Gdańsk 2005 1

Evolution of PAH features from Evolution of PAH features from proto-PN to planetary nebulaeproto-PN to planetary nebulae

Ryszard Szczerba

N. Copernicus Astronomical Center

Toruń, Poland

2 Gdańsk 2005

Collaborators

•Mirek Schmidt (CAMK)

•Natasza Siódmiak (CAMK)

•Grażyna Stasińska (LUTH Obs. Paris-Meudon)

•Cezary Szyszka (UMK)

NCACTORUN

Gdańsk 2005 3

NCACTORUN

Sir Frederick William Herschel

• F.W. Herschel (1738 -1822) was born in Hanover.

• From 1757 he lived in England.

• A musician and an astronomer.

• In 1781 he discovered Uranus;

• He created catalogs of double stars and nebulae;

• In 1800 he discovered infrared radiation.....

Gdańsk 2005 4

Discovery of IR radiation. NCACTORUN

Gdańsk 2005 5

Dust - CAMK PAN

TORUN

INTRODUCTION: Existence of solid particles was demonstrated by Trumpler (1930) through the measurements of color excess between the photographic (~4300 A) and V (~5500 A) magnitudes. By the end of 30’s, a -1 extinction law in the wavelength range 1-3 m-1 had been established. Greenstein (1938) proposed a power-law size distribution of dust grains (dn(a)/da ~ a-3.6!) in the size range 80A<a<1 cm to explain the -1 extinction law. The discovery of interstellar polarization stimulated Cayrel & Schatzman (1954) to consider graphite as interstellar dust component (strong optical anisotropy).

Gdańsk 2005 6

Extinction lawNCAC

TORUN

R=A(V)/E(B-V) N(H)/E(B-V)~5.8 1021 cm-2 (Bohlin et al. 1978)

Gdańsk 2005 7

graphitic structureNCAC

TORUN

Graphite is highly anisotropic material

Gdańsk 2005 8

Dust - CAMK PAN

TORUN

INTRODUCTION cont.: Hoyle & Wickramasinghe (1962) proposed that graphite could form in the atmospheres of cool C-stars and be ejected into ISM.In 1960’s and early 1970’s UV space missions allowed to determine extinction law in the wavelength range 0.2-10 m-1.The presence of 2200 A interstellar extinction bump (Stecher 1965) was interpreted as reinforcement of the graphite proposal. However, exact nature of this bump still remains unidentified! Gilman (1969) proposed that grains around M-type stars are mainly silicates (Al2SiO3, Mg2SiO4, ...).Interstellar silicates were first detected in emission in Orion Nebula (Stein & Gillett 1969) and in absorption toward the Galactic Center (Hackwell et al. 1970).

Gdańsk 2005 9

amorphous silicate featuresNCAC

TORUN

9.7 m Si-O stretching mode

18 m O-Si-O bending mode

Dust thermal emission:

m] x T[K] = 3000

ISM: T~20 K; max~150 m

CS: T~150 K; max~20 m

Gdańsk 2005 10

Dust - CAMK PAN

TORUN

INTRODUCTION cont.: In mid-1970’s the interstellar extinction curve had been determined in the whole wavelengths range & the main dust components had been determined (graphite & silicates).

Mathis et al. (1977) proposed a model of interstellar dust composed of silicates and graphite with grain size distribution dn(a)/da ~ a-3.5 in the size range 50 A < a < 0.25 m (MRN model):MRN model is very successful: 1250 citations in ADS (56 in 2005).

Gdańsk 2005 11

MRN model of interstellar dustNCAC

TORUN

Silicates & graphite:

•dn(a)/da ~ a-3.5

•50A<a<0.25 m

Gdańsk 2005 12

Dust - CAMK PAN

TORUN

Very Small Grains (VSGs): Donn (1968) proposed that particles like Policyclic Aromatic Hydrocarbons (PAHs) may be responsible for the UV interstellar extinction. Greenberg (1968) first pointed out that VSGs with a heat content comparable to the energy of a single photon, cannot be characterized by an equilibrium temperature but are subject to fluctuations in temperature.

Observational arguments that VSGs are present in Interstellar Space:

Gdańsk 2005 13

VSGs in Inter- & CS-stellar Space

CAMK PAN

TORUN

1) The discovery of presolar nanodiamonds (Lewis et al. 1987) and TiC nanocrystals (Bernatowicz et al. 1996).

2) The ubiquitous distinctive set of „UIR” emission bands @ 3.3, 6.2, 7.7, 8.6 and 11.3 m (UIR bands were discoverd first by Gillet et al. (1973) in planetary nebulae). This emission can be explained by transiently heating PAHs (e.g model of Li & Draine 2001 for ISM, where UIRs account ~20% of the total power radiated by dust).

