The XMM Distant Cluster Project: Survey limits and Pilot Survey Georg Lamer A. Schwope, V. Hambaryan, M. Godolt (AIP) H. Böhringer, R. Fassbender, P. Schücker, J. Santos (MPE) C. Mullis (U Michigan), P. Rosati (ESO)

1.Extended source detection and survey sensitivity 2.X-ray redshifts 3. First results from pilot survey

Rosati et al Motivations for a z>1 cluster survey Existing samples mostly at z<1 Significance for cosmology: –Evolution of cluster luminosity function puts strong constraints on  m Mullis et al. 2003

Motivations for a z>1 cluster survey Existing samples mostly at z<1 Significance for cosmology: –Evolution of cluster luminosity function puts strong constraints on  m Allen et al High z samples needed for the investigation of –the cluster galaxy evolution –the evolution of the intracluster medium –Constraints on dark energy by measuring distances via the cluster gas fraction (cf talk by Stefano Ettori on caveats)

X-ray surveys for clusters of galaxies XMM serendipity survey Rosati et al. 2002

XMM serendipity survey ~4000 archived observations 0.15 deg 2 FOV High sensitivity erg/(cm 2 s) resolve even most distant clusters Almost all extended sources are clusters

Source detection pipeline EPIC images eexpmap exposure maps Standard XMM-SAS detection tasks Similar setup as for 2XMM catalogue eboxdetect esplinemap background maps eboxdetect emldetect PSF fiiting

Source detection pipeline emldetect: Fitting PSF folded with King profile

Verification of survey limits Simulation of XMM EPIC data: –Simulate 100 source lists with AGN logN-logS (Hasinger & Brandt 2005) + cluster logN – logS (Rosati et al. 1998) –Create simulated EPIC images in 3 x 5 energy bands (typical background, 20 ksec exposure). Run source detection pipeline on fake data sets.

Verification of survey limits

Detected fraction: f= Spurious fraction (before visual screening)

X-ray redshifts Possibility of measuring redshifts from X-ray spectra? Extracted spectra of 90 clusters with > 500 counts, calculating grid of MEKAL models in T-z plane (Master thesis M. Godolt). Mekal redshift=0.8 kT= 4.0

X-ray redshifts Determined 17 redshifts (mostly low T z< 0.5)

X-ray redshifts Newly discovered z=0.8: Subaru I-band

Pilot cluster survey Survey area: 9 deg 2 at sensitivity 7x cgs Best sensitivity: cgs Detected 155 extended sources Optical follow up in ESO P72 / P73 (2003/2004)

Optical follow up observations Select high redshift cluster candidates using DSS images –Eliminate non-cluster identifications –Select DSS blank fields for R + z band imaging with VLT FORS2 VLT imaging in R + z bands (47 candidates) –Estimate photometric redshifts Spectroscopic confirmation (VLT FORS 2)

Selecting blank DSS fields

EPIC DSS2

VLT imaging Imaging observations with FORS 2: R and z bands R lim > 24.5, z lim > 23 m Determine R-z colours  cluster red sequence  redshift estimate. z~1.2

Pilot survey: Results Photometric (R-z) redshifts 10

RzK composite

XMMU J z = 1.39 Mullis et al. 2005

XMMU J fact sheet f X = 3.6 x erg/(cm 2 s) L X = 3 x h erg/s (0.5 – 2.0 keV) kT = keV (280 photons)  M ~ 5 x M sun Cluster red sequence: R – z ~ redshifts between 1.38 and 1.40: = Velocity dispersion: km/s Follow-up observations with Chandra, XMM, Spitzer, HST...

Conclusions & Outlook Survey sensitivity well described by simulations. Limited possibility to obtain redshifts from XMM spectra. Pilot survey demonstrated efficient strategy to find distant clusters ~ 1/4 of new XMM clusters at z > 0.5 ~ 1/4 of these have z > 1.0 XMM : X-ray luminous cluster at z=1.39 Next goal: sample of 30 clusters at z >1