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Sergio Campana

Cluster of galaxies and large area survey & Wide-field X-ray telescopes. Sergio Campana INAF - Osservatorio Astronomico di Brera/INAF - Via Bianchi 46 – 23807 Merate (Lc) – Italy. Outline. Dark energy probe: needs for a large area survey

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Sergio Campana

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  1. Cluster of galaxies and large area survey & Wide-field X-ray telescopes Sergio Campana INAF - Osservatorio Astronomico di Brera/INAF - Via Bianchi 46 – 23807 Merate (Lc) – Italy

  2. Outline • Dark energy probe: needs for a large area survey • Wide-field X-ray polynomial optics for imaging applications: short review of the concept Mainly based on Panoram-X proposal and NASA white papers (Haiman et al. 2005 and Vikhlinin et al. 2005) and final JDEM proposal (Bautz et al. 2006). but… I am not an expert in clusters of galaxies and large scale structures I am not an expert in mirror manufacturing … so I will try to be short

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

  4. Probes Now Future CMB WMAP Planck Supernovae HST SNAP Clusters of galaxies X-ray satellites ?? Cluster of galaxies Dedicated survey?

  5. Cluster power spectrum and X-ray luminosity function (Schuecker et al. 2003; Boehringer 2006) Evolution of the cluster temperature (Henry 2004) COMPLEMENTARY APPROACHES Constan-cy of the cluster baryon fraction (Allen et al. 2004) Evolution of the cluster gas mass (Vikhlinin et al. 2003; 2006)

  6. Cluster Survey 105 clusters Need to study the brightest fraction of clusters to calibrate relations Constrain the equation of state of Dark Energy, (i.e. understand what is it!) w(z)=w0 + wa z/(1+z) Better than high-z SNe or weak lensing surveys

  7. Cluster survey in context

  8. 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

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

  10. What do we need? Theory

  11. What do we need? Practice Field of view : 1.4 square degrees Orbit efficiency : 70% Vignetting efficiency : 70% Survey area : 10-20,000 square degrees (slowly drifting satellite) Extended source detection : 30-50 counts Allocated time : 9-12 months Flux limit for ext. sources : 2-5 x10-14 erg cm-2 s-1 7-14,000 pointings MINIMAL REQUIRMENTS Area : 10,000 square degrees Extended source detection : 30 counts Allocated time : 9 months Flux limit for ext. sources : 5 x10-14 erg cm-2 s-1 Need 1,825 cm2

  12. What about angular resolution Concerning clusters of galaxies 15 arcsec HEW (over the entire field of view) are enough …but for survey purposes the lower the better (Goal: 5 arcsec HEW over the entire field of view) How can we obtain these features?

  13. X-ray optics with polynomial profile • Mirrors are usually built in the Wolter I (paraboloid-hyperboloid) configuration which provides, in principle, perfect on-axis images. • This design exhibits no spherical aberration on-axis but suffers from field curvature, coma and astigmatism, which make the angular resolution to degrade rapidly with increasing off-axis angles. • More general mirror designs than Wolter's exist in which the primary and secondary mirror surfaces are expanded as a power series. • These polynomial solutions are well suited for optimization purposes, which may be used to increase the angular resolution at large off-axis positions, degrading the on-axis performances (Burrows, Burgh and Giacconi1992) • A trade-off of the whole optics assembly of a wide-field telescope can further on increase the imaging capabilities off-axis of wide-field polynomial optics The wide-field polynomial optics concept was extensively studied as a part of the WFXT mission concept (OAB, CfA, Univ. of Leicester)

  14. Some historical remarks on WFXT-like missions • 1992, Burrows, Burg and Giacconi investgate the possibility of using polinomial mirror configurations to get X-ray optics with a corrected PSF onto a large FOV • 1995: WFXT small satellite proposal to NASA (PI R. Burg, J. Hopkins Univ, CfA, OAB) • 1997-98: WFXT proposal and Phase A to ASI in the context of the small satellites program (PI G. Chincarini, OAB + large part of the Italian AE community, CfA, Leicester Univ.) • 2000: Panoram-X mission proposal to ESA in the context of the F2-F3 program • 2001: Conconi & Campana paper (A&A 2001) improving mirror design • 2003: ASTER-X concept (OAB in collaboration with NASA/GSFC) in view of the probe-Einstein program (never started), further mirror design improvement • 2005 NASA Call for white papers on Dark Energy exploration; two proposal based on the Panoram-X concept; also ESA mention in the Cosmic Vision booklet the need of a similar mission, merged into a single proposal DECS (PI Bautz/MIT – including OAB scientists).

