z = 1.22 Red-Sequence Selected Clusters at 1 < z < 2 in the Spitzer SWIRE Survey Supervisor: Howard Yee Collaborators: Gillian Wilson Mark Lacy Henk Hoekstra Collaborators: Gillian Wilson Mark Lacy Henk Hoekstra Adam Muzzin University of Toronto Adam Muzzin University of Toronto z ~ 1.6 i,z,IRAC1

The cluster 3.6 micron luminosity function Redshift evolution of M * Rejected - low-z Two projects using the Red-Sequence Technique + Spitzer Spitzer First Look Survey: 120 Clusters z < 1 Rejected - low-z The MIR Butcher-Oemler Effect? Rejected - low-z

Spitzer SWIRE Survey: Clusters at 1 < z < 2

Current sample of spectroscopically confirmed galaxy clusters: Low-zMid-zHigh-z Cluster “Desert” Lyman-break Proto-clusters z < < z < < z < < z < < z < 6.5 ~ 1000’s~ 100’s~10’s0 Filling in here is crucial for understanding the full evolutionary history of cluster galaxies 1 Why do we need to find clusters at 1 < z < 2?

How to find these clusters? 1. Sunyaev - Zeldovich Effect - SPT, APEX 2. Photometric Redshifts - IRAC SS, UKIDSS 3. Red-Sequence Technique - US! All will work very well - 2 filter RS technique is fast, and observationally efficient

z= 0.0 z = 0.0 z= 1.0 z = 1.0 z= 1.5 z = 1.5 z= 2.0 z = 2.0 Cannot just go deeper with the RCS - We need to change filters RCS goes to z ~ 1.4

Skeptic: Will the RS-technique work at z > 1.4? Lots of evidence that would suggest: YES! Do clusters have a red-sequence at > 1.4? Steidel et al. (2005): Red Galaxies in a z = 2.3 Proto- Cluster

1.Deep, Wide-field IR imaging: Spitzer SWIRE Survey-50 deg 2 1.Deep, Wide-field IR imaging: Spitzer SWIRE Survey-50 deg 2 Now we are convinced clusters will have red- sequences at high-z, we need: 2. Deep optical z-band imaging

SWIRE/CFHTLS, XMM-LSS field Luckily there are two, overlapping public datasets which allow us to test this: SWIRE, and CFHTLS 6 degree 2 of overlapping data

We recover 8/9 X-ray clusters z > 0.35 from XMM- LSS How do we know we are finding real clusters? Red-Sequence photo-z’s are excellent: Δz < 0.1

z phot = z spec = z phot = z spec = 0.344

While we are here.... z phot = z spec = z phot = z spec = 0.429

z phot = z spec = z phot = z spec = 0.614

Examples of cluster candidates 1.2 < z < 1.85 Now you are totally convinced that this will work:

z phot = 1.225

z phot = 1.33

z phot = 1.475

z phot = 1.75

z phot = 1.85

Future Plans - Discovery Phase: 1. Gemini Project: Photometric Redshifts from ugrizJK+IRAC Gemini Project: Photometric Redshifts from ugrizJK+IRAC Image remaining SWIRE fields (40 deg 2 ) in z-band: ~500 clusters 1 < z < 2 3. Image remaining SWIRE fields (40 deg 2 ) in z-band: ~500 clusters 1 < z < 2 2. Spectroscopy of best candidates: confirmation+populations (expensive - redshift desert) 2. Spectroscopy of best candidates: confirmation+populations (expensive - redshift desert) Summary: ~70 cluster candidates 1 < z < 1.85 in 6 deg 2