The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev...

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The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX nebula MF16)

Transcript of The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev...

Page 1: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

The Optical Counterpart of NGC6946 ULX-1

P. Abolmasov,

S. Fabrika, O. Sholukhova, V. Afanasiev

Special Astrophysical Observatory, Russia

(a peculiar ULX nebula MF16)

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ULX nebulae:

MH9/10, the optical counterpart of HoIX X-1

(Grise 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?

Page 3: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

34pc (~1,˝5)

20p

c (~

1˝)

LLX X ≈≈ 2.5 10 2.5 103939 erg/s erg/s (0.5-8.0 keV)(0.5-8.0 keV)

L(HL(H) ) ≈≈ 2 10 2 103838 erg/s erg/s

L(optical lines, total) L(optical lines, total) ≈≈ 2 10 2 103939 erg/s erg/s

Also a bright radio sourceAlso 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.75 +60˚ 11' 30".9

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Observations with the 6m SAO telescopeSpectrograph wavelength range,Å spectral seeing,

resolution arcsec

MPFS (panoramic) 4000-7000 ~1000 1,5

SCORPIO (long-slit) 4000-5700 ~2000 1,5

MPFS FOV

Long Slit

Page 5: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

[OIII]5007

H

HeII4686H

[OIII]4959[OIII]5007

Two-component lines:

V2-V1 120-130 km/s

Broader component width ~ 200-300km/s

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(from Dopita&Sutherland, 1996)

,

,

7.69

866 H precursorS

H shock

FkmV s F

Total luminosity in H (if the shock surface area is given);

Shock velocity estimate from the component ratio:

For a single H line

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L(Hβ) = (7,2±0,4) 1037 erg/s

Narrow-to-broad components ratio 1,85±0,19kinematics

Additional source of excitation/ionization?

Single Hβ line

nH, cm-3

Page 8: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

SHOCK WAVES OR PHOTOIONIZATION?

MF16

MF16

from Evans et al., 1999

Photoionization by power law continuum (labelled by ionization parameter logarithm lgU)

13.6

1

eV

FU d

cn h

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 =

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L(HeII)=1.6 1037 erg/sHeII4686

Cannot be explained by a shock wave, and an EUV source needed with

L<228Å ≥ 1039erg/s

MF16

Photoionization by power law continuum (labelled by ionization parameter logarithm lgU)

Or X-ray source with L ~ 1041 erg/s or larger!

Page 10: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

… and other high-excitation lines

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Pure photoionization models (CLOUDY 96.01 modeling results):

Photoionization best-fit:

lgT(K) = 5.15±0.05

(T~120 000K)

F = 0.6 ± 0.1 erg/cm2/s

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

=> UV luminosity ~1040erg/s

Central source emitting:

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Conclusions:

●MF16 remains an enigma, but it is clearly much more than a SNR

●We estimate the expansion velocity for the nebula as 50-100 km/s, that is close

to the late-Sedov SNR expansion rate in a moderately-dense ISM (nH~1 cm-3)

●Shock waves seem to be short in explaining the observed optical emission-line

spectrum

●We suggest a photoionizaing source in H-ionizing UV (~1040erg/s) and He+-

ionizing EUV (>1039erg/s), needed to explain the high-excitation emission line

luminosities

Page 13: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

Thank you for attention!

Page 14: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

References:● Holt, S. S., Schlegel E. M., Hwang, U., & Petre, R. 2003, ApJ, 588, 792● Dunne, C. D., Gruendl, R. A., & Chu, Y.-H. 2001, AJ, 119, 1172● Liu, Z.-F. & Bregman, J. N., 2005, ApJSS, 157, 59● Roberts, T. P. & Colbert, E. J. M., 2003, MNRAS, 341, L49● Blair, W. P., Fesen, R. A., Schlegel, E. M., 2001, AJ, 121, 1497● Schlegel, E. M., Blair, W. P., Fesen, R. A., 2000, AJ, 120, 791● Blair, W. P., Fesen, R. A., 1994, ApJ, 424, L103● Lira, P., Lawrence, R. A., Johnson, A., 2000, MNRAS, 319, 17● Pakull, M. W., Mirioni, L., 2003 RevMexAA, 15, 197● Van Dyk, S. D., 1994, ApJ, 425, L77● Lehmann, I. et al., 2005, A&A, 431, 847

