1. 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

2. Large Molecules in CRL 618 Introduction & Motivation –Why CRL 618? Species sought Implications and Conclusions BIMA Array in D-configuration HC 3 NHC 5 N C 6 H CH 3 CNCH 3 C 3 N 34 SO OC 34 S SO 2 MgNC HCOOCH 3 CH 3 CHO CH 3 COOH HCOOH CH 3 CH 2 OH (CH 3 ) 2 O

3. 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 C 6 H 6 –(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)

4. Detected Species CH 3 CN (emission) HC 3 N (absorption)

5. Detected Species HC 5 N (P-Cygni)

6. Species NOT detected C 6 H – Not detected yet very prominent in IRC+10216 OC 34 S SO 2 CH 3 C 3 N – Similar in structure to CH 3 CN HCOOCH 3 CH 3 COOH CH 3 CH 2 OH (CH 3 ) 2 O HCOOH CH 3 CHO } ISOMERS } 34 SO easily detected

7. Implications (C Species) C 6 H – upper limit: 2.5x10 13 cm -2 –Predicted column density: 2.5x10 15 cm -2 (Woods et al. 2003 gas phase formation models) CH 3 C 3 N – upper limit: 3.3x10 13 cm -2 –C 6 H 5 CN & CH 3 C 4 H predicted column densities: 1.5x10 15 cm -2 Based on gas phase formation models, we should have easily detected C 6 H and CH 3 C 3 N.

8. Implications (O species) Conclusions HCOOH, HCOOCH 3 & CH 3 COOH –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.