# Presentation: 818891

## XCSCurrent status and Expectations for Parameter Estimation

-      C.A. Collins (Liverpool John Moores University)	     R.G. Mann (IfA, Edinburgh)
-      M. Davidson (IfA, Edinburgh)		     R.C. Nichol (Carnegie Mellon University)
-      M.J. Hilton (Liverpool John Moores University)	     A.K. Romer (Carnegie Mellon University)
-      S.T. Kay (University of Sussex)		     K. Sabirli (Carnegie Mellon University)
-      K.R Land (Imperial College)		     P.T.P. Viana (University of Porto)
-      A.R. Liddle (University of Sussex)		     M.J. West (University of Hawaii)

## X-ray Cluster Survey

- X-ray Cluster Survey
- 	Search for galaxy clusters in ≈60 deg2 of non-overlapping sky imaged by
*	**XMM-Newton* per year, leading to a ≈500 deg2 catalogue by ≈2010 with
- 	an effective bolometric flux limit around 2.2x10-14 ergs-1 cm-2, or about
- 	0.9x10-14 ergs-1 cm-2  in the [0.5,2] keV band

- XMMU J183225.4-103645
- 5.8 keV, z=0.124
- Nevalainen et al. 2001

-  if 0=0.3, =0.7 then on the order of 3000 clusters
-  detections are expected (T>2 keV, with ~10% at z>1)

##   if 0=0.3, =0.7 then around 440 clusters with T>4 keV (27% at z>1) are 

-   if 0=0.3, =0.7 then around 440 clusters with T>4 keV (27% at z>1) are
-   expected to be detected (6), with about 50% having their temperatures
-   estimated with less than 20% error (1) from the serendipitous data alone

- Romer et al. 2001

##    XCS possible uses

-    Galaxy clusters as cosmological probes - 8, Ω0, Ω [Ωw, w]
-    (number density evolution, baryon fraction, H(z) from the
-    Sunyaev-Zel’dovich effect - X-ray/sub-mm joint analysis)
-    Evolution of intracluster gas properties as a probe
-    to the physics of cluster formation and evolution
-    Evolution of the properties of cluster galaxies as a window
-    on the processes responsible for galaxy formation and evolution
-    Exploit galaxy clusters as gravitational lenses of ultra-high redshift objects

-    XCS objective
-    Construction of a large catalogue of galaxy clusters extending beyond z=1
-    with a well-defined (though not necessarily simple!) selection function    [c.f. the EMSS sample which has almost 15 years of active service]

##   Current Status

-   Current Status
-    *XMM-Newton* observations in excess of 3400 have been performed as
-    of end of 2003, with about 2/3 already in the public domain, in total
-    around 300 deg2 of non-overlapping sky presently observed of which
-    140 deg2 are already being searched for serendipitous XCS clusters
-    Automated download and data analysis pipeline in place, based
-    on SAS - Science Analysis System, generating a continuously
-    updated source list from data that falls on the public domain
-    [poster by K. Sabirli for more details]
-    Wavelet based software for the identification and
-    characterization of extended sources under development,
-    with ongoing tests indicating that even some of the most
-    distant X-ray clusters known are flagged as being extended
-    Around 20 candidate XCS clusters have been optically confirmed
-    through cross-correlation with SDSS data, while for nearly 30 others
-    imaging data acquired with the Hawaii 2.2m telescope is being analyzed

