Transcript CRLPresentation.ppt

A Survey of Large Molecules
toward the Protoplanetary Nebula
CRL 618
Anthony J. Remijan
NASA/GSFC
Friedrich Wyrowski
Max-Planck-Institut fur Radioastronomie
Douglas Friedel, David Meier & Lewis Snyder
University of Illinois
June 10, 2005, ApJ, 626, 233
Large Molecules in CRL 618
• Introduction & Motivation
– Why CRL 618?
• Species sought
HC3N
HC5N
C6H
CH3CN CH3C3N
34SO
OC34S
MgNC
SO2
HCOOCH3 CH3CHO
CH3COOH HCOOH
CH3CH2OH (CH3)2O
• Implications and
Conclusions
BIMA Array in D-configuration
Introduction and Motivation
• Carbon rich evolved PPN
with a thick molecular
envelope
• Actual physical structure very
complex
– (Pardo et al. 2005, in press)
• First report of C6H6
– (Cernicharo et al. 2001)
• The chemistry was more
similar to the ISM than other
PPNe.
– (Bujarrabal et al. 1988)
HST image of the high velocity bipolar outflows.
sulphur – red; green - hydrogen; blue-green –
oxygen; blue is continuum. (Trammel 2000)
Detected
Species
CH3CN
(emission)
HC3N
(absorption)
Detected
Species
HC5N
(P-Cygni)
Species NOT detected
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C6H – Not detected yet very prominent in IRC+10216
OC34S
34SO easily detected
SO2
CH3C3N – Similar in structure to CH3CN
HCOOCH3
CH3COOH ISOMERS
CH3CH2OH
ISOMERS
(CH3)2O
HCOOH
CH3CHO
}
}
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Implications (C Species)
• C6H – upper limit: 2.5x1013 cm-2
– Predicted column density: 2.5x1015 cm-2
(Woods et al. 2003 gas phase formation
models)
• CH3C3N – upper limit: 3.3x1013 cm-2
– C6H5CN & CH3C4H predicted column
densities: 1.5x1015 cm-2
Based on gas phase formation models,
we should have easily detected C6H and
CH3C3N.
Implications (O species)
Conclusions
• HCOOH, HCOOCH3 & CH3COOH
– Are not taken into account in current formation models
– The non-detection implies the chemistry present in
CRL 618 is not conducive to forming large O-bearing
species.
• CRL 618 is very good at producing large carbon
chain species but the non-detections need to be
considered in future formation models.
• RISK: Detections of new circumstellar molecules
may in actuality be rotational transitions of
vibrational states of simpler species.