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The Red Rectangle Nebula
excited by excited species
Nadine Wehres, Claire Romanzin, Hans Van Winckel, Harold Linnartz, Xander Tielens
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The Red Rectangle Nebula
excited by excited species
Nadine Wehres, Claire Romanzin, Hans Van Winckel, Harold Linnartz, Xander Tielens
identify molecules in space and laboratory
constraining physical and chemical conditions in RR
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identify molecules in space and laboratory
constraining physical and chemical conditions in RR
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The Red Rectangle proto-planetary nebulaThe observationsThe laboratory experimentsSimulationsConclusion
Outline
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The Red Rectangle Nebula
Van Winckel et al., A&A, 2002, 390, 147
The post AGB star shows episodic mass loss that still enriches the surrounding nebula and is a great laboratory for ongoing molecule formation
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The optical emission features of the Red Rectangle
Van Winckel et al., A&A, 2002, 390, 147
Extended Red Emission and molecular bandssolid state species and gas phase molecules
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Molecules in the Red Rectangle
Small molecules have been identified:12CO; 13CO; CO2; OH; CH; CH+; CN
Larger species have not been identified sofar, however
Typical PAH emission features are observed:3.3; 6.2; 7.7; 8.6; and 11.3 µm
Silicate emission features
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New Technology Telescope, La Silla, Chile
Obtain complete and medium resolution data-set of spectral progression with distance from central star
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Observations of the Red Rectangle emission features –
Using the New Technology Telescope at La Silla, Chile
Very faint object: long slit spectroscopy for better S/N
Measurements performed for:Central Star 3 “; 6 “; 7 “; 11 “; 14 “; 16 “; and 20 “
Van Winckel et al., A&A, 2002, 390, 147
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Laser Induced Fluorescence Spectroscopy
Search for Carriers
Emission Spectroscopy vs. Absorption Spectroscopy
Open Questions: What is causing the observed features ? Can we simulate the Red Rectangle in the
laboratory? Can we conclude on the actual physical
conditions?
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Discharge Source: expanding acetylene (C2H2) plasma
- Carbon radicals- Transient species: Ions and radicals- Rovibronically excited species
Nevertheless,rotationally cold speciesbecause of adiabaticexpansion
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d3πg (v’=0) a3πu (v”1)
d3πg (v’=1) a3πu (v”=2)
C2 Swan-Band transitions
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C2? C2?
Peak Positions
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Simulations: Rotational contour fitting routines
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Simulations: Rotational contour fitting routines
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Simulations: Rotational contour fitting routines
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Conclusions
Unambiguous identification of excited C2 in the Red Rectangle at several distances in the outflows (at 3”, 6” and 7”)
Corresponding with Swan band transitions
d3πg – a3πu (v”,v’) = (1,0) and (2,1)
Rotational contour simulations show a temperature of about 550 +/- 200 K in the nebula at closer distances
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Work in progress
CH+ has been identified: Trot of ‘only’ 120 K ± 50 K(Hall et al. (1992), Nature, Vol 358)
Why is C2 warmer – a chemical reason ? statistical equilibrium equations (radiative transfer
mechanism) of the excitation pathways of C2 Formation and destruction scheme of C2
Spectral dynamics of other observed bands as function of the distance to the central star.
… and as emission probe for absorption features:
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Sarre et al., Science 1995, 269, 674
DIBs
Red Rectangle
Seen in interstellar clouds towards reddened stars
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Thank you for your Attention
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