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GALEX measurements of the Big Blue Bump as a tool to study bolometric corrections

GALEX measurements of the Big Blue Bump as a tool to study bolometric corrections. Elena Marchese R. Della Ceca, A. Caccianiga, P. Severgnini, A. Corral. Active Galactic Nuclei 9 – Ferrara , 24-27 May 2010. Accretion rate density. Total accreted mass.

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GALEX measurements of the Big Blue Bump as a tool to study bolometric corrections

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  1. GALEX measurementsof the Big BlueBumpas a tooltostudybolometriccorrections Elena Marchese R. Della Ceca, A. Caccianiga, P. Severgnini, A. Corral Active Galactic Nuclei 9 – Ferrara , 24-27 May 2010

  2. Accretion rate density Total accreted mass Active Galactic Nuclei, powered by accretion onto a Super-massive Black Hole (SMBH), emit over the entire electromagnetic spectrum with the peak of the accretion disk emission in the far-UV, a wavelength range historically difficult to investigate. • Study the spectral energy distribution (SED) of type 1 AGN in the optical, Near and Far-UV and X-ray energy bands . • Constrain the luminosity of the accretion disk emission component • Derive the hard X-ray bolometric correction factors for a significant sample of Type 1 AGN spanning a large range in z and Lx.

  3. The XMM-Newton Bright Survey in pills XMM fields used: 237 Covered Area (deg2): 28 Sources in the bright sample(BSS,0.5-4.5keV): 389 “ “ “hard” bright sample(HBSS,4.5-7-5 keV): 67 (56sources are in common) Total Sources: 400(fx>~7x10-14 erg cm-2 s-1) Della Ceca et al., 2004 Caccianiga et al., 2008 The starting point of our study is a sample of 304 AGNs, counting 263 type 1 AGNs having intrinsic NH <4 ·1021 cm-2, belonging to the XMM-Newton Bright Serendipitous Survey (XBS).

  4. The GALEX mission in pills GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer mission that is performing surveys of different depths/sky coverage in the far-UV and near-UV

  5. The sample 263 X-ray selected AGN 1, with NH <4 ·1021 cm-2 CROSS CORRELATION WITH GALEX 40 sources out GALEX field 63 upper limits 160 matches • All these sources have an X-ray spectra from XMM-Newton which allows us to derive X-ray luminosities and spectral properties (e.g. Γ, Nh). • Corral, Della Ceca, Caccianiga and Severgnini, 2010, in preparation • A. Corral:this meeting CROSS CORRELATION WITH SDSS 82 sources having data from XBS-GALEX-SDSS

  6. The model • The data points from the SDSS and from GALEX were described using a basic accretion disk model (DISKPN model in the XSPEC package). The maximum disc temperature was chosen in the range kT≈1-64 eV , and the normalization has been left has free parameter.

  7. Correctionstomeasuredfluxes Host Galaxy Our Galaxy AGN Hydrogenclouds (Lymanαforest) Intrinsic AGN reddening The exact shape of the extinction curve in the Near-Far-UV is still a matter of debate Observer Galacticreddening: Allen law(1976) Rv =3.1 EB-V = AB – AV available from the GALEX database Gaskell e Benker, 2007 determined a parametrized average extinction law from the study of 14 AGN, with FUSE and HST data. Bohlin et al. 1978

  8. Corrections to measured fluxes- IVOptical emission from the host galaxy SED OF ONE OF THE SOURCES About 20% of the sourceshaveopticalSEDsshowing a hardening at the opticalwavelengths. Opticalspectraofthesesourcescontaminationby the stars in the hostgalaxy SDSS GALEX AGN + hostgalaxy FLUX Calcium break ENERGY (kev) Break at 4000 Å : indicatorofthe importanceof the galaxy star-light in the total emissionof the source. Hostgalaxy AGN F+ e F-meanfluxdensities in the regions4050-4250 Å and 3750-3950Å (in the source rest-frame) respectively. Calcium- break

