The Herschel view of massive star nebulaeVamvatira-Nakou et al., in prep “Herschel meeting” - 5 June 2012 Leuven . 15 The nebula around WRAY 15-751 PACS photometric maps 70 μm

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The Herschel view of massive star nebulae

C. Vamvatira-Nakou1, D. Hutsemékers1, P. Royer2, Y. Nazé1, P. Magain1,

G. Rauw1, K. Exter2, M. A. T. Groenewegen3 & C. Waelkens2

1 Université de Liège, Belgium

2 Katholieke Universiteit Leuven, Belgium

3 Royal Observatory of Belgium

“Herschel meeting” - 5 June 2012 Leuven

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Introduction

Part of the MESS (Mass-loss of Evolved StarS) Herschel Guaranteed Time Key ProgrammePart of the MESS (Mass-loss of Evolved StarS) Herschel Guaranteed Time Key Programme=> Study the circumstellar matter in evolved objects => Study the circumstellar matter in evolved objects ((Groenewegen, et al. 2011, A&A, 526, 162)Groenewegen, et al. 2011, A&A, 526, 162)

Scientific Aims of our project:Scientific Aims of our project:

Study of the dust and the gas in the circumstellar environment of evolved massive stars Study of the dust and the gas in the circumstellar environment of evolved massive stars (LBVs and WR Stars)(LBVs and WR Stars)

• Information on the dust shells (size, structure)Information on the dust shells (size, structure)

• Determination of dust properties (temperature, mass, composition, dust grain size)Determination of dust properties (temperature, mass, composition, dust grain size) • Determination of gas chemical abundances and photo-dissociation regionDetermination of gas chemical abundances and photo-dissociation region (PDR) properties(PDR) properties

• Estimation of dust location with respect to the gasEstimation of dust location with respect to the gas

• Study of the mass-loss historyStudy of the mass-loss history


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Introduction

Circumstellar environment of evolved Circumstellar environment of evolved massive stars

Luminous Blue Variables (S Doradus variables)Luminous Blue Variables (S Doradus variables)

Evolved, massive, very luminous, unstable hot supergiants in the upper left of the HR diagram, Evolved, massive, very luminous, unstable hot supergiants in the upper left of the HR diagram, suffer irregular eruptions, precursors of WR starssuffer irregular eruptions, precursors of WR stars

Photometric variability: from giant eruptions (Photometric variability: from giant eruptions (≥2 mag) to microvariations ≥2 mag) to microvariations ( (≤0.1 mag) ≤0.1 mag)

Often surrounded byOften surrounded by ejected nebulaeejected nebulae::

- Diameter: 0.5 - 2 pc - Expansion velocity: 25 - 140 km s- Diameter: 0.5 - 2 pc - Expansion velocity: 25 - 140 km s-1-1

- Dynamical age: 5×10- Dynamical age: 5×1033 - 5×10 - 5×1044 yr - Morphology: axisymmetric - mildly to yr - Morphology: axisymmetric - mildly to extremely bipolar or elliptical extremely bipolar or elliptical- Spectra: typical nebular emission lines- Spectra: typical nebular emission lines

- Contain significant amounts of dust - Contain significant amounts of dust and few of them COand few of them CO


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Introduction

Circumstellar environment of evolved Circumstellar environment of evolved massive stars

Wolf-Rayet StarsWolf-Rayet Stars

Hot, luminous objects (‘bare cores’) with strong broad emission lines due to stellar windsHot, luminous objects (‘bare cores’) with strong broad emission lines due to stellar winds

Spectra: strong broad emission lines Spectra: strong broad emission lines

May be surrounded by May be surrounded by ejected nebulaeejected nebulae: :

- Bigger than LBVs nebulae- Bigger than LBVs nebulae

- in the optical: nebulae around one third of the Galactic WR stars (Marston 1997) - in the optical: nebulae around one third of the Galactic WR stars (Marston 1997)

- WR Ring nebulae believed to represent material ejected during the RSG or LBV phase that- WR Ring nebulae believed to represent material ejected during the RSG or LBV phase that is photo-ionized by the WR star and interacts with the ISMis photo-ionized by the WR star and interacts with the ISM


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NameName central starcentral star PACS (imag.)PACS (imag.) PACS (spec.)PACS (spec.)

AG Car AG Car LBV LBV X X X X HR Car HR Car LBVLBV X X XX WRAY 15-751WRAY 15-751 LBVLBV XX X X G79.29+0.46 G79.29+0.46 LBVLBV X X X X

He 3-519He 3-519 LBV cand.LBV cand. X X

HD 168625 HD 168625 LBV cand. LBV cand. X X X X

M 1-67 M 1-67 WRWR X X X X NGC 6888 NGC 6888 WRWR XX

NGC 6164/5 NGC 6164/5 Of?pOf?p XX XX

Observations with Herschel

List of targets

X => remaining


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The nebula around the LBV AG Car

