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

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

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

er

of

Nu

mb

er

of

clu

ste

rsc

lus

ters

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

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

21 August 2006 Clusters@LPPC F. William High

Two Challenges

Mass of clusters?

Solution: BCSBCS

Distance to clusters?

Solution: PISCOPISCO

Observable:

Probability:

Matter evolution:

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)

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

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

21 August 2006 Clusters@LPPC F. William High

PISCO: Design

Ideal broadband photometer!Ideal broadband photometer!

Dichroic beamsplittersDichroic beamsplitters define bandpassesdefine bandpasses

21 August 2006 Clusters@LPPC F. William High

PISCO: Design

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