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Nebulae Associated with Ultraluminous X-ray Sources

Nebulae Associated with Ultraluminous X-ray Sources. P. Abolmasov , Special Astrophysical Observatory. Very commonly used ionization diagram. Collisionally excited (shocks or X-rays): [NII]6583,6448 [SII]6717,6731 [OI]6300,6364. “High excitation” (ionization potential > 1Ry):

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Nebulae Associated with Ultraluminous X-ray Sources

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  1. Nebulae Associated with Ultraluminous X-ray Sources P. Abolmasov, Special Astrophysical Observatory

  2. Very commonly used ionization diagram Collisionally excited (shocks or X-rays): [NII]6583,6448 [SII]6717,6731 [OI]6300,6364 “High excitation” (ionization potential > 1Ry): [OIII], HeII [FeIII], ArIV etc…

  3. Eddington limit for ~ 10 M (usual a for stellar-mass BH) Not young SNRs! (can be ~1040 erg/s bright) Not AGNe! Ultraluminous X-ray Sources (ULXs) LX≥ 1039 erg/s non-nuclear compact sources Unknown nature!

  4. Most popular models: • IMBH with a massive donor star accreting @ 0.01-1 critical (Eddington) rate • Supercritical accretor like SS433 with a thick disk with a funnel, seen face-on

  5. Observational Properties: • Luminosities 1039-1041 erg/s in the standard X-ray range (Chandra 0.5-8keV) • Powerlaw or powerlaw+soft excess(T ~ 0.1-0.2keV) X-ray spectra • ~1 per 20 giant spirals • Connected to the young stellar population (5-20 Myr…) • Some have radio counterparts (NGC5408 X-1, HoII X-1) • Some have point-like optical counterparts identified with OB supergiants • Some are close to massive star clusters (usually offset by tens of parsecs) • Many have nebular counterparts (ULX nebulae)

  6. ULX nebulae: • Shock excitation ([SII], [NII], [OI] etc. ) • Large sizes, ~50-500pc • HeII λ4686 emission (stellar?) What are they? MH9/10, the optical counterpart of HoIX X-1 (Grisé et al., 2006) • SNRs? (too powerful) • Superbubbles? (lack of young stars) • X-ray ionized nebulae? (requires too much X-rays in some cases!)

  7. HoII X-1 Ho IX X-1 NGC6946 ULX1 (=X8, X11)

  8. IC 342 X-1 “Peculiar SNRs”

  9. Our results from the 6m: Eight ULX nebulae Two spectrographs : -- MPFS (panoramic) -- SCORPIO (long slit) Medium spectral resolution (Δ ~ 5-10Å) Spectral range 4000-7200Å

  10. from Blair&Fesen, 1994 MF16 (counterpart of NGC6946 ULX-1): 34pc (~1,˝5) (HST ACS, filter F658N) X-ray source coordinates: 20h 35m 00s.75 +60˚ 11' 30".9 But: HeIIλ4686 / Hβ ~ 0.2 !! 20pc (~1˝) Radio isophotes (VLA) LX ≈ 2.5 1039 erg/s (0.5-8.0 keV) L(H) ≈ 2 1038 erg/s L(optical lines, total) ≈ 2 1039 erg/s Also a bright radio source

  11. MF16 NGC 6946 galaxy: D = 5,5 (from 5,1 to 5,9) Mpc Scd, active star formation

  12. Observations with the 6m SAO telescope 1˝ Spectrograph wavelength range,Å spectral seeing, resolution arcsec MPFS (panoramic) 4000-7000 ~1000 1,5 SCORPIO (long-slit) 4000-5700 ~2000 1,5 Long Slit MPFS FOV

  13. [OIII] (5007+4959) Hα Barycenter shift: line   H : -0,111 -0,088 ±0,013 H : -0,11 -0,10 ±0,02 HeII : 0,72 -0,02 ±0,02 [OIII] : 0,058 0,011 ±0,015 [SII] : -0,116 -0,081 ±0,014 [NII] : -0,061 -0,064 ±0,013 Hβ 1˝ [NII] (6548+6583) HeII4686 Emission lines’ mapping: 1˝ [SII] (6717+6731)

