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ULIRGs in hard X-ray: From XMM to Simbol X

ULIRGs in hard X-ray: From XMM to Simbol X. V. Braito. Review past X-ray observations of ULIRGs Open questions: relative contribution SB and AGN Need of observation above 10 keV. 1.ULI R Gs are predominantly powered by heavily d ust enshrouded AGN or circumnuclear SB ?.

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ULIRGs in hard X-ray: From XMM to Simbol X

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  1. ULIRGs in hard X-ray: From XMM to Simbol X V. Braito • Review past X-ray observations of ULIRGs • Open questions: relative contribution SB and AGN • Need of observation above 10 keV

  2. 1.ULIRGs are predominantly powered by heavily dust enshrouded AGN or circumnuclear SB? ULIRGs are a class of sources with LIR>1012L comparable to QSO luminosities. • ULIRGs have a space density comparable to QSO • All ULIRGs are invariably very dust and gas rich systems • Are the long sought QSO2 hidden in ULIRGs?

  3. 2. understanding role of mergers - SB and AGN activity - in the framework of AGN feedback A high fraction of ULIRGs are involved in interactions and mergers. These events provide the inflow of dust and gas toward the central region, which can fuel and obscure the SB and AGN. AGN and SB activity are frequently found together in ULIRGs ULIRGs as a tool to understand galaxies formation, connection between black hole growth and galaxy formation and evolution. • Energy budget in ULIRGs: what is the relative contribution of AGN and SB?

  4. ASCA, SAX, XMM, Chandra view of local ULIRGs • Aims 1-the hard X-ray less affected by the absorption then it is ideal to investigate the nature of the nuclear emission • 2- the presence of an obscured AGN in LIRGS and ULIRGs can be more frequent than estimated at other wavelengths (i.e. NGC 6240) XMM and Chandra surveys results: the majority are powered by SB; LX(2-10 keV)  1041-1042 ergs/s (Franceschini, Braito et al. 03, Ptak et al. 03, Teng et al. 05) Thermal emission with kT~0.7 keV is always present

  5. absorbed power law (AGN) ~1.7-2 or a flat power law (X-ray binaries) E1-e-E/Ec Ec=8 keV Thermal emission The SB-ULIRGs The hard X-ray emission detected with Chandra and XMM can be due to an hidden AGN or a population of X-ray binaries.

  6. SRF indicators from FIR to X-ray a correlation from low to high SFR and from low to high redshift X-ray/FIR correlation for local SB and SB-ULIRGs suggests that X-ray luminosity may be a SFR indicator (Ranalli et al. 03; Persic et al. 04, Grimm et al. 03) • uncertainty concerning the slope and normalization • AGN and SB activity are frequently found together in ULIRGs • The presence of highly obscured AGN cannot be ruled out To calibrate a SFR IR-X ray indicator is fundamental a direct measure of the intrinsic nuclear emission

  7. IRAS 19254-7245 Mrk 231 The AGN-ULIRGs • AGN in ULIRGs are obscured by large column density • Hard X-ray luminosity seems to be lower than typical QSO luminosity BUT • Due to the limited band pass for some ULIRGs the intrinsic AGN power is unknown Spectra presents several components: difficult to disentangle AGN and SB with limited band pass

  8. The AGN in IRAS 19254-7245:XMM and L band observations Strong reflected continuum plus a scattered power law, Fe line at E~6.4 keV (EW~1 keV). Observed L(2-10 keV)= 3x1042 erg/s (Braito et al. 03) Broad absorption feature at 3.4m indicative of heavily absorbed and high luminosity AGN (Risaliti et al. 03) If the source is Compton thick the hard X-ray luminosity could be L(2-10 keV)~1044 erg s-1  in QSO regime

  9. ~1.6 NH~1e22cm-2 IRAS19254-7245 Suzaku I Sey2 z=0.287 IRAS19254-7245 Compton thin no evidence of high NH; no Fe k line Fx (15-40keV)~ 3e-13erg cm-2 s-1 Confirm the XMM spectrum Hard continuum (~1.2); strong Fe line EW Fe~800eV)

  10. PIN minus NXB vs CXB model Background Ni line Courtesy of J. Reeves Flux 15-40 kev ~7e-12 cgs NH~5e24cm-2 Lx (2-10) ~1e44erg/s IRAS19254-7245 Suzaku IIHXD-pin preliminary results • Caveat: • CXB indirectly subtracted assuming the most recent model: uncertainties ~ 10% on its normalization • Contamination due to the large HXD FOV

  11. II case: no direct component (i.e. NH>1025cm-2) FX10-40 keV~1.2e-12cgs 100 ksec observation: I from Suzaku best fit What’s next: IRAS19254-7245 with SimbolX • High sensitivity will allow detection of faint obscured AGN • Spatial resolution: • Avoid possible contamination from nearby bright sources • Subtract local background ~5%; NH >1e25 LX ? Norm ~35% 6000 cts MPD 1400 CZT NH~3% ~1% LX~10-20%

  12. Fx (15-100keV) ~1e-11 cgs Fx (15-100keV) ~3e-13 cgs The case of Arp220: dust covered powerful SB? XMM observation: Low X-ray/FIR ratio even for a pure SB. Fe 6.7 keV line with high EW~2keV? (Iwasawa et al. 05)

  13. The case of Arp220 Flux 10-40 keV~8x10-13 cgs L(2-10 keV)~1042 erg/s 2000 MPD counts 700 CZT counts Assuming that the 2-10 keV emission is 3% of the intrinsic AGN emission obscured by NH ~5x1024cm-2 100 ksec SimbolX observation will be able to unveil the AGN even if it is not a dominant contributor to the IR emission.

  14. Summary and conclusion ULIRGs are generally faint X-ray sources and require sensitive high energy observations to be detected 15 local ULIRGs; few observation above 10keV among the 7 SB-ULIRGs. Observation not enough sensitive to detect faint sources like ULIRGs • NH~3-5x1024cm-2 • flux detected in the 2-10 keV band is 3% of a putative AGN With 100 ksec observations, we will collect 100-700 counts above 10 keV with the CZT. Measure the AGN intrinsic luminosity in ULIRGs and disentangle their contribution to the SB emission

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