70 μm 100 μm 160 μm

Diameter: 45 arcsec



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70 μm 100 μm 160 μm

Size: 60x100 arcsec


The nebula around the LBV HR Car


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70 μm 100 μm 160 μm

Diameter: 240 arcsecSecond Shell: 430 arcsec


The nebula around the LBV G 79.29+0.46


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G79.29+0.46 Spitzer IRAC & MIPS

imaging

F. M. Jiménez-Esteban,J. R. Rizzo & A. Palau2010


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70 μm 100 μm 160 μm

Diameter: 80 arcsec


The nebula around the LBV candidate He 3-519


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70 μm 100 μm 160 μm

Size ~ 37 arcsec


The nebula around the LBV candidate HD 168625

Size ~ 37 arcsec


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70 μm 100 μm 160 μm

Diameter: 125 arcsec


The WR nebula M 1-67


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Diagonal size ~18 arcmin

B=70 μmG=100 μmR=160 μm


The WR nebula NGC 6888


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The nebula around WRAY 15-751

PACS photometric maps

70 μm 100 μm 160 μm

Vamvatira-Nakou et al., in prep


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PACS photometric maps

70 μm 100 μm 160 μm

Hα



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Deconvolution – MSC method


Ring nebula Radius: ~ 18 arcsec

(Magain et al. 1998)

70 μm 100 μm 160 μm



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MADmap algorithm

Second shell ~ 2.1 ⨯ 2.5 arcmin


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PACS spectrum (SED mode)




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Modeling the dust nebula (2-Dust)


rin

= 7 arcsec rin

= 0.20 pcr

out = 3 ⨯ r

in D=6 kpc => r

out = 0.60 pc

PACS image 2-Dust synthetic image Assumptions:

- spherical symmetry- dust density in the inner nebula ~r-2

70 μm

100 μmWRAY 15-751 is a variable star

--> Sterken et al. 2008

1989: minimum hot phase 2008: maximum cooler phase

radiative transfer code,

Ueta & Meixner 2003)


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Best fits of the IRAS/ISO data

assuming: R*/T

eff= 80/18000 and

- αmin

/αmax

= 0.05/1.5 (solid line) - α

min/α

max= 0.2/0.5 (dashed line)

Best fits of the AKARI/Herschel data (epoch 2007-2010)

assuming: - R*/T

eff=320/9000 and

- αmin

/αmax

= 0.05/1.5 (solid line) - α

min/α

max= 0.2/0.5 (dashed line)

- R*/T

eff=240/9000 and α

min/α

max=0.2/0.5 (dotted line)

Sterken et al. 2008 for the 2007-1010 epoch

(epoch 1983-1996)

Bump at ~10 μm: silicates + tiny, warm, out of equilibrium carbon grains (Voors et al. 2000)

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- we used silicate dust with the highest IR available absorptivity (O-rich silicates with Fe inclusion)

- adopt an average bulk density ρ = 3.5 g cm-3

- using αmin

=0.2 <α < αmax

=0.5 We fitted - IRAS/ISO data with R*/T

eff= 80/18000

- AKARI/Herschel data with R*/T

eff=320/9000

-The observed dust emission cannot be reproduced when using the low luminosity stellarparameters R

*/T

eff=240/9000 (Sterken et al. 2008, for the 2007-2010 epoch)

- Mdust

=4.5±0.5 10-2 Mꙩ and Tdust varies from 95K (rin) to 66K (rout) - the second shell has Tdust ~45K and Mdust~3 10-2 Mꙩ

The dust emission does not significantly change from 1996 to 2010 The stellar variations occur at constant luminosity, as found in several LBVs

Total ejected dust mass ~ 0.07 Mꙩ


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Photo-ionisation region properties

===> emission lines [N===> emission lines [NIIII] 122 & 205 μm, [N] 122 & 205 μm, [NIIIIII] 58 μm, [O] 58 μm, [OIIIIII] 88 μm] 88 μm

->-> electron density diagnostics : - [N electron density diagnostics : - [NIIII] 122/205 μm (this study)] 122/205 μm (this study) - - [S [SIIII] 6716/6731 ] 6716/6731 ÅÅ (Hutsem (Hutseméékers & Van Drom, 1991,kers & Van Drom, 1991, => => nnee = 279 = 279 ± 83 cm± 83 cm-3-3 (T(Tee=10,000 K)=10,000 K) Garcia-Lario et al., 1998) Garcia-Lario et al., 1998)

->-> abundance abundance N/ON/O from [N from [NIIIIII]/[O]/[OIIIIII] : N/O = N] : N/O = N++++/O/O++++ = 1.0 = 1.0

-> -> abundance abundance N/HN/H from [N from [NIIIIII], [N], [NIIII], Ηα : ], Ηα : N/H = (NN/H = (N+++N+N++++)/H)/H+ + = 3.3 = 3.3 ⨯⨯ 10 10-4-4 photo-ionisation time scale ~ 440yr => stellar variations can be neglected herephoto-ionisation time scale ~ 440yr => stellar variations can be neglected here

->-> Q Q0 0 (from Hα flux and radio flux)(from Hα flux and radio flux) => => early B starearly B star (agreement with spectral type) (agreement with spectral type)

->-> R Rss ~ R ~ R

neb. Hαneb. Hα => => ionization bounded nebulaeionization bounded nebulae (agreement with PDR lines) (agreement with PDR lines)

