Cluster Cosmology at LPPC

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Cluster Cosmology at LPPC

• Illuminating Dark Energy with BCS and PISCO
• F. William High
• 2nd Year Grad Student
• Harvard Univ Dept of Physics
• Monday, 21 August 2006

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Cluster Cosmology
Redshift z 1 z
?(observed) / ?(emitted)
Today
Big Bang
Galaxies start forming
Dark Energy takes effect
Dark Energy dominates
Galaxies start clustering
t 9 Gyr
t 3 Gyr
t 0
t 14 Gyr
t 7 Gyr
z 0
z ½
z 2
z 8
z 1
t 1 Gyr
z 6
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Cluster Cosmology Illuminating Dark Energy

• Accelerating expansion
• ? Einsteins cosmo-logical constant
• w eqn of state (w -1)
• Cluster abundance versus redshift
• Depends heavily on ? and w
• Overall normalization depends on s8

1/10 of the sky
Number of clusters
redshift
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Discovering Clusters

• SZ effect
• APEX, ACT, SPT,
• Redshift independent signal in mm

mm-wave
X-ray
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THE REST
BCS (500 clusters), then PISCO (3000 clusters),
then DES (the rest)
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Two Challenges

• Mass of clusters?
• Solution BCS

• Distance to clusters?
• Solution PISCO

Probability
Matter evolution
Observable
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BCS

• Blanco Cosmology Survey
• Pre-SPT
• To z 1
• Training set for SPT and PISCO
• Weak gravitational lensing to calibrate SZ
  cluster mass estimator
• PI Joe Mohr (U Illinois)

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PISCO

• Parallel Imager for Southern Cosmological
  Observations
• 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 simultaneous bands
• To be mounted on 6.5m Magellan, Chile

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PISCO Photo-z
LRG spectrum

• 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-zs of all galaxies in a
  cluster at once, in a single exposure

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PISCO Design
Ideal broadband photometer!
Dichroic beamsplitters define bandpasses
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PISCO Design
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PISCO Status

• Concept completed
• Detectors in hand, ready to test
• Simulate expected bandpasses
• Simulate photo-z signals

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PISCO To Do List

• Modeling
• Optimize survey strategy
• Simulate photo-z
• Hardware
• Finish design, order optics
• Begin fabrication
• Characterize/optimize electronics and detectors
• Integrate, test system
• Software
• Pull existing software (object detection,
  photometry, photo-z, ) into one pipeline
• Test with real data
• Integrate with instrument

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PISCO Collaboration

• Christopher Stubbs
• Tony Stark (SAO)
• John Geary (CfA)
• James Battat (LPPC)
• Ned Henry (LPPC)
• SPT John Carlstrom (Chicago), Joe Mohr
  (Illinois),

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Constant Cosmological Constant?

• Ultimate goal with BCS and PISCO measure whether
  dark energy is a constant vacuum energy
• Dark (vacuum) energy equation of state parameter
  w p/?

Dark energy eqn of state parameter
Dark energy
Matter d evolves as
Hubble parameter
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CC_at_LPPC Summary
BCS
PISCO

• 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 zs of all SPT clusters in 10 nights at
  Magellan!
• Status CCDs in hand, CCD control online, design
  soon finalized, Carnegie enthusiastic,