cluster GalaxiesI. Motivation
II. Method
III. Result
From SDSS
Efficiency of the New Measurement
From SDSS
I. Motivation
II. Method
III. Result
BCGs are generally in centers.
BCG & MDG separation smaller, better.
Efficiency of the New Measurement
From SDSS
I. Motivation
II. Method
III. Result
CMR efficiency test with spectroscopic, early-type (fracdev_r > 0.95) member galaxies.
Completeness= Purity =
# of members in red-sequence100
# of all members
# of members in red-sequence100
# of all red-sequence
90% cover
15% contamination
Efficiency of the New Measurement
From SDSS
I. Motivation
II. Method
III. Result
Our new density parameter
Good tracer of cluster size and mass.
From SDSS
Spectrum analysis Line indices, SFR, etc. ― Clustocentric radius
SH’s SAM clusters with Khochfar’s semi-analytical model vs. Observed clusters Constrain SAM.
Future Study