An XMMNewton study of HyperLuminous Infrared GalaxiesA. Ruiz, F.J. Carrera, F. Panessa IFCA (CSICUC)
HyperLuminous Infrared Galaxies (HLIRGs) are the most luminous objects in the Universe. They exhibit extremely high star formation rates, and most of them seem also to harbour an AGN. Xray studies of HLIRGs have the potential to unravel the AGN contribution to the bolometric output from these bright objects. We have selected a sample of HLIRGs with public observations in the XMMNewton archive. This is the first time that a systematic study of this type of objects is carried out in this spectral band. Their Xray spectra are characterized by the presence of a powerlaw continuum, associated to the AGN, and, in a few cases, a thermal component probably associated to the starburst (SB). We have looked up for relationship between the Xray and farIR (81000 m) luminosities. We find most HLIRGs are “mixed” sources: their Xray luminosities are too high to be produced by a SB, and their IR luminosities are too high to be produced by an AGN. Only two objects show Xray thermal emission. This could be explained, in some cases, by Compton thick obscuration. The Xray to IR luminosity ratio is constant with redshift, indicating that their respective power sources could be physically related.
IRAS 001827112
IRAS 09104+4109
IRAS 12514+1027
IRAS F14218+3845
IRAS F15307+3252
PG1206+459
Source Type z Γ S(0.510 keV)
IRAS 18216+6418 Sy1 0.297 1.43±0.08 0.44±0.06 10.7 45.5 45.1 46.76IRAS 001827112 Sy2 0.327 13 42.0 46.58IRAS 09104+4109 Sy2 0.442 1.66±0.07 11.7 44.5 46.84IRAS 12514+1027 Sy2 0.3 13.7 43.7 42.1 46.36IRAS F14218+3845 QSO 1.210 13 44.6 47.92IRAS F15307+3252 Sy2 0.926 13.6 43.7 47.31PG 1206+459 QSO 1.158 12.6 45.1 47.85
Stb 0.575 2 44.3 42.4 47.12
kT / keV EW / keV log(Lpo) log(Lth) log(LIR)
2.0+1.12.3 2.3+3.1
0.8
0.7+0.20.3
1.8+0.84.7 0.34+0.21
0.08
2.24±0.122.1±0.41.7±0.9
IRAS F00235+1024 (1)
Xray luminosity (210 keV) of the powerlaw component versus the IR luminosity (81000m) computed using IRAS fluxes (Perault 1987). The top grey area (“AGN zone”) indicates the IR luminosity expected (at 90% of confidence) for an AGN with the corresponding Xray luminosity (Elvis et al. 1994). The bottom grey area (“Starburst zone”) indicates the Xray luminosity expected for a starburst with the corresponding IR luminosity (Persic et al. 2004, Kennicutt 1998).✔ We find no clear correlation for HLIRGs, but they seem to follow the same
tendency as AGNdominated ULIRGs.
✔ Most of HLIRGs and all AGNdominated ULIRGs are “mixed” sources: their Xray luminosities are too high for a SB, and their IR luminosities are too high for an AGN.
✔ IRAS 18216+6418 is the only source that clearly shows AGNdominated properties. Compton thick obscuration could move up some HLIRGs from “mixed zone” to “AGN zone”.
Top: SFR corresponding to HLIRG IR luminosity (Kennicutt 1998), after the subtraction of the AGN contribution (Elvis et al. 1994) to the emission, versus redshift. The dotted line represents the SFR limit for HLIRGs (L
IR >1013L
⊙). The solid line is the SFR for a source with
IRAS fluxes equals to the completeness limits of the IRAS catalogue (0.5 Jy in 12, 25 and 60 m, 1.5 Jy in 100m). Bottom: ratio of 210 keV XR luminosity to IR luminosity versus redshift.
● HLIRGs (LIR
>1013L⊙) are strong candidates for being primeval galaxies (RowanRobinson 2000), in the process of a major episode of star formation. As they represent the
most vigorous stage of galaxy formation, they are a unique laboratorie to investigate extremely high star formation and its conection to supermassive black hole growth.● Objectives:
● Determining which is the relative contribution of SFR and AGN emission to the bolometric luminosity and their interplay.● Does the SB and AGN contributions change with cosmic time? What can we learn from HLIRGs about galaxy formation?● Which is their relation with the IR lower luminosity version, Ultra Luminous Infrared Galaxies (ULIRGs)?
● Sample: HLIRGs with redshift between 0.3 and 1.5 with public data in XMMNewton archive. We use the ULIRGs sample from Franceschini et al. 2003 to compare results.
Xray luminosity (0.510 keV) of the thermal component versus Xray luminosity (210 keV) of the powerlaw component. Dotted line is a correlation obtained by Franceschini et al. (2004) for starburstdominated ULIRGs.
✔ Only two HLIRGs present intrinsic thermal emission, while in all ULIRGs a thermal component have been observed: may Compton thick obscuration be the cause of the absence of Xray thermal emission in some objects?
✔ At odds, IRAS 18216+6418, whose emission is clearly AGNdominated, follow the same correlation as starburstdominated ULIRGs (Franceschini et al. 2004).
XMMNewtonXMMNewtonHLIRGs spectraHLIRGs spectra
Xray PL vs Far Infrared: Starburst or AGN?Xray PL vs Far Infrared: Starburst or AGN?
Redshift evolution?Redshift evolution?
Xray thermal vs PL: Where's thermal emission?Xray thermal vs PL: Where's thermal emission?
HLIRGs data and XMMNewton spectral analysisHLIRGs data and XMMNewton spectral analysis
●(1) Xray luminosities are upper limits from Wilman et al. 2003. [All fluxes are in erg s1 cm2 and luminosities in erg s1]
O HLIRG Obscured HLIRG✕ AGNdominated ULIRG✩ SBdominated ULIRG
Starburst
✔ An increment of SFR with redshift is observed, however this could be du to a selection effect.
✔ The ratio of hard XR to IR luminosity remains constant with z, suggesting that AGN and SB are physically conected at least below z~1.5.
✔ We need a sample at higher z to check this issue.
IRAS 18216+6418