Investigation of PAH conditionsin Galactic Planetary Nebulaewith the AKARI/IRC and the Spitzer/IRS

Ryou OhsawaTakashi Onaka, Itsuki Sakon,

Issei Yamamura, Mikako Matsuura, Hidehiro Kaneda, Jeronimo Bernard-Salas,

Oliver Berné, Christine Joblin

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Introduction

dust in the universe

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Introduction

ISM&CSM dust evolutionformation, chemical evolution, destruction, and so on...

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Introduction

Lifecycle of dust grains:dust-formation in evolved starsdust-alternation in various radiation fieldsdust-destruction by radiations/shocks

There are few observational studies.e.g., Giard+(1994), Bernard+(1994), García-Lario+(2003),

Lebouteiller+(2007), Berné+(2008), Kaneda+(2011), Mori+(2011), ...

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Introduction

the UIR bands in planetary nebulaeWhy the UIR bands? Why PNe?

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Why the UIR bands?Polycyclic Aromatic Hydrocarbons

Stochastically heated carbonaceous dust grains

Strong emission bands in the near­ and mid­infrared

Significant variations in the band profiles and strengths

Sensitive to changes in local environments

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Why the UIR bands?

(Peeters+, 2002)

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Why planetary nebulae?Platenary Nebulae

Typical objects showing the PAH features

Drastically changes in radiation fields with evolution

Transitional objects from cirumstellar to interstellar

Hajian+(unpublished)

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Why planetary nebuale?

(Blöcker+, 1995)

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Introduction

Observing the UIR bands in PNe,

We can investigate PAH conditions with different radiation fields.

(CSM environments, extremely hard radiation fields)

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ObservationsPNSPC:Phase 3 spectral observation of Galacitc PNe

IRC grism­spectroscopy (2.5­­5.0μm)

Point source window (Np­window; 1'x1')

Total number of targets = 84 objects(diameter less than 8”, Ks less than 10mJy)

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ObservationsNear­ to mid­IR Spectra of 20 PNe in Milky Way

2.5­5.0μm from the AKARI/IRC(R~120, including the 3.3 and 3.4μm UIR bands)

5.5­14.0μm from the Spitzer/IRS(R~60­100, including the 6.2 to 12.7μm UIR bands)

Data Reduction:AKARI: official pipeline, removing hot pixelsSpitzer: Post­BCD, scaled to NIR­spectra

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Observations

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Observations

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Data analysis

A linear combination of­ free­free, free­bound emissions­ blackbody emission (100K, 200K)

­ line features (H, He, H2, Mg, Ar, Ne, and S)

­ dust features (PAHs and broad features)

Decomposition:

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Results

Define two groups by stellar temperature

1. correlations with radiation fields

2. PAH conditions in PNe

3. aliphatic-aromatic variations

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Radiation FieldsPAH destructions in harsh environments

H II regionNGC 3603Lebouteiller+ (2007)

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Radiation Fields

A steep decline at I([SIV])/I([NeII])~1Destruction of small PAHs??

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Radiation Fields

I([SIV])/I([NeII]) traces evolution,where it lower than ~1

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PAH conditionsSiz

e/ E

xcit

ati

on

Cationic Neutral

7.7μm

6.2μm

11.2μm

3.3μm

(8.6μm)

(e.g., Allamandola+, 1989)

CH

CH

CH

CC

CC

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PAH conditions

(Mori+, 2011)

Diagnostic tools for PAH conditions

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PAH conditions

Preliminary

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Aliphatic-Aromatic

Aliphatic C-H bonds

Aromatic C-H bonds

the 3.4-3.5 μm feature

the 3.3 μm feature

(e.g., Allamandola+, 1989)

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Aliphatic-Aromatic

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Summary

For PNe where [SIV]/[NeII]>1,

1. a large dispersion in size distribution

2. a low ionization factor (??)

3. enhanced aliphatic features

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Problemsscatter or evolution ?

PAH destruction?

PAH hydrogenation?

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Next to do

Another RF estimator where [SIV]/[NeII] > 1[ArV]@7.90, [MgV]@13.1, [NeV]@14.32, etc...

Discussion on broad (amorphous) dust emissionsevolution of amorphous silicate and carbon

Comparing with the FIR colorsusing AKARI MIR & FIR point source catalog

Quantitative discussions on PAH conditionsradiation hardness and G0 with H-coverages and ionizations

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Thank you!

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Appendix

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Appendix

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Appendix

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Appendix

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Appendix