3) The mid-IR emission at<60 m, discovered by IRAS (12 & 25 m bands) and confirmed by COBE-DIRBE and IRTS observations (see e.g. Draine 2003 and references therein). This emission can be explained also by transiently heating PAHs (Weingartner & Draine 2001).

Gdańsk 2005 14

Presolar grains from meteoritesNCAC

TORUN

Gdańsk 2005 15

Presolar grainsNCAC

TORUN

„typical” dust particle (top)

Presolar SiC (right)

Gdańsk 2005 16

NCACTORUN

reflection nebulae

PAH features in:

Gdańsk 2005 17

PAHs: aromatic rings + HNCAC

TORUN

Leger & Puget (1984)Allamandola et al. (1989)

•C-H „stretch” @ 3.3m•C-C „stretch” @ 6.2 m•C-C „stretch” @ 7.7 m•C-H in-plane „bend” @ 8.6m•C-H out of plane „bend” @ 11.3 m for mono H@ 12.0 m for duo H@ 12.7 m for trio H@ 13.6 m for quartet H

•aliphatic (chain-like) C-H „stretch” @ 3.4 m

Gdańsk 2005 18

graphitic structureNCAC

TORUN

Graphite is highly anisotropic material

Gdańsk 2005 19

PAH features in:NCAC

TORUN

galaxies (top)

HII regions (right)

Gdańsk 2005 20

NCACTORUN

The detection by ISO ofcrystalline silicates marks begining of: ASTROCRYSTALOGRAPHY

PAH features in:

[WR] planetary nebulae: Szczerba et al. (2001)

Gdańsk 2005 21

The mid-IR emission at <60mNCAC

TORUN

Observed (left)

Model (bottom) Weigartner & Draine (2001)

For T=15-25 K, emission from „large” grains is lower by several orders of magnitude!

Gdańsk 2005 22

VSGs in Inter- & CS-stellar Space

CAMK PAN

TORUN

4) The far-UV extinction rise (Donn 1968 – see also Kruegel 2003). Dust grains absorbs and scatters light most effectively @~2a.

5) The ”anomalous” Galactic foreground microwave emission in th 10-100 GHz region. Discovered during studies of CMB is probably due to the fats rotation fo nanoparticles (Draine & Lazarian 1998).

6) The Extended Red Emission (ERE), first discovered in Red Rectangle (Schmidt et al. 1980). The ERE is attributed to PL of (possibly?) crystalline nano-silicon clusters (Witt et al. 1998).

7) The photoelectric heating of the diffuse ISM. VSGs are more efficient in heating the gas than large grains. VSGs are responsible for > 95% of the total photoelectric heating of the gas in ISM (Weingartner & Draine 2001) .

Gdańsk 2005 23

PAHs in LMC: Ciska Markwick-Kemper et al.

Gdańsk 2005 24

PAHs in LMCNCAC

TORUN

Gdańsk 2005 25

3.3 & 3.4 m bands in PN: BD+ 30 3639NCAC

TORUN

Gdańsk 2005 26

7.7 & 8.6 m bands in PN: BD+ 30 3639NCAC

TORUN

Gdańsk 2005 27

6.2, 7.7 & 8.6 m bands in PN: BD+ 30 3639NCAC

TORUN

Gdańsk 2005 28

7.7 m band shape in proto-PN:NCAC

TORUN

Gdańsk 2005 29

6.2 m band shape in galactic objectsNCAC

TORUN

Gdańsk 2005 30

3.3 m C-H stretching modeNCAC

TORUN

Gdańsk 2005 31

6.2 m C-C stretching modeNCAC

TORUN

Gdańsk 2005 32

7.7 m C-C stretching modeNCAC

TORUN

Gdańsk 2005 33

Ratio of 7.7 an 6.2 m bandsNCAC

TORUN

Gdańsk 2005 34

8.6 m C-H in-plane bending modeNCAC

TORUN

Gdańsk 2005 35

Correlation between 3.3 & 6.2 m bandsNCAC

TORUN

Gdańsk 2005 36

Correlation between 7.7 & 8.6 m bandsNCAC

TORUN

Gdańsk 2005 37

3.3 m band in proto-PN:NCAC

TORUN

Gdańsk 2005 38

6.2 m band in proto-PN:NCAC

TORUN

Gdańsk 2005 39

7.7 m band in proto-PN:NCAC

TORUN

Gdańsk 2005 40

8.6 m band in proto-PN:NCAC

TORUN

Gdańsk 2005 41

•Stasińska, Szczerba, Schmidt, Siódmiak

„Post-AGB objects as testbeds of nuclosynthesis in AGB stars”

submitted to A&A• We can investigate chemistry in objects with smaller mass

• C: smaller uncertainty than in PNe

•....

NCACTORUN

Gdańsk 2005 42

CNO in post-AGB objectsNCAC

TORUN

Gdańsk 2005 43

CNO in post-AGB objectsNCAC

TORUN