1. Accretion Physics in the SDSS/XMM-Newton Quasar Survey Monica Young with Martin Elvis, Alan Marscher & Guido Risaliti

2. SDSS/XMM Quasar Survey Optical: SDSS DR5 quasars –90,611 quasars –0.1 < z < 5.4 X-ray: XMM-Newton –Large field of view 1% overlap between archive and SDSS –Large effective area  light bucket Result: 792 quasars with X-ray observations –Available on HEASARC archive

3. 3 Optical/X-ray Trends 1. α ox -L opt 2. Γ vs. L x 3. Γ vs. L/L edd X-ray loud Steffen et al. 2006 X-ray quiet Shemmer et al. 2008 Green et al. 2009

4. 3 Optical/X-ray Trends 1. α ox -L opt 2. Γ vs. L x 3. Γ vs. L/L edd X-ray loud Young et al. 2009 X-ray quiet Risaliti, Young & Elvis 2009 Young et al. 2009

5. Monte Carlo Population Study Define sample: 10 6 quasars –Draw (z,L opt ) randomly from quasar luminosity function (Hopkins et al. 2007) Apply SDSS and XMM-Newton selection –SDSS selection/flux limits –XMM 6 σ sensitivity: fn(T exp, θ ) Find out which relations are intrinsic to the parent population

6. Optical/X-ray Trends 1. The α ox -L opt Relation

7. α ox = normally distributed around = -1.6, σ = 0.17 α ox = -0.137*log L 2500 + 2.64, σ = 0.15 ( Steffen+06)  Selection effects cannot reproduce correlation! Is α ox -L opt Real?

8. α ox -L opt stronger effect in X-ray energy 1500 Å 5000 Å 1 keV 4 keV Slope and scatter change strongly with X-ray energy log L 1500 log L 5000 α ox

9. Slope of α ox -L opt Relation Slope steepest at low X-ray energy Closer to linear at highest energies Change in correlation slope is not due to change in baseline over which α ox is defined Slope of α ox -L opt X-ray Energy (keV) “Baseline Effect” To understand why, need to understand the Γ -L x anti-corr. 1keV 10keV

10. Optical/X-ray Trends 2. The Γ -L x Relation

11. The Γ -L x Relation Significant correlation above 2 keV –Consistent with Green et al. 2009 –Strengthens with X-ray energy 2 keV10 keV Green+09 Young+09 3.0 σ significance 8.6 σ significance

12. Simulated Γ -L x Relation: Assume Γ = f(L bol /L Edd ) log L 2 keV Γ 0.7 σ significance 6.0 σ significance log L 10 keV Γ Correlation strengthens artificially with energy But artificial correlation not significant at L 2 Observed slope Simulated slope

13. Simulated Γ -L x Relation: Assume Γ = f(L x, L bol /L Edd ) If X-ray slope is a function of L x and L bol /L Edd, then observed slope, strength reproduced 4.3 σ significance 9.0 σ significance Observed slope Simulated slope

14. Γ -L x Correlation Due to Soft Excess? L x -z correlated (flux-limited) –Soft excess enters X-ray spectrum at low z Make redshift cut: z > 1  Γ -L x correlation disappears Is soft excess strength related to z or to L x ? – Subject of future study

15. Γ -L x Relation Steepens α ox -L opt Simulation shows that α ox -L opt slope changes with energy due to Γ -L x anti-correlation Γ = f(L bol /L edd ) Γ = f(L 2 keV ) Observed Simulated X-ray Energy (keV) Slope of α ox -L opt

16. α ox -L opt Independent of Baseline Account for effect of Γ -L x relation on α ox -L opt slope  α ox -L opt slope is independent of optical and X-ray reference frequencies  Implies constant α opt, Γ with respect to luminosity log ν (Hz) log ν F ν (ergs cm -2 s -1 ) Schematic Diagram X-rays (corona) Opt/UV (disk)

17. What drives α ox ? L opt is the primary driver of α ox BUT accretion rate is a secondary driver –Partial correlation ( α ox, L/L Edd, L opt )  7 σ X-ray faint X-ray bright log L/L Edd  Seed photon luminosity and accretion rate both drive X-ray efficiency

18. α ox and Comptonization Models Heating rate ~ l h ~ L x /R x Cooling rate ~ l s ~ L o /R o α ox  l h / l s  geometry l h / l s >> 2 “photon-starved” l h / l s ~2 lhlh lh/lslh/ls Coppi 1999 Γ =1.6 T=2e9 K Thermal Comptonization Model

19. Physical Scenario (“Patchy” corona) As luminosity increases, so does the covering factor (i.e., more blobs). The corona cools as it intercepts more disk photons. The optical depth remains constant ( τ ~0.1), so Γ steepens: ΔΓ ~0.2 for Δ L 2 ~1.3 dex. (comparable to error in Γ ) Low L bol High L bol

20. Conclusions SDSS/XMM-Newton Quasar Survey (SXQS) is a powerful tool! –473 quasars with both optical and X-ray spectra – unprecedented sample size! –Monte Carlo population study quantifies selection effects in the survey Determine which relations are intrinsic –Γ -L x – not intrinsic (due to soft excess component at low z) –α ox -L opt – intrinsic –α ox -L opt slope constant with respect to the reference frequencies Implies α opt and Γ constant with respect to luminosity Disk-corona structure changes with L/L Edd –Use α ox -L opt as input to Comptonization models –To reproduce α ox -L opt relation, the heating to cooling ratio must decrease  covering factor of corona increases with luminosity (i.e., with L/L Edd ?) Next step: Defend thesis! (July 15)