Cluster Cosmology at LPPC
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Transcript of Cluster Cosmology at LPPC
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Cluster Cosmology at LPPCIlluminating Dark Energy with BCS and PISCO
F. William High2nd Year Grad Student
Harvard Univ Dept of Physics
Monday, 21 August 2006
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21 August 2006 Clusters@LPPC F. William High
Cluster Cosmology
Dark Energy
Dark Energy dominates
dominates
t ~ 9 Gyr t ~ 3 Gyr t = 0
Galaxies start
Galaxies start clustering
clustering
Big Bang
Big Bang
Galaxies start
Galaxies start formingforming
t ~ 1 Gyr
t ~ 14 Gyr
TodayToday
Redshift z: Redshift z:
1 + z = 1 + z = λλ(observed) / (observed) / λλ(emitted)(emitted)
z = 0 z ~ ½ z ~ 2
z ~ 6
z = ∞
Dark Energy
Dark Energy takes effect
takes effect
t ~ 7 Gyrz ~ 1
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21 August 2006 Clusters@LPPC F. William High
Cluster Cosmology: Illuminating Dark Energy
Accelerating expansion Λ: Einstein’s cosmo-
logical constant w: eqn of state (w = -1)
Cluster abundance versus redshift Depends heavily on Λ and
w Overall normalization
depends on σ8
1/10 of the sky1/10 of the sky
redshiftredshift
Nu
mb
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of
Nu
mb
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of
clu
ste
rsc
lus
ters
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21 August 2006 Clusters@LPPC F. William High
Discovering Clusters
SZ effect APEX, ACT, SPT, … Redshift independent
signal in mm
mm-wavemm-wave
X-rayX-ray
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21 August 2006 Clusters@LPPC F. William High
BCS (500 clusters), then PISCO (3000 clusters), then DES (the rest)BCS (500 clusters), then PISCO (3000 clusters), then DES (the rest)THE RESTTHE REST
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21 August 2006 Clusters@LPPC F. William High
Two Challenges
Mass of clusters?
Solution: BCSBCS
Distance to clusters?
Solution: PISCOPISCO
Observable:
Probability:
Matter evolution:
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21 August 2006 Clusters@LPPC F. William High
BCS
Blanco Cosmology SurveyPre-SPTTo z ~ 1Training set for SPT and PISCOWeak gravitational lensing to calibrate SZ
cluster mass estimatorPI: Joe Mohr (U Illinois)
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21 August 2006 Clusters@LPPC F. William High
PISCO
PParallel IImager for SSouthern CCosmological OObservations
Dedicated camera to measure redshift of high-z clusters Field of view matched to size of high redshift
clusters: 5’ = 1 Mpc at z = ½, clusters are 1-10 Mpc across
Highest possible efficiency broadband photometer: 4 simultaneoussimultaneous bands
To be mounted on 6.5m Magellan, Chile
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21 August 2006 Clusters@LPPC F. William High
PISCO: Photo-z
Principle: measure differential broadband flux (color) of objects with broad features in spectrum
Photo-z gives redshifts (to 10%) from the colors of luminous red galaxies (LRG)
Cluster member galaxies have scatter in redshift at 3% level
PISCO measures photo-z’s PISCO measures photo-z’s of of allall galaxies in a cluster at galaxies in a cluster at once, in a once, in a singlesingle exposure exposure
LRG LRG spectrumspectrum
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21 August 2006 Clusters@LPPC F. William High
PISCO: Design
Ideal broadband photometer!Ideal broadband photometer!
Dichroic beamsplittersDichroic beamsplitters define bandpassesdefine bandpasses
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21 August 2006 Clusters@LPPC F. William High
PISCO: Design
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21 August 2006 Clusters@LPPC F. William High
CC@LPPC Summary
Use weak gravitational lensing to calibrate other cluster mass-observables
Improve cluster mass estimation for all future surveys
Status: first year data reduced, ready to do start WL study in September
Characterize DE with clusters quickly, cheaply, efficiently
Can get z’s of all SPT clusters in 10 nights at Magellan!
Status: CCD’s in hand, CCD control online, design soon finalized, Carnegie enthusiastic, …
BCSBCS PISCOPISCO