Comptonization in Super-Eddington Accretion flow & growth timescale of SMBHs

1. Comptonization in Super-Eddington Accretion flow & growth timescale of SMBHs 2003ApJ...593...69K astroph/0304373 Kawaguchi, T. Observatoire de Paris, France Depart. of Astronomy, Kyoto Unviersity, Japan 2003. 10. 16

2. Abstract • Introduction • Numerical procedures • Numerical results • Observational tests of the model • Growth time scale of BHs • Discussion • Summary

3. Abstract 1:Super-Eddington accretion (slim disk) may occure on: ULXs, microquasars & NLS1s 2: Effects of electron scattering (opacity & comptonization) & relativistic correction on emergent spectra from super-Eddington disks are examined for stellar BHs and SMBHs 3: broadband spectra of PG 1448+273(NLS1) is reproduced by slim disk with \dot{m}=100, =0.01 4: Many transient & variable NLS1s: 3<\dot{m}<300, which implies that they are young: MBH/\dot{M}  106 years

4. 1. Introduction 1:Super-Eddington accretion’s is important for formation & evolution of SMBHs; May common in the young universe; the sources of UV-EUV photons; a laboratory to exame what we know on accretion 2:Some ULXs & Galctic microquasars show Lbol>Ledd, Tin1keV (indications of super-Eddington accretion rates. Other explanations: BHs’ spinning, intermediate BH mass, beamed radiation) 3:NLS1s are also candidates for super-Eddington accretion flow Narrow H, soft-x excess, rapid & large variability

5. 4:why this paper? Some papers, e.g. Szuszkiewicz et al.(1996), Wang et al.(1999) considered electron scattering’s effects, but didn’t address comptonization Big problem remains in the comparison of observed optical/UV-soft X-ray sepctra with slim disk model is: the predicted soft X-ray is too steep So, this paper…

6. 2. Numerical procedures 2.1: The structure of slim disk slim disk model: 4 conservation eqn.+state eqn. Conservation of mass, momentum, angular-momentum, energy Numerical methods: shooting/relaxation Note: diffusion approximation for radiation cooling is only valid for optically-thick regions and LTE

7. However, for high L>Ledd, large viscosity >0.01 (especially > 0.1), effective optically-thin zone (eff 1 or eff <1 ) appears in inner disk region. This leads to “overheating” and “temperature invertion” problems. (cf. Belovorodov 1998; Czerny & Elvis 1987; Ross et al. 1992; Shimura & Takahara 1993, 2003;) To aviod this, papers about slim disk are confined in low viscosity. Thus, a bridged formula that describes continuously the transion between optically thick and opticall thin regions is required. (cf. marmol90, liang91, wandel91, lasota91, kusunose92, luoliang94, artemova96, honma96, luoliang98, dullemond98, gulu00, panlu02, linlu03)

8. In the end of this subsection: the author referred to gas evaporation model (Meyer & Meyer-Hofmeister 1994). Evaporation becomes weak in super-Eddington accretion rate (Liu et al. 2002). The corona above the disk (my second paper)

9. 2.2: spectral calculations follow Czerny & Elvis 1987 to deal with the effects of opacity of electron scattering (i.e. modified BB) and of the energy exchange via compton scattering (i.e. comptonization). More precise treatment requres solving radiative transfer

10. comptonization effect: τeff=1 the last thermalization surface τes strong temperature dependency

11. 3. Numerical results 3.1: physcial quantities \dot{m} \rho Fig. 1 Opacities (Note effective optically-thin region)

12. \dot{m} \rho T  Fig. 2 Effective y*: comptonization is larger in super-Eddington accretion flow than sub-Eddington one

13. Fig. 3 Azimuthal velocity & radial velocity. Note: sub-Keplerian rotation location of transonic point

14. Fig. 4 Accretion timescale (solid lines) & diffusion timescale (dotted lines)

15. In the inner region of high \dot{m}, tacc<tdiff. Photons are difficult to radiate out, but are advected with the flow. This is photon trapping effect

16. Fig. 5 \dot{m} dependency of some physical quantities • H<=R • \rho  • temperature invertion: • Tcolor>T

17. Fig. 6 \alpha dependency \alpha , then \rho , T  we can have:

18. 3.2: emergent spectra SSD local BB on SLIM relativistic corrected electron scattering comptonization Fig. 7 each effect on the emergent spectra

19. Fig. 8 contributions from different radii to total spectra dotted lines: without electron scattering

20. Fig. 9  dependency of spectra Fig. 10 spectra of ULXs/microquasars strong comptonization

21. 4. Observational tests of slim disk • 4.1 The ideal object for the test • high \dot{m}(high luminosity) to see the difference with SSD, to avoid optically-thin region • low BH mass: hot enough for X-ray emission • How to estimate BH mass? three choices+other... • reverberation mapping: time consuming, only several objects’ mass can be got (Kaspi 2000) • FWHM of H  • FWHM of [O III] and use mass-velocity dispersion relation • mass-bulge relation: Magorrian relation

22. Fig. 11 How to chose the ideal object for model test He chosed PG 1448+273 & applied XMM-Newton time

23. 4.2 comparison of the models with PG 1448+273 data

24. Fig. 12 problem too boosted 1st example?

26. 4.3 predicted X-ray features: to be judged by future observation • only slim disk fits soft-X excess well. Is the spectrum distorted due to electron scattering? • Intrinsic spectral features? higher accretion rate with weaker corona, it’s possible to observe the intrinsic spectral features(bound-free, bound-bound processes) in soft-X band. But strong comptonization may smear these features. • Does the color temperature change with flux? Tin change with \dot{m} may indicate super-Eddington accretion in NLS1s. Wrong!!!] • Is photon trapping important or does convection dominated?

27. 5. Growth timescale of BHs The elapsed time of accretion is: MBH/dot{M}=0.5\dot{m}^{-1} G years Since we found \dot{m}=1000, some NLS1 including PG 1448+273is really young: its age is about 106 years. Such a high accretion rate will last only for short phase.

28. 6. Discussion 1. Highly variable AGNs: some NLS1 show giant amplitude x-ray variability. this may be due to high accretion rate. However, from fig. 13, the accretion rates are located in (3,300), so the variability is linked with thermal instability of middle branch on S-shaped curve. 2. Photon trapping may be reduced due to magnetized accretion rate. 3. ... 4. ...

29. Fig. 13 distribution of highly variable/transient AGNs

30. 7. Summary • we examined the effects of electron scattering (opacity and comptonization) & relativistic correction on the emergent spectra from slim disk • Effective optical depth < 1 for \dot{m} in (100,100). An improvement in the knowledge of the cooling rate will be requred in those parameter sets • 3. The spectra model has been applied to broadband spectra of NLS1s, e.g. PG 1448+273 • 4. Extremely high \dot{m} implies they are young • 5. moderately high accretion rate of highly variable NLS1 indicate it’s relevant to thermal instability