## Poster by M. Davidson for more details

- Poster by M. Davidson for more details

- z=0.78
- MS 1137.5+6625

- SDSS

- XMM-Newton

## Based on data from 3 deg2 - poster by M. Davidson for more details

- Based on data from 3 deg2 - poster by M. Davidson for more details

- HELLAS2XMM
- Baldi et al. 2002

- HDF-N
- Miyaji et al. 2003

##    Likelihood analysis

-    Likelihood analysis
- Methodology:
- 1)   1000 mock XCS catalogues of galaxy clusters with Tx > 2 keV
-       and z < 2, and high enough X-ray luminosities for their X-ray
-       temperatures to be accurately estimated solely from the XCS
-       data, were generated by randomly drawing from a Poisson
-       distribution with mean Nxcs(Tx,z) as expected for the
-       assumed fiducial model with 8=0.8, Ω0=0.3, Ω=0.7
- 2)   a likelihood method was then applied to each mock XCS
-       catalogue to find the most probable underlying 8, Ω0, Ω
- The Jenkins et al. 2001 mass function was used. It was also assumed
- that the Lx - Tx relation does not evolve with *z* and that the M500 - Tx
- relation (Finoguenov, Reiprich & Böhringer 2001) evolves in a self-similar way.
- Further, it was not taken into consideration the possibility of scatter
- in these relations, or errors in the measurements of Lx, Tx and *z*.

##     XCS joint estimation of 8, Ω0, Ω 

-     XCS joint estimation of 8, Ω0, Ω
-     to within 10 per cent (5 per  cent
-     for 8) of their true values at the
-     95 per cent confidence level
-     Preliminary results indicate that if
-     the present-day normalization of the
-     M500 - Tx relation is to be recovered
-     from the XCS data, then there will be
-     a substantial degradation in the above
-     accuracy, particularly in the case of 8

##      We have found that in effect any galaxy cluster with a bolometric flux 

-      We have found that in effect any galaxy cluster with a bolometric flux
-    exceeding a value of about 1.1x10-13 ergs-1 cm-2, will have its X-ray
-    temperature accurately measured based only on the analysis of XCS
-    data. That is to say that any galaxy cluster survey, over an equivalent
-    area of sky, that ensures at least 1000 cluster photon counts for every
-    cluster with bolometric flux in excess of the above value, will yield
-    constraints on cosmological parameters, as well as on the present-day
-    cluster X-ray relations and their redshift evolution, very similar to those
-    that will be obtained by XCS.
-      We have also found that a similar level of constraint can be achieved
-    solely from a 6000 deg2 galaxy cluster survey, based just on the
-    evolution of cluster number counts, only if it ensures at least 1000
-    cluster photon counts for every cluster with bolometric flux in excess
-    of about 10-12 ergs-1 cm-2. This translates into a cluster detection
-    bolometric flux limit for such a survey of 10-13 ergs-1 cm-2 (assuming
-    that at least 100 cluster photon counts are necessary for a detection).

##   Parallel ongoing and future work

-   Parallel ongoing and future work
-    Development of neural network analysis software for redshift
-    estimation based on emission-line identification in cluster
-    X-ray spectra [see poster by K. Sabirli for more details]
-    Analysis of the viability of using cluster X-ray observables to
-    pre-select the most massive high-z clusters for subsequent
-    optical identification and redshift measurement
-    Bremsstrahlung emission
-    lneT-1/2e-h/kT    =>  Tapp=T/(1+z)

## 	in both the Lx-Tx relation and Tx estimation included 

- 	0.6<z<0.9  orange	       z>0.9  red

- 	Simulation of X-ray cluster observables with uncertainties
- 	in both the Lx-Tx relation and Tx estimation included

- 260

- 120

- Liddle et al. 2001

##   Parallel ongoing and future work

-   Parallel ongoing and future work
-    Development of Markov Chain Monte Carlo simulation software
-    to explore in a time efficient manner the full parameter space
-    that results from using the XCS data to simultaneously constrain
-    both the present-day normalization and redshift evolution of
-    relations between cluster X-ray observables and also the most
-    important cosmological parameters 8, Ω0, Ω [Ωw, w]
-    XCS selection function determination using XMM-Newton cluster
-    data as well as realistic cluster images from hydrodynamic N-body
-    simulations.To be correctly derived, the instrument sensitivity, i.e.
-    the cluster X-ray flux detectability limit as a function of X-ray
-    temperature, luminosity and redshift, needs to be characterized.
-    Such sensitivity will depend both on cluster X-ray properties, like
-    temperature, profile, shape, orientation and metalicity, as well as
-    on cosmological parameters and on the way the data is acquired
-    and reduced: integration time; cosmic and particle background
-    noise; vignetting corrections; cluster ID algorithm.