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Cosmic X-ray Background with Swift/BAT: un update (and some new results)

Cosmic X-ray Background with Swift/BAT: un update (and some new results). M. Ajello (MPE-Garching) with G.Sato, J. Greiner, G. Hasinger, G. Kanbach, A. Strong, N. Gehrels, J. Tueller, C. Markwardt. Submitted on Apr. 2nd. Gilli et al. 2007. CXB problem.

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Cosmic X-ray Background with Swift/BAT: un update (and some new results)

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  1. Cosmic X-ray Background with Swift/BAT: un update (and some new results) M. Ajello (MPE-Garching) with G.Sato, J. Greiner, G. Hasinger, G. Kanbach, A. Strong, N. Gehrels, J. Tueller, C. Markwardt Submitted on Apr. 2nd

  2. Gilli et al. 2007 CXB problem • HEAO-1 CXB: wrong in normalization, in shape or in both ? M. Ajello

  3. ON ON-OFF OFF CXB Measurement via Occultation On - Off  ( CXB - Earth) M. Ajello

  4. The ON-OFF ‘difference’ spectrum BAT detects modulation up to 200 keV at high significance Earth albedo dominates above 100 keV Method: fit in Xspec with CXB -albedo -> spectral templates assumed M. Ajello

  5. Results: CXB spectrum • BAT CXB extends up to 200 keV • BAT finds CXB is 8% larger than HEAO-1 M. Ajello

  6. Occultation Background fitting Results 2nd measurement M. Ajello

  7. Moretti et al. in preparation New Results from Swift/XRT!! • XRT measurement uses: • GRB follow-up observation • 1 month of closed-camera data • Several Crab observations to assess stray light M. Ajello

  8. BAT Clusters : Poster H. 1 M. Ajello

  9. Open Question • Radio Halos prove that relativistic electrons exist in the ICM(Kempner&Sarazin 01,Govoni et al 01, Thierbach et al 03) • EUV and soft excesses support this view (e.g. Bonamente 03-05-07, Nevalainen 03, Werner et al 07) Is there any non-thermal X-ray component? Yes: (e.gFusco-Femiano et al 99-03-04, Rephaeli 01-02, Gruber&Rephaeli 02, Nevalainen et al 01-04, Eckert et al 07, Lutovinov et al 08) No: (e.g Molendi&De Grandi, De Grandi&Molendi 99, Revnivtsev 04, Rossetti&Molendi 04-07, Ota et al 08) M. Ajello

  10. BAT sampleAjello, Rebusco, Cappelluti, ApJ submitted, May 2nd (www.mpe.mpg.de/~majello/ARC08.pdf) • 10 Clusters detected above 15 keV (all sky, out of 450 sources) • BAT does not provide spatial information (i.e. all clusters are point-like ….) • Use Chandra/XMM/XRT data in order to constrain non-thermal processes • What do we find ? …. M. Ajello

  11. NT component, finally! Perseus Abell 0754 M. Ajello

  12. NT component, finally! Too Early! Only AGN….. Perseus Abell 0754 M. Ajello

  13. Indeed… Sy2 @ z=0.3 Credits : A. Rau Henry+04 M. Ajello

  14. Abell 2319 The rest of the clusters • Consistent with pure thermal emission • Derive upper limit in the 50-100 keV band M. Ajello

  15. Comparison with previous detections M. Ajello

  16. Stacking analysis • Average of 8 spectra • Sensitivity pushed a factor 3 (10x exposure) • Still no NT emission • F50-100<1.9 x 10-12 cgs M. Ajello

  17. BAT BAT + XMM XMM XRT XMM XMM Chandra XMM What do we learn ? • Relativistic (GeV) e- can upscatter CMB photons viaInverse Compton (e.g. Rephaeli+79, Sarazin+99) • At the current fluxes, very low B : no equipartition (?) (e.g. Harris&Romanishin 74) M. Ajello

  18. N S-1.4 First source count and luminosity function (>15 keV) • BAT Clusters contribute only ~0.1% to the CXB, but they are ~5% wrt AGN • Good agreement with ROSAT(Jones+98, Boehringer+01) • Good agreement with ROSAT(Boehringer+02) M. Ajello

  19. Conclusions • BAT is a fantastic surveying instrument • Many exciting results on AGN, Clusters, etc. • Swift (BAT and XRT) show HEAO-1 CXB wrong in shape (?!) Good agreement with INTEGRAL • BAT clusters show no non-thermal components (agreement with independent analysis of T. Okajima+08) M. Ajello

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