1 / 28

General introduction Slim disk model (simplified model) Observational tests - case of ULXs

Super-Critical Accretion Flow? Shin Mineshige (Kyoto Univ.) with K. Ohsuga, K. Vierdayanti, K. Ebisawa, T. Kawaguchi AGN conference @ Xian (10/16/2006). General introduction Slim disk model (simplified model) Observational tests - case of ULXs 2D radiation-hydrodynamical (RHD) simulations.

cana
Download Presentation

General introduction Slim disk model (simplified model) Observational tests - case of ULXs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Super-Critical Accretion Flow?Shin Mineshige(Kyoto Univ.)with K.Ohsuga, K.Vierdayanti, K.Ebisawa, T.KawaguchiAGN conference @ Xian (10/16/2006) • General introduction • Slim disk model (simplified model) • Observational tests - case of ULXs • 2D radiation-hydrodynamical (RHD) simulations

  2. 1. Introduction (background) It is widely believed that the luminosity (L) of any accreting objects cannot exceed the Eddington luminosity (LE). ・What is the Eddington luminosity? ・What do we know from observations?

  3. What is the Eddington luminosity? Spherical accretion system cannot shine at L>LE. accreting gas accreting gas radiation pressure Gravity>rad.pressure ⇒GM/r2 >κF/c ⇒L<LE=4πCGM/κ (∵F=L/4πr2)

  4. radiation pressure accreting gas accreting gas Diskaccretion may achieve L>LE Super-Eddington flux (F>LE/4πr2) is possible becauseofradiationanisotropy(!?)

  5. What is Photon trapping? Begelman (1978), Ohsuga et al. (2002) When photon diffusion time (Hτ/c) exceeds accretion time, photons are trapped within flow. . rtrap~ (Mc2/LE)rs Low-energy photons Low-energy photons BH radiative diffusion & accretion High-energy photons trapped photons (c) K. Ohsuga

  6. IC342 galaxy UltraLuminousX-raysources(ULXs)Makishima et al. (2000), van der Karel (2003) • Bright (~1040ergs-1) compact X-ray sources • Successively found in off-center regions of nearby galaxies. • If L<LE, black hole mass should be > 100 Msun. LE~1038(M/Msun) erg s-1 • Two possibilities • Sub-critical accretion onto intermediate-mass BHs (M>100Msun). • Super-critical accretion onto stellar-mass BHs (M~3-30Msun).

  7. Narrow-lineSeyfert1galaxies(NLS1s) Boller et al. (NewA 44, 2000) • What are NLS1s? • Narrow “broad lines” (< 2000kms-1) • Seyfert 1 type X-ray features • Extremesoft excess & variability • Seem to contain less massive BHs • Good analogy with stellar-mass BHs in their very high (largeL) state. • High Tbb(∝MBH-1/4) ⇒ large soft excess • Small (GMBH/RBLR)1/2⇒ narrow line width NLS1s = high L/LE system

  8. 2. Slim disk model Slim disk model was proposed for describing high luminosity flows as an extension of the standard disk. ・What is distinct from the standard disk model? ・What are its observational signatures?

  9. L=LE log L/LE . . logm≡logM/(LE/c2) Slim disk modelAbramowicz et al. (1988); Watarai et al. (2000) • Basics This occurs within trapping radius rtrap~(Mc2/LE)rs • Model Similar to the standard disk model; radially one-zone model but with radiation entropy advection accretion energy partly trapped photons .

  10. . M/(LE/c2)=1,10,102,103MBH=105Msun Slim-disk signatures1.smallinnermostradius 2.flatter temp. profile 3rS Slim-disk calculationsMineshige, Manmoto et al. (2002) Wang & Zhou (1999), Watarai & Fukue (1999) Low M rin～3rS ;Teff∝r-3/4 High M rin～rS;Teff∝r-1/2 . .

  11. Fν ν1/3 (smallr) hν ν-1 Fν (smallr) hν Spectral properties(e.g. Kato et al. 1998) Disk spectra = multi-color blackbody spectra Temperature profiles affect spectra T∝r-p ⇒ F∝ν3-(2/p) ・standard disk (p=3/4) ⇒F∝ν1/3 ・slim disk (p=1/2) ⇒F∝ν-1

  12. 3. Observational tests: Case of ULXs We examined the XMM/Newton data of several ULXs which were suggested to be candidates of intermediate-mass black holes. ・How to test the theory? ・What did we find?

