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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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slide1

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

slide2

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

slide3

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

slide4

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?

slide5

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

slide6

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

slide7

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
slide8

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

slide9

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

slide10

X-ray fits

  • Three free parameters:
  • continuum normalisation
  • absorbing column NH
  • ionisation parameter x

Spectra from XMM-Newton

EPIC (combined)‏

slide11

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

slide12

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

slide14

Is there less X-ray absorption from the wind in XBALQSOs?

Probably not

OBALQSOs

XBALQSOs

Nearby AGN (Blustin et al. 2005)

slide15

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

slide16

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

slide17

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

slide18

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

slide19

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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