  9. Corrections to measured fluxes- IVOptical emission from the host galaxy Modelformulatedtocorrectfor the emissionof the hostgalaxy • Modelof a normalgalaxy: HeavisidefunctionsuchthatΔ=50% Ca break≈40% • Wecalculated the resultingΔfrom the combined emission of the AGN (with different normalizations) and host galaxy H.GALAXY+AGN • AGN: αν =-0.44 (αλ =-1.56). • (Vanden Berk et al. 2001) HOST GALAXY FLUX AGN λ (Å) H. GALAXY+AGN FLUX RATIO AGN/GALAXY FLUX AGN HOST GALAXY Break at 4000 Å λ (Å) Ca break≈2%

  10. BEFORE CORRECTION AFTER CORRECTION Δ=17.3% GAL+AGN AGN SDSS GALEX FLUX SDSS GALEX HOST GALAXY 0. 0. FLUX ENERGY(keV) ENERGIA (keV) ENERGY (keV) Δ=33.2% SDSS GAL+AGN FLUX SDSS FLUX GALEX GALEX 0. HOST GALAXY AGN ENERGY (keV) ENERGY (keV)

  11. Corrections to measured fluxesEmission lines contribution The presenceofemissionlineswithin the filterbandpass can contributesignificantlyto the observedmagnitudesofan AGN. Sincethiseffectis a strong functionofredshift, weneedto take itinto account to derive the continuum… TIPICAL SPECTRA OF AN AGN Assuming R ~1 FLUX WAVELENGTH (Å) Averagespectra and equivalentwidthsof the emissionlinespresent in the energybandswe are studying, calculatedbyTelferet al. 2002, from the spectraof 184 quasarswith z>0.33 .

  12. SPECTRAL ENERGY DISTRIBUTIONS OPTICAL-UV FLUSSI OTTICO-UV FLUSSI OTTICO-UV FLUSSI OTTICO-UV OPTICAL-UV X-ray (XMM) X-ray XMM FLUSSI X FLUSSI X FLUSSI X ENERGIA (keV) ENERGIA (keV) ENERGIA (keV) ENERGIA (keV) ENERGIA (keV) Medianmaximum temperature : kT ≈ 4 eV

  13. Availableforeveryobjectfrom the X-rayspectralanalysis (Corralet al. 2010) 2-10 keVluminosity Extrapolatedfrom the 2-10 keVluminosity, using the spectalindexmeasuredforeverysorce 0.1-100 keVluminosity Accretion disk luminosity Calculatedas the integralof the SEDs in the optical-UVbands. L bol=Ldisc + L 0.1-100 keV

  14. UV fluxes or their upper limits were fitted with the same model with a Tmax fixed to kT ≈ 4 eV 63 sources with XBS-GALEX upper limits 78 sources with XBS-GALEX data 82 sources with XBS-GALEX-SDSS data discussed so far

  15. Results - I CORRELATION LDISK – L2-10keV Strong dependenceof the accretion disk luminositiesto the X-rayluminosities the twoemissionmechanisms are highlycorrelated 78 sources XBS-GALEX 82 sources XBS-GALEX-SDSS Best-fit bisector relation: In good agreement withpreviousresults on X-rayselectedsources: Lusso et al. 2010: β=1.31±0.038 63 sources XBS-GALEX upper limits

  16. Results - II BOLOMETRIC CORRECTION AGAINST HARD X-RAY LUMINOSITY 63 sources XBS-GALEX upper limits 78 sources XBS-GALEX • We don’t find any significant correlation between bolometrc correction and X-ray luminosities • This is probably due to a very large spread in the distributions of the hard X-ray bolometric corrections, going from ~5 up to few hundred, implying a large dispersion in the mean SED 82 sources XBS-GALEX-SDSS

  17. Conclusions We used a sample of 223 sources spanning a large range in X-ray luminosities(LX ≈1041 – 1046 erg/s) and redshift (z≈0-2.4) and we find : • A high correlation between the accretion disk luminosity and the X-ray luminosity, in agreement with previous works on X-ray selected AGNs. • A very large spread in the distributions of the hard X-ray bolometric corrections, going from ~5 up to few hundred -> a large intrinsic dispersion in the mean SED; Thank you

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