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MF16 – main properties:

X-rays not from the SNR! –Roberts & Colbert, 2003

Bright (L ~ 2 1039 erg/s in optical emission lines only) emission line region 1×1.5arcsec (2034 pc) with a SNR-like spectrum [SII] 6717,6731 / H ~ 1; bright [NII] 6548,6583, [OI] 6300, 6364

from Blair&Fesen, 1994

●total x-ray luminosity > 1039 erg/s (>> Cas A)●“ULX-like” X-ray spectrum, i e, soft MCD+PL●short-timescale variability (minutes)●point source (with Chandra resolution, d < 0.7 arcsec)

in X-rays

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HST images

B

H+[NII]

W50 (VLA)

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Observations held 17/18 January 2005, with MultiPupil Fiber Spectrograph on 6m telescope BTA, 8 exposures, total exposure 5829s seeing ~1".5, spectral resolution R~650 (~8Å at H wavelength)

NGC6946, U-band, CFHT, MegaPrime

(red circle denotes the

coordinates of the X-ray

source, according to

Roberts, Colbert, 2003)

20h 35m 00s.75

+60˚ 11' 30".9

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Data reduction:MPFS-data reduction system developed in IDL environment, prior versions written by V. L. Afanasiev, A. V. Moiseev

Reconsidered and rewritten:

-Extraction using 2 etalon files (different for object and spectral standard)

●Cosmic hits removal (because of non-negligible probability of cosmic particles’

overlapping for different frames for new 2k×2k CCD)

●Added flat field extraction (data cubes rather than initial frames are corrected by flat

fields)

Included:

●Atmospheric dispersion correction (better than 0,1 arcsec accuracy, using spectral

standard)

●Arbitrary correction for interstellar absorption, using CCM (Cardelli, Clayton & Mathis,

1998) absorption curve

●Some other features…

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H / H

[OIII](5007+4959) / H

[SII](6717+6731)/ H

[SII]6717 / [SII]6731

AV

ne, cm-3

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H

[SII] 6717+6731[OIII] 5007+4959

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SCORPIO higher-resolution data (R~1000):

H [OIII]5007+4959

WEWE

Component fluxes and radial velocities

* - red, + - blue

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MF16

NGC 6946 galaxy:

D = 5,5 (from 5,1 to 5,9) Mpc

Scd, active star formation

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MF16

LH = 6 1037 erg/s,

Lemission lines / LH ~ 400

n > 240cm-3 (!)

Pure shock+precursor model (Dopita&Sutherland 1995)

Vshock~400km/s

Shock power must be than:

3 2

383

1

2

101

pre shock shock

pre shock

L V R

nerg s

cm

R=10pc4

Vsh

ock, k

m/s

B/n1/2 =

Vshock , km/s

B/n1/2 =

Page 24: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

The ULX (NGC6946 X-1, X-8, X-11 or ULX-1, ULX-3):

MCD (kT=0.15 keV) + PL (Г = 2.5)L

X=2.5 1039 erg/s (0.5-8.0 keV)

Сhandra observations of NGC 6946 ULX-1 (Roberts, Colbert, 2003)

Page 25: The Optical Counterpart of NGC6946 ULX-1 P. Abolmasov, S. Fabrika, O. Sholukhova, V. Afanasiev Special Astrophysical Observatory, Russia (a peculiar ULX.

HeII

H

[OIII]

H+ radio 20cm

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Hβ [SII](6717+6731)

[OIII](5007+4959)

HeII4686 [NII](6548+6583)

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