  15. Tests @ Panter-MPE & Marshall XRF Citterio et al. 1999,SPIE 3766 198 WFXT (ASI feasibility study 1997-1998) – Polynomial mirrors WFXT (epoxy replication on SiC carrier) – Ø = 60 cm Focal Lenght = 300 cm HEW = 10 arcsec

  16. The Panoram-X mission • proposed to ESA in 2001 in the context of the F2-F3 Mission Program • in practice, it is the same WFXT concept scaled up in FL (3.5 vs. 3 m) and # of mirror shells (50 vs. 24) • SiC mirror shells with diameter ranging from 70 to 21 cm, total mirror height of 28 cm and max wall thickness= 1 mm. Predicted HEW of 10 arcsec over a field radius of 30 arcmin (including profile and integration errors) • X-ray camera made of an array of nine CCDs arranged in an inverted pyramid that matches the focal surface of the mirrors. Each device is a 600x600 pixel front side illuminated frame store with pixel size 40 m corresponding to 2.4 arcsec in the focal plane. Energy resolution provided by the CCDs is E/E 10% at 1.5 keV

  17. E = 1 keV Panoram-X Effective Area Aeff(average)*W = 600 cm2* (1.2o)2

  18. The ASTER-X (ASTronomical ExploreR for X-rays) mission • Study performed in view of a Probe-Einstein class mission (2003 year) under request of NASA/GSFC • Baseline: an X-ray telescope able to provide 1300 cm2 at 1.5 keV and 650 cm2 at 4 keV of effective area, with an angular resolution (HEW) better than 5 arcsec over a FOV of 30 arcmin • #2 mirror modules, 12 monolithic shells • Focal length 7 m • Max, Min diameters: 1020 - 690 mm • Max, Min height: 485 mm, 330 mm • The focal plane has a curvature radius of 280 mm • Wall thickness: 10 mm constant • if made in ZerodurTM423 Kg per module • if made in foamed SiC  a factor 3 less (at least!) Optical axis

  19. ASTER-X: theoretical performances of the design HEW of the order of ~3 arcsec on most of the FOV, reaching a value of ~5 arcsec at 30 arcmin off-axis On-axis effective area: 800 cm2 @1 keV/ module The reflecting coating is Ir + a Carbon overcoating to enhance the soft X-ray reflectivity

  20. ASTER-X off-axis vignetting Aeff(average) x V = 400 cm2 x (1.4o)2

  21. ASTER-X feasibility • Mirror shells twice longer than WFXT: it’s a much more favorable conditions to reduce slope errors • Focal length similar to that used for Chandra and XMM • Mass-to-area ratio just ~20 % than ROSAT if ZerodurTM is assumed Difference (rms) between Wolter I and polynomial profiles Typical rms surface values measured for ROSAT:  0.5 arcsec Adding 0”.5 rms value to our nominal polynomial profile, we find that the HEW values increase on average less than 1” and remain always below 5”.

  22. Possible implementation of a cluster survey mission based on the previous concepts Possible options: • ready-off-the-shelf & not (too) expensive mirror technology (XMM-like with refined design based on Ni) to meet the moderate angular requirement (15-25 arcsec HEW). • use of the same technology and input requirement of wide FOV high imaging mission (ASTER-X like based on ZERODUR, i.e. glass) to have a 5-10 arcsec HEW. To have an effective area of 1800 cm2 this implies a total mirror weight of  800 kg x Tsurvey/(9 months) • new technologies under study like slumped glass (HEW  5-10 arcsec andweight 250 T9 kg) or already proven SiC (HEW 10-20 arcsec and weight 200 T9 kg)

  23. Conclusions Theory: strongly constrain Dark Energy equation and deep survey of the AGN population Large area cluster survey >10,000 square degrees Effective area >1,800 cm2 and/or survey time > 9 months Mean HEW < 15 arcsec Caveats (to have 5 arcsec HEW) Ad hoc mirror assembly (mirrors with different lenghts) Ad hoc focal plane assembly (inverted pyramid) Practice: feasible from the point of view of mirrors. Angular resolution depending on mirror weight

  24. My personal view • Microcalorimeters science: • WHIM absorption • WHIM emission • GRB • Superbursts • Type I X-ray bursts • CCD science: • Dark energy • Outskirts of clusters Science drives Vision Single telescope (1800 cm2 5-10” HEW) Small FOV microcalorimeter (< 5’x5’) CCDs around (> 30’x30’, possibly 40’x40’) Fast response and GRB/superburst location capabilities

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