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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