1. X-Ray Observations of RCS Clusters at High Redshift
Erica Ellingson, U. Colorado
Amalia Hicks, U. Colorado/ U. Virginia
Mark Bautz, MIT
Henk Hoekstra (U. Victoria)
Mike Gladders, Carnegie Obs.
Howard Yee, U. Toronto

2. The RCS Surveys
Review by H. Yee earlier today: optically selected clusters via their red sequence
RCS-1; 90 square degrees (completed)
RCS-2: 1000 square degrees
Z ~ 1
Still needed: calibration of cluster mass estimates for optically selected clusters

3. RCS Chandra Observations
Chosen from the sample: 9 clusters (now 12)
(0.64) 0.75< z< 1.1
Some initial emphasis on the most massive, lensing systems from the first available RCS catalogs; sample is becoming representative of rich systems
ACIS exposures: (10) 30-90Ksec

4. Optical/Chandra Observations
Z=0.78
Z=0.64

5. 8 out of 9 detected with > 5 (2112-6326 at zph=1.1 is 2-3)
3 additional cluster detections on the way
(final data arrived this week)

6. 20ksec first exposure
(more just arrived):
Three new detections:
z ~

7. “Low Redshift” Comparisons
14 X-Ray selected CNOC (EMSS + Abell 2390)
0.17 < z < 0.55
Well determined masses via dynamics, lensing, Xrays
(ROSAT +Chandra)
25% scatter
XXXX vdMarel
Carlberg, Yee & Ellingson 1997
van der Marel et al. 2000
Lewis et al. 1999
Hicks et al. 2005

8. Lensing Masses for CNOC
Weak lensing comparisons at z=
(with Henk Hoekstra)
Slight systematic mass overestimate (10%) for weak lensing masses

9. Calibrating Optical Richness with X-ray properties
Initial mass estimator for RCS is the optical richness from the survey data: Bgc
CNOC: Good agreement with expected relationships:
Bgc vs. ,Lx,Tx,M200
Yee & Ellingson 2003, updated for Chandra by Hicks, et al., 2005
Bgc well determined as a possible mass calibrator:
dynamics, lensing
Black: weak lensing shear composites (Hoekstra)
Red: CNOC cluster dynamics

10. RCS: Lx-Bgc RCS clusters are under-luminous for their optical richness
See also:
Donahue et al. 99,
Gilbank, 2004
Lubin et al., 2004 …
XXX
Sope=?
L2500
CNOC, CF corrected : diamonds
RCS: squares

11. Tx-Bgc Temperatures show general agreement with lower-z X-ray samples
Slightly systematically lower temperature for their optical richnesses
Outlier: superposition of groups in small z range (e.g., Gilbank’s talk,
also Gonzales’ supergroup?):
predicted to be ~5% of RCS?
Note: 3 clusters NOT plotted
Maybe one more in sample of 12
Diamonds= CNOC
Squares = 6 RCS clusters with
enough signal to measure Tx

12. Lx-Tx
RCS: clusters underluminous for expected Tx? Large uncertainties…
Solid: slope=2.2
Dotted = 2.0
Dashed= best fit slope 4+/- 2
See also Lubin, et al., 2004
0439 rejoins the sample
clear we need more and better Tx’s, especially for richer clusters we’ve discovered as the sample has been completed. CNOC slope
Combined: 4+- 2,
CNOC: diamonds
RCS: squares

13. Redshift Evolution of Optical/X-ray mass estimates?
Tx-Bgc is scaled by M200-Bgc-Tx relation to reduce to a mass ratio
Evolution seen in
X-ray-selected CNOC sample at z < 0.6?
Mass ~ Bgc (1+z)
= /- 0.5
Why? LF evolves differently- faster? Nope…
Spatial distribution of galaxies such that Bgc measures larger fraction of galaxies
OR evolution of optically-selected clusters- most likely
Consistent with self-calibrating
model for RCS (Majumdar, later today)

14. SZ detections BIMA/OVRO observations from Kyle Dawson &
J. Carlstrom’s group
6 RCS clusters detected
Agreement with X-ray results for Mtot and Mgas requires factor of 2 variation in gas fractions, consistent with lowered X-ray luminosities
Gas fraction on the cores may explain some of it?

15. AGN in Clusters
CNOC: excess of X-ray point sources in a few clusters….
Overall, no strong excess
Straight line = expected background
Histo = 2-8 keV point sources
Ellingson et al. 2005

16. RCS: analysis just beginning
RCS , z=0.78- regular, lensing cluster, possible small cooling core
Excess of sources just inside the virial radius (see also Rudman & Ebeling 2005)
Significant energy ejection by AGN?
(e.g., talk by Donahue)
Need to see if this is ubiquitous for all RCS clusters…

17. Conclusions
RCS Clusters at z > 0.75 are X-ray sources- all detected
“Contamination” by “super group” structures at ~zcluster or 2 out of 12, also X-ray sources
X-ray luminosities and gas fractions within R2500 scatter systematically low. Lx-Tx is not unreasonable- ?steeper? (large error bars!). Virialization of all components is required to produce uniform X-ray/optical relations.
Tx-richness relation shows that red galaxies reliably indicate mass (not necessarily virialized). Relation shows some evolution, consistent with self-calibrating N(M,z) models.
Further comparisons with dynamics, lensing (HST) , IR luminosity (Spitzer) are under way!
Nothing terrifically surprising
Contamination: Tx is factor of 2 lower than exected from Bgc