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

2. F. William High21 August 2006Clusters@LPPC Cluster Cosmology Dark Energy dominates t ~ 9 Gyrt ~ 3 Gyrt = 0 Galaxies start clustering Big Bang Galaxies start forming t ~ 1 Gyr t ~ 14 Gyr Today Redshift z: 1 + z = λ(observed) / λ(emitted) z = 0z ~ ½z ~ 2 z ~ 6 z = ∞ Dark Energy takes effect t ~ 7 Gyr z ~ 1

3. F. William High21 August 2006Clusters@LPPC 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 σ 8 1/10 of the sky redshift Number of clusters

4. F. William High21 August 2006Clusters@LPPC Discovering Clusters SZ effect APEX, ACT, SPT, … Redshift independent signal in mm mm-wave X-ray

5. F. William High21 August 2006Clusters@LPPC BCS (500 clusters), then PISCO (3000 clusters), then DES (the rest) THE REST

6. F. William High21 August 2006Clusters@LPPC Two Challenges Mass of clusters? BCS Solution: BCS Distance to clusters? PISCO Solution: PISCO Observable: Probability: Matter evolution:

7. F. William High21 August 2006Clusters@LPPC 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)

8. F. William High21 August 2006Clusters@LPPC PISCO PISC O 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 simultaneous  Highest possible efficiency broadband photometer: 4 simultaneous bands To be mounted on 6.5m Magellan, Chile

9. F. William High21 August 2006Clusters@LPPC 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 of all galaxies in a cluster at once, in a single exposure PISCO measures photo-z’s of all galaxies in a cluster at once, in a single exposure LRG spectrum

10. F. William High21 August 2006Clusters@LPPC PISCO: Design Ideal broadband photometer! Dichroic beamsplitters define bandpasses

11. F. William High21 August 2006Clusters@LPPC PISCO: Design

12. F. William High21 August 2006Clusters@LPPC PISCO: Status Concept completed Detectors in hand, ready to test Simulate expected bandpasses Simulate photo-z signals

13. F. William High21 August 2006Clusters@LPPC 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

14. F. William High21 August 2006Clusters@LPPC PISCO: Collaboration Christopher Stubbs Tony Stark (SAO) John Geary (CfA) James Battat (LPPC) Ned Henry (LPPC) SPT: John Carlstrom (Chicago), Joe Mohr (Illinois), …

15. F. William High21 August 2006Clusters@LPPC Constant Cosmological Constant? Ultimate goal with BCS and PISCO: Ultimate goal with BCS and PISCO: measure whether dark energy is a constant vacuum energy Dark (vacuum) energy equation of state parameter w = p/ρ Matter δ evolves as: Hubble parameter: Dark energy Dark energy eqn of state parameter

16. F. William High21 August 2006Clusters@LPPC 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, … BCSPISCO