  13. P-free disk model(Mineshige et al. 1994) Fitting with superposition of blackbody (Bν) spectra: Fitting parameters: Tin= temp.of innermost region (～max.temp.) rin = size of the region emitting with Bν(Tin) p= temperature profile ⇒ Good fits to the Galactic BHCs with p=0.75

  14. Spectralfitting1.Conventionalmodel(Roberts et al. 2005) Fitting with disk blackbody (p=0.75) + power-law We fit XMM-Newton data of several ULXs ⇒ lowTin～0.2keVandphoton index ofΓ=1.9 If we set rin~3rS, BH mass is MBH~300Msun. log conts NGC5204X-1 loghν

  15. Problem with DBB+PLfitting Spectral decomposition of DBB& PL components DBB comp. is entirely dominated byPL comp. Can we trust values derived from the minor component? log conts NGC5204X-1 loghν

  16. Spectralfitting2.p-freemodel(Vierdayanti et al. 2006, PASJ in press) P-free model fitting, assuming T∝r-p We fit the same ULX data but with p-free model only ⇒highTin~2.5keVandp=0.50±0.03(noPLcomp.) MBH~12Msun & L/LE~1, supporting slim disk model. log conts NGC5204X-1 loghν

  17. Why can both models give good fits? Because the spectral shapes are similar below ~10 keV. power-law (Γ=2) p-free with p=0.5 Both show fν∝ν-1 in 0.1~10keV range.

  18. The same test is needed for NLS1s Spectral fitting:Summary(Vierdayanti et al. 2006, PASJ in press; astro-ph/0609017) P-freemodelfitting gives MBH <30Msun. Low-temperature results should be re-examined!! logLx No evidence of IMBHs so far logkT (keV)

  19. 4. Radiation Hydrodynamical simulations The slim-disk model applies only to the flow with L ~ LE. For even higher L, we need radiation-hydrodynamical (RHD) simulations. ・What are the properties of the simulated flow? ・What can we understand them?

  20. 500 z/rs Injection 500 BH r/rs Our RHD simulationsOhsuga, Mori, Nakamoto, S.M. (2005, ApJ 628, 368) • First simulations of super-critical accretion flows in quasi-steady regimes. (cf. Eggum et al. 1987; Kley 1989; Okuda 2002; …) • Matter with0.45KeplerianA.M. is continuously added through the outer boundary → disk-outflow structure • Flux-limited diffusion adopted. • Mass input rate: 1000(LE/c2) →luminosity of~3LE Initiallyemptydisk

  21. Overview of 2D super-critical flow Ohsuga et al. (2005, ApJ 628,368) Case of M=10Msun & M=1000LE/c2 ・ outflow z/rs disk flow BH r/rs density contours & velocity fields gas energy radiation energy density density (c) K. Ohsuga

  22. Radiation energy density is high;Erad ≫EEdd≡LE/4πr2c. Then why does the radiation not prevent accretion? Note radiation energy flux is Frad∝(κρ)-1∇Erad. → Highρand flatEradprofile result in weak Prad force. Lowρand strong Prad yield super-Eddington flux. Why is accretion possible? Ohsuga & S.M. (2006, submitted)

  23. Gas & radiation flow:summary Ohsuga & S.M. (2006, submitted) In the disk region: large gas density flat Erad profile (+ photon trapping) → weak Prad force → slow accretion In the outflow region: low gas & rad.density → strong Prad force → high-vel. outflow

  24. BH Density contours Significantradiationanisotropy Ohsuga et al. (2005, ApJ 628,368) luminosity 12 our simulations 4D2F()/LE 8 4 0 viewing angle The observed luminosity is sensitive to the viewing-angle; Maximum L ~ 12 LE!! ⇒ mild beaming (c) K. Ohsuga

  25. gas gas What are the causes of beaming? Heinzeller, S.M. & Ohsuga (2006, MNRAS, astro-ph/0608263) Photon energy increases as θdecreases, why? - Because we see photons from deeper, hot region. - Because of (relativistic) Doppler effect. Photon number increases as θdecreases, why? - Because of anisotropic gas distribution. - Because Iν/ν3 is Lorentz invariant & hνincreases. radiation

  26. Further issues (1) Line spectra of super-critical flow X-ray absorption in quasars?(Pounds et al. 2003) • Outflow of 0.05-0.2c in X-ray spec. • Mass outflow rate~the Eddington rate • Can be explained by Prad driven wind. Same for BAL quasars?

  27. Further issues (2) Interaction with magnetic fields Magnetic fields are essential ingredients in disks • Photon-bubble instability (Begelman 2002) • Magnetic tower jet → global RHD+MHD simulations necessary (Kato, S.M., & Shibata 2004)

  28. Conclusions • Near- and super-critical accretion flows seem to occur in many systems (ULXs, NLS1s…?). • Slim disk model predicts flatter temperature profile. Spectral fitting with p-free model proves the presence of supercritical accretion in ULXs. How about NLS1s? • 2DRHDsimulationsofsuper-criticalflowshowsuper- Eddingtonluminosity,significant radiation anisotropy (beaming), photon trapping, high-speed outflow, etc. L can be ~10 LE!! • Issues:line spectra,magneticfields, jet formation,…

More Related