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1 The Red Rectangle Nebula excited by excited species Nadine Wehres, Claire Romanzin, Hans Van Winckel, Harold Linnartz, Xander Tielens
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2 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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3 identify molecules in space and laboratory constraining physical and chemical conditions in RR
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4 The Red Rectangle proto-planetary nebula The observations The laboratory experiments Simulations Conclusion Outline
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5 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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6 The optical emission features of the Red Rectangle Van Winckel et al., A&A, 2002, 390, 147 Extended Red Emission and molecular bands solid state species and gas phase molecules
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7 Molecules in the Red Rectangle Small molecules have been identified: 12 CO; 13 CO; CO 2 ; 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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8 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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9 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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11 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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12 Discharge Source: expanding acetylene (C 2 H 2 ) plasma - Carbon radicals - Transient species: Ions and radicals - Rovibronically excited species Nevertheless, rotationally cold species because of adiabatic expansion
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13 d 3 π g (v’=0) a 3 π u (v”1) d 3 π g (v’=1) a 3 π u (v”=2) C 2 Swan-Band transitions
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14 C2?C2?C2?C2? Peak Positions
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15 Simulations: Rotational contour fitting routines
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16 Simulations: Rotational contour fitting routines
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17 Simulations: Rotational contour fitting routines
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18 Conclusions Unambiguous identification of excited C 2 in the Red Rectangle at several distances in the outflows (at 3”, 6” and 7”) Corresponding with Swan band transitions d 3 π g – a 3 π u (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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19 Work in progress CH + has been identified: T rot of ‘only’ 120 K ± 50 K (Hall et al. (1992), Nature, Vol 358) Why is C 2 warmer – a chemical reason ? statistical equilibrium equations (radiative transfer mechanism) of the excitation pathways of C 2 Formation and destruction scheme of C 2 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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20 Sarre et al., Science 1995, 269, 674 DIBs Red Rectangle Seen in interstellar clouds towards reddened stars
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21 Thank you for your Attention
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