ULIRGs in hard Xray: From XMM to Simbol X

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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

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1.ULIRGs are predominantly powered by heavily
dust enshrouded AGN or circumnuclear SB?
ULIRGs are a class of sources with LIRgt1012L?
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?

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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?

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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 kT0.7 keV is always present
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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.
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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
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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
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The AGN in IRAS 19254-7245 XMM and L band
observations
Strong reflected continuum plus a scattered power
law, Fe line at E6.4 keV (EW1 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
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IRAS19254-7245 Suzaku I
Sey2 z0.287
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 Fe800eV)
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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

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Whats 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 gt1e25 LX ? Norm 35 6000 cts MPD
1400 CZT

• NH3 ?1
• LX10-20

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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 EW2keV?
(Iwasawa et al. 05)
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The case of Arp220
Flux 10-40 keV8x10-13 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.
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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

• NH3-5x1024cm-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