Upload
deron
View
27
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Evolution of PAH features from proto-PN to planetary nebulae. Ryszard Szczerba N. Copernicus Astronomical Center Toruń, Poland. NCAC TORUN. Collaborators. Mirek Schmidt (CAMK) Natasza Siódmiak (CAMK) Grażyna Stasińska (LUTH Obs. Paris-Meudon) Cezary Szyszka (UMK). NCAC TORUN. - PowerPoint PPT Presentation
Citation preview
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