->-> MMionised ionised ~ 1.6-2.1 M ~ 1.6-2.1 Mꙩꙩ (for n(for n

HeHe/n/nHH=0.2-0.4, Lamers et al. 2001)=0.2-0.4, Lamers et al. 2001)


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Photo-dissociation region (PDR)

===> emission lines [O===> emission lines [OII] 63 & 145 μm, [C] 63 & 145 μm, [CIIII] 158 μm ] 158 μm

PDR regions in nebulaePDR regions in nebulae around:around: the LBV HR Car (Umana et al. 2009), the LBV HR Car (Umana et al. 2009), the LBV candidate HD 168625 (Umana et al. 2010)the LBV candidate HD 168625 (Umana et al. 2010)

->-> contribution from H contribution from HIIII region to [C region to [CIIII] flux:] flux: using measurements of the [Nusing measurements of the [NIIII] 122 μm line, which arises exclusively in the ionised gas] 122 μm line, which arises exclusively in the ionised gas (Goicoechea et al. 2004)(Goicoechea et al. 2004)

->-> atomic mass estimation: atomic mass estimation:

M(MM(Mꙩꙩ) = 7x10) = 7x106 6 FFPDRPDR(CII) (CII) dd22/ X/ X

c c (Fong et al. 2001, (Fong et al. 2001,

Castro-Carrizo et al. 2001)Castro-Carrizo et al. 2001)

=> => MMatomicatomic~ 0.05 M~ 0.05 Mꙩꙩ (assuming solar X(assuming solar X

c c ) )

(10-15 W/m2) (

10-1

5 W

/m2 )


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Nebula around the LBV WRAY 15-751Nebula around the LBV WRAY 15-751::

Ring dust nebula with Ring dust nebula with r r ~ 18 arcsec (= 0.5 pc), ring width ~ 12 arcsec (= 0.35 pc) (~ 18 arcsec (= 0.5 pc), ring width ~ 12 arcsec (= 0.35 pc) (DD = 6 = 6 ± 1 kpc)± 1 kpc)

=>=> Kinematic age ~Kinematic age ~

1.3 10⨯ 1.3 10⨯ 4 4 years (expansion velocity 26 km/s, Hutsemekers years (expansion velocity 26 km/s, Hutsemekers

& Van Drom 1992) & Van Drom 1992) => M=> M

dustdust ~ 4.5 ± 0.5 10⨯ ~ 4.5 ± 0.5 10⨯ -2 -2 MMꙩꙩ , , TTdustdust = 95 K at r = 95 K at rinin to 66 K at r to 66 K at r

outout

Second bigger, fainter shell detected for the first time with Second bigger, fainter shell detected for the first time with rr ~ 70 arcsec (= 2 pc) ~ 70 arcsec (= 2 pc) => Kinematic age ~ 7.5 10⨯=> Kinematic age ~ 7.5 10⨯ 4 4 years (assuming same expansion velocity)years (assuming same expansion velocity)

=> M=> Mdustdust ~ 3 10⨯ ~ 3 10⨯ -2 -2 MMꙩ ꙩ , , TTdustdust = 45 K = 45 K

No other dust feature on the spectrum apart from the dust continuumNo other dust feature on the spectrum apart from the dust continuum

Forbidden emission lines detected: [NForbidden emission lines detected: [NIIII] 122 & 205 μm, [N] 122 & 205 μm, [NIIIIII] 58 μm, [O] 58 μm, [OIIIIII] 88 μm, [O] 88 μm, [OII] 63 & 145 μm,] 63 & 145 μm, [C[CIIII] 158 μm => ] 158 μm => The gas is highly ionisedThe gas is highly ionised

Lines Lines coming from the Hcoming from the HIIII region and lines coming from the PDR region region and lines coming from the PDR region

Net improvement of physical propertiesNet improvement of physical properties

Conclusions

Nebula around the LBV WRAY 15-751:Nebula around the LBV WRAY 15-751: • Ring dust nebula with Ring dust nebula with r r ~ 18 arcsec (= 0.5 pc), ring width ~ 12 arcsec (= 0.35 pc) ~ 18 arcsec (= 0.5 pc), ring width ~ 12 arcsec (= 0.35 pc) (distance = 6 (distance = 6

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Working Plan

PACS data (imaging and spectroscopy) + data in other wavelengths (optical, radio ...) + data in other wavelengths (optical, radio ...)

• Morphology of the nebulae Morphology of the nebulae

Dust emission modelling => estimation of the dust properties Dust emission modelling => estimation of the dust properties

Photo-ionisation region and PDR characteristics Photo-ionisation region and PDR characteristics

Gas abundances estimationsGas abundances estimations

Estimation of the dust and the gas massEstimation of the dust and the gas mass

• Study of the mass-loss history Study of the mass-loss history


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T h a n k y o u

The Herschel view of massive star nebulaeVamvatira-Nakou et al., in prep “Herschel meeting” - 5 June 2012 Leuven . 15 The nebula around WRAY 15-751 PACS photometric maps 70 μm

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