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The nature of X-ray selected Broad Absorption Line Quasars

The nature of X-ray selected Broad Absorption Line Quasars. Alex Blustin. UCL-MSSL and IoA, Cambridge. With Tom Dwelly (Southampton), Mat Page (UCL-MSSL) ‏. X-ray Universe 2008, Granada, Spain. What are Broad Absorption Line Quasars (BALQSOs)?. Quasars with very broad

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The nature of X-ray selected Broad Absorption Line Quasars

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  1. The nature of X-ray selected Broad Absorption Line Quasars Alex Blustin UCL-MSSL and IoA, Cambridge With Tom Dwelly (Southampton), Mat Page (UCL-MSSL)‏ X-ray Universe 2008, Granada, Spain

  2. What are Broad Absorption Line Quasars (BALQSOs)? • Quasars with very broad • restframe UV absorption • features from the wind: • z ~ 0.1 – 6 • wind outflow speed up to • 60,000 km/s • NH ~ 1024 cm-2 Rarely detectable in X-rays due (probably) to high absorption from the ionised wind

  3. Why have we started to find BALQSOs in X-ray surveys? Optically-selected (OBALQSOs): discovered in optical surveys X-ray selected (XBALQSOs): discovered in X-ray surveys

  4. Why have we started to find BALQSOs in X-ray surveys? Optically-selected (OBALQSOs): discovered in optical surveys X-ray selected (XBALQSOs): discovered in X-ray surveys Are they easier to detect in the X-rays due to low absorption from the wind? Are they exceptionally luminous BALQSOs with high dust extinction (hence faint in optical but bright in X-rays)? Do they have intrinsically higher X-ray to optical flux ratios?

  5. XBALQSOs in two deep XMM-Newton X-ray survey fields WHT-AF2 WYFFOS z = 2.63 Keck-LRIS z = 1.793 1H field ~100 ks XMM EPIC Keck-LRIS z = 1.40 Keck-LRIS z = 2.64 CDFS ~400 ks XMM EPIC VLT-FORS Szokoly et al. 2004 z = 2.82

  6. XBALQSOs in two deep XMM-Newton X-ray survey fields WHT-AF2 WYFFOS z = 2.63 Keck-LRIS z = 1.793 1H field ~100 ks XMM EPIC Keck-LRIS z = 1.40 Keck-LRIS z = 2.64 CDFS ~400 ks XMM EPIC VLT-FORS Szokoly et al. 2004 z = 2.82 C IV 1549 Å absorption from wind

  7. Fitting the X-ray absorption due to the wind Few X-ray counts in spectra We need to make some assumptions: • Same velocity structure as in UV • Standard Spectral Energy Distribution (SED)/continuum for absorber model generation and spectral fitting • Same ionisation parameter x and column NH for all velocity components

  8. Velocity structure of the (rest-frame) UV-absorbing wind Vout = 670, 2170 km/s FWHM = 1140, 2610 km/s FWHM = 2430 km/s Vout = 1680 km/s Vout = 4100, 1330 km/s FWHM = 2390, 1460 km/s FWHM = 3790, 5210 km/s Vout = 12740, 18750 km/s Vout = 1900, 4220 km/s FWHM = 1940, 3220 km/s

  9. X-ray to optical slope set using aox calculated from 2500 Å flux (Vignali, Brandt & Schneider 2003)‏ Spectral Energy Distributions Based on Marconi et al. 2004 Read-out from refl reflection model in SPEX 2.00.11

  10. X-ray fits • Three free parameters: • continuum normalisation • absorbing column NH • ionisation parameter x Spectra from XMM-Newton EPIC (combined)‏

  11. Is there less X-ray absorption from the wind in XBALQSOs? PG1115+080 (Chartas et al. 2007)‏ Q1246-057 (Grupe et al. 2003)‏ SBS1542+541 (Grupe et al 2003)‏ PG2112+059 (Gallagher et al. 2004)‏ OBALQSOs

  12. Is there less X-ray absorption from the wind in XBALQSOs? If so, XBALQSOs here PG1115+080 (Chartas et al. 2007)‏ Q1246-057 (Grupe et al. 2003)‏ SBS1542+541 (Grupe et al 2003)‏ PG2112+059 (Gallagher et al. 2004)‏ OBALQSOs

  13. Is there less X-ray absorption from the wind in XBALQSOs? If so, XBALQSOs here OBALQSOs XBALQSOs

  14. Is there less X-ray absorption from the wind in XBALQSOs? Probably not OBALQSOs XBALQSOs Nearby AGN (Blustin et al. 2005)

  15. How does the UV absorption by the wind compare? Consistent with amount of UV line absorption in SDSS OBALQSOs SDSS OBALQSOs from Trump et al. 2006

  16. Are XBALQSOs just highly luminous BALQSOs with extra dust extinction? Expected B-Ks for SDSS QSOs Vanden Berk et al. 2001 No, consistent with OBALQSOs OBALQSOs (Gallagher et al. 2006)‏ XBALQSOs

  17. X-ray flux, optical flux and aox Log 2500 Å flux OBALQSOs: median aox = -2.20 (stdev 0.21)‏ XBALQSOs: median aox = -1.90 (stdev 0.13)‏ Given the median UV fluxes of the samples, the Vignali, Brandt & Schneider (2003) relation predicts a 0.13 difference in aox; we observe a difference of 0.30. Log 2 keV flux aox OBALQSOs (Gallagher et al. 2006)‏ XBALQSOs

  18. X-ray flux, optical flux and aox Log 2500 Å flux OBALQSOs: median aox = -2.20 (stdev 0.21)‏ XBALQSOs: median aox = -1.90 (stdev 0.13)‏ Given the median UV fluxes of the samples, the Vignali, Brandt & Schneider (2003) relation predicts a 0.13 difference in aox; we observe a difference of 0.30. Log 2 keV flux The XBALQSOs may have an intrinsically higher X-ray to optical flux ratio than the OBALQSOs aox OBALQSOs (Gallagher et al. 2006)‏ XBALQSOs

  19. Conclusion: These XBALQSOs are probably not fundamentally different from the broader BALQSO population. However - they are relatively X-ray rich. Deep (hard) X-ray surveys are now sensitive to this part of the AGN population... As (hard) X-ray surveys get deeper, we can expect to detect a lot more BALQSOs like these in X-rays.

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