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Sergio Campana On behalf of the survey WG

Cluster of galaxies and large area survey. Sergio Campana On behalf of the survey WG INAF - Osservatorio Astronomico di Brera/INAF - Via Bianchi 46 – 23807 Merate (Lc) – Italy. Outline. Prospects for a large area X-ray survey.

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Sergio Campana On behalf of the survey WG

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  1. Cluster of galaxies and large area survey Sergio Campana On behalf of the survey WG INAF - Osservatorio Astronomico di Brera/INAF - Via Bianchi 46 – 23807 Merate (Lc) – Italy

  2. Outline • Prospects for a large area X-ray survey Mainly based on WAXS/WFXT and Panoram-X proposals as well as NASA white papers (Haiman et al. 2005 and Vikhlinin et al. 2005) and final JDEM proposal (Bautz et al. 2006). • Important news: • NASA did not accept JDEM proposal (this is good in some respects) • concerns on calibration of systematic uncertainties through self- calibrations • existence of different cluster populations (e.g. sub-luminous population) or AGNs in the cluster center (20-30% contamination)

  3. Why is the universe expansion accelerating? JDEM driver What is DE made of? (73% of our universe is made of DE!)

  4. DE Probes Now Future CMB WMAP Planck Supernovae HST SNAP Clusters of galaxies X-ray satellites ?? Cluster of galaxies No dedicated project Dedicated survey?

  5. Cluster power spectrum and X-ray luminosity function (Schuecker et al. 2003; Boehringer 2006) JDEM APPROACH Brute-force self-calibration Complementary approaches to sensibly reduce systematic uncertainties (Mohr’s et al. papers) Evolution of the cluster temperature (Henry 2004) Constancy of the cluster baryon fraction (Allen et al. 2004) Evolution of the cluster gas mass (Vikhlinin et al. 2003; 2006)

  6. JDEM Cluster Survey 105 clusters Cluster survey in context

  7. Possible synergy with GRB studies • Ghirlanda’s and Firmani’s relations are tight correlations • Nice and complementary use of tools with the same instrument • but…: • if we are worried by criticisms a-la JDEM, stronger criticisms on the cosmological ues of these relations have been put forward (e.g. Friedman & Bloom) • for the Ghirlanda’s relation the time of the jet-break is critical but this time is shown to be very difficult to be determined in the Swift era (breaks observed in X-rays and not in the optical and viceversa) • for the Firmani’s relation the variability parameter is critical and heavily dependent on background and light curve filtering

  8. Possible (and necessary) synergies with other surveys Need for an optical follow-up (many in preparation, should not be a problem) SZ survey? South Galactic pole region? Weak Lensing survey? (We have to think not only to clusters, i.e. IR surveys, radio surveys etc. to identify the survey region)

  9. Life after JDEM More difficult to have a (X-ray) cluster-based DE explorer mission. (In case) we have to better describe the self-calibration process and assess the contamination of AGN in cluster cores But … lack of a “reasonable” X-ray survey in the near future

  10. Lack of a large area (cluster) survey

  11. A possible competitor eROSITA (a.k.a. ROSITA – ABRIXAS) on board Spectrum RG 7 mirrors (nickel, 0.2-0.9 mm thickness) and 7 detectors (CCD-pn) HEW < 15 arcsec (on-axis) – HEW < 25 arcsec (mean FOV) Effective area 2471 cm2 (60x7=420 kg) GRASP = 800 Field of view 41x41 arcmin2 = 0.47 deg2 Mean vignetting 0.7 Survey duration 4 yr with 90% efficiency Survey sensitivity (0.5-2 keV) 9x10-15 cgs (point) 4x10-14 cgs (extended) Main emphasis on DE – cluster survey – obscured AGNs

  12. 7 mirrors (nickel, 0.2-0.9 mm thickness) and 7 detectors (CCD-pn) HEW < 15 arcsec (on-axis) – HEW < 25 arcsec (mean FOV) Collecting area 2471 cm2 (60x7=420 kg) GRASP = 800 Field of view 41x41 arcmin2 x 7 = 0.47 deg2 Mean vignetting 0.7 Survey duration 4 yr with 90% efficiency(?) All-sky Survey sensitivity (0.5-2 keV) 9x10-15 cgs (point) 4x10-14 cgs (extended) eROSITA HEW < 10-15 arcsec (mean FOV) Collecting area 1350 cm2 (TBD kg) GRASP = 1900 Field of view 1.4 deg2 Mean vignetting 0.7 Survey duration 1 yr with 70% efficiency eROSITA survey can be carried out in  1-2 yr (a factor of 2-4 better) ESTREMO

  13. Simulation of a 2,000 s, 1.7 1.7 square degrees field observation. There are ten clusters with fluxes ranging in 0.59  10-13 erg s-1 cm-2 (#1-#10). Note that all background points in the image correspond to sources. All clusters are detected as extended with high significance. Survey simulated image

  14. Point-source limit Side products: X-ray background Cosmic web AGN studies Starts in our Galaxy Cataclismic variables

  15. What do we need? Practice Which survey strategy? (in 1 yr) All-sky? Smaller and deeper area? Trade-off study between large area (massive clusters) and cluster properties (mainly T, need photons) to limit systematics i.e. is there a need to have 100,000 clusters or it is better to have 10,000 well-characterized clusters? Not easy! Not be carried out in depth yet SUGGESTION Area : 10,000 deg2 (2200 s expos.) Extended source Det Lim : 30 counts Allocated time : 12 months (spread over MLF) Flux limit for ext. sources : 5 x10-14 erg cm-2 s-1 2 telescope CCD: detection Microc: z for the brightest

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