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): [OIII], HeII [FeIII], ArIV etc…

Ultraluminous X-ray Sources (ULXs) L X ≥ erg/s non-nuclear compact sources Eddington limit for ~ 10 M  (usual a for stellar-mass BH) Not AGNe! Not young SNRs! (can be ~10 40 erg/s bright) Unknown nature!

Most popular models: -IMBH with a massive donor star critical (Eddington) rate -Supercritical accretor like SS433 with a thick disk with a funnel, seen face-on

Observational Properties: -Luminosities erg/s in the standard X-ray range (Chandra 0.5-8keV) -Powerlaw or powerlaw+soft excess (T ~ keV) 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 )

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

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

IC 342 X-1 “Peculiar SNRs”

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

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

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

Observations with the 6m SAO telescope Spectrographwavelength range,Åspectralseeing, resolutionarcsec MPFS (panoramic) ~10001,5 SCORPIO (long-slit) ~20001,5 MPFS FOV Long Slit 1˝1˝

HαHα HβHβ [SII] ( ) [OIII] ( ) HeII4686 [NII] ( ) Emission lines’ mapping: 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 1˝1˝ 1˝1˝

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

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

 [OIII]5007 HH HeII 4686 H  [OIII] 4959 [OIII] 5007 Two-component lines: V 2 -V 1  km/s Broader component width ~ km/s

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

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

SHOCK WAVES OR PHOTOIONIZATION? MF16 from Evans et al., 1999  Photoionization by power law continuum (labelled by ionization parameter logarithm lgU) 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/n 1/2 =

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

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

Pure photoionization models (CLOUDY modeling results): Photoionization best-fit: lgT(K) = 5.15±0.05 (T~ K) F = 0.6 ± 0.1 erg/cm 2 /s fixed X-ray spectrum (best-fit from Roberts&Colbert, 2003), with dilution corresponding to 13pc + black body with temperatures (3-30) 10 4 K and integral flux densities erg/cm 2 /s => UV luminosity ~10 40 erg/s Central source emitting:

Other high-excitation nebulae:

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

High-excitation nebulae: HoII X-1

Bubble nebulae: HoIX X-1

Bubble nebulae: IC342 X-1

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

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

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

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

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

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

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