  14. SCOPRIO spectrum: Integral spectrum: Very rich high-excitation spectrum (HeII, FeIII, OIII) and bright shock-ionized lines (SII, NII, OI).  MPFS total spectrum

  15. Possible interpretations – fast (photoionizing) shock waves or photoionization by a broadband continuum…

  16. Two-component lines: HeII4686 H [OIII]4959 [OIII]5007 V2-V1 120-130 km/s [OIII]5007 Broader component width ~ 200-300km/s H

  17. VS • Total luminosity in H (if the shock surface area is given); • Shock velocity estimate from the component ratio: For a single H line: precursor Shock (cooling matter) (from Dopita&Sutherland, 1996)

  18. Single Hβ line kinematics nH, cm-3 L(Hβ) = (7,2±0,4) 1037 erg/s Narrow-to-broad components ratio 1,85±0,19 Additional source of excitation/ionization?

  19. MF16 MF16 Photoionization by power law continuum (labelled by ionization parameter logarithm lgU) from Evans et al., 1999  SHOCK WAVES OR PHOTOIONIZATION? Only lgU~-5 can be provided by the extrapolated model for X-ray spectrum (Chandra data, taken from Roberts&Colbert, 2003), lgU~-2.7 needed B/n1/2 =

  20. Using single recombination line Weakly varying function of physical conditions Total effective recombination coefficient for He++ for Case B Recombination with HeII4686 emission coefficient L<228Å ≥ 1039erg/s

  21. HeII4686 MF16 L(HeII)=1.6 1037 erg/s Cannot be explained by a shock wave, and an EUV source needed with L<228Å≥ 1039erg/s Or X-ray source with L ~ 1041 erg/s or larger! Photoionization by power law continuum (labelled by ionization parameter logarithm lgU)

  22. Pure photoionization models (CLOUDY 96.01 modeling results): Central source emitting: fixed X-ray spectrum (best-fit from Roberts&Colbert, 2003), with dilution corresponding to 13pc + black body with temperatures (3-30) 104K and integral flux densities 0.3-7.0 erg/cm2/s Photoionization best-fit: lgT(K) = 5.15±0.05 (T~120 000K) F = 0.6 ± 0.1 erg/cm2/s => UV luminosity ~1040erg/s

  23. Other high-excitation nebulae:

  24. M101 P098 from the work of Kuntz et al (2001)

  25. High-excitation nebulae: HoII X-1

  26. Bubble nebulae: HoIX X-1

  27. Bubble nebulae: IC342 X-1

  28. HeII4686 accompanied by other high-excitation lines, both allowed and forbidden (MF16)

  29. PNe Seyfert NLRs Photoionized HII regions ULXNe SNRs Both high-excitation and low-excitation lines are enhanced everywhere! Compare with Baldwin’s picture!

  30. Unification scheme for ULNXe? High EUV luminosity / small shell (the case of MF16): Low EUV luminosity / large shell size (the case of HoIX X-1 and IC342 X-1): Shock-ionized shell X-ray source Very large diffuse shell or no shell at all (M101 P098) Strömgren zone

  31. In the framework of supercritical accretor model: Supercritical wind photosphere emitting EUV quanta! Higher mass-loss rate: Wind photosphere Lower mass loss: Thin wind-blown bubble

  32. W50 (VLA) HST images B  H+[NII]

  33. [OIII]5007 / H ~ 8 ?!! Optical filaments Optical emission of W50: Zealey et al.,1980 50pc L(H) ~ 1039 erg/s ?!!

  34. Conclusions: • All the observed ULX nebulae are at least partially shock-powered • Practically all of them contain signatures of high excitation (bright HeII, [OIII] lines) • To explain the spectra of some of them, EUV source is needed even brighter than the X-ray source • Many of ULXs most likely have wind/jet activity similar to that of SS433

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