M. Ajello (MPE-Garching) 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

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

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

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

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

Results 2nd measurement Occultation Background fitting M. Ajello

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 Moretti et al. in preparation Stray-light well assessed M. Ajello

BAT Clusters : Poster H. 1 M. Ajello

Is there any non-thermal X-ray component? 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.g Fusco-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

BAT sample Ajello, Rebusco, Cappelluti, ApJ submitted, May 2nd (www BAT sample Ajello, 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

NT component, finally! Perseus Abell 0754 M. Ajello

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

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

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

Comparison with previous detections CLUSTER Perseus A 3266 A 0754 A 3571 A 2029 A 2142 Triangulum A. Ophiucus A 2319 INSTRUMENT BeppoSAX -- INTEGRAL/BeppoSAX RXTE AGREE? AGN AGN! M. Ajello

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

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

First source count and luminosity function (>15 keV) N S-1.4 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

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