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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

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

Gilli et al. 2007

CXB problem
  • HEAO-1 CXB: wrong in normalization, in shape or in both ?

M. Ajello

cxb measurement via occultation

ON

ON-OFF

OFF

CXB Measurement via Occultation

On - Off  ( CXB - Earth)

M. Ajello

the on off difference spectrum
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
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

Results 2nd measurement

M. Ajello

new results from swift xrt

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

open question
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

bat sample ajello rebusco cappelluti apj submitted may 2nd www mpe mpg de majello arc08 pdf
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

nt component finally
NT component, finally!

Perseus

Abell 0754

M. Ajello

nt component finally1
NT component, finally!

Too Early! Only AGN…..

Perseus

Abell 0754

M. Ajello

indeed
Indeed…

Sy2 @ z=0.3

Credits : A. Rau

Henry+04

M. Ajello

the rest of the clusters

Abell 2319

The rest of the clusters
  • Consistent with pure thermal emission
  • Derive upper limit in the 50-100 keV band

M. Ajello

stacking analysis
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

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

first source count and luminosity function 15 kev

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

conclusions
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