Molecular Survival in Planetary Nebulae: Seeding the Chemistry of Diffuse Clouds? Jessica L. Dodd Lindsay Zack Nick Woolf Emily Tenenbaum Lucy M. Ziurys The University of Arizona Departments of Chemistry and Astronomy The 65th Ohio State University International Symposium on Molecular Spectroscopy

The Life Cycle of material in the Interstellar Medium Dense Clouds – Cold, dense regions of space. 75% of molecules found in ISM Dense Clouds – Cold, dense regions of space. 75% of molecules found in ISM Star Formation Regions – Instabilities cause molecular cloud to collapse, stars/planetary systems form Star Formation Regions – Instabilities cause molecular cloud to collapse, stars/planetary systems form Evolved Stars – stars age and die. Experience mass loss, molecule-rich circumstellar envelope (over 70 molecules detected in CSE ’ s) Evolved Stars – stars age and die. Experience mass loss, molecule-rich circumstellar envelope (over 70 molecules detected in CSE ’ s) Planetary Nebulae (PNe) – Hot, UV emitting central star surrounded by neutral and ionized gaseous material. Supplies 86% of material to the ISM. Planetary Nebulae (PNe) – Hot, UV emitting central star surrounded by neutral and ionized gaseous material. Supplies 86% of material to the ISM. Diffuse Clouds – material forms diffuse clouds which then collapse to dense clouds. Diffuse Clouds – material forms diffuse clouds which then collapse to dense clouds.

The Molecular Life Cycle e Planetary Nebulae Diffuse Clouds Dense Clouds Star Formation Cloud Dispersion Protoplanetary Disks Other Solar Systems Evolved Stars

Planetary Nebulae Majority of stars (from ~0.5-8 M  ) will become PNe Hot (~100,000 to 400,000 K), UV emitting central star surrounded by gaseous material from molecule rich Circumstellar Envelope Molecular material is flowing outward but being ionized by central star Initially thought that all molecular matter would be destroyed in PNe, photodissociated by central star Ionized material accounts for a small percentage of the old stellar mass. Where is the rest? 86% of material going into ISM! Can molecules survive in this harsh environment?

The Helix Nebula Oldest known PNe, ~11,000 years old Oldest known PNe, ~11,000 years old Molecules have been subject to UV radiation Molecules have been subject to UV radiation Previously seen CO, HCO +, CN, HCN, HNC (Bachiller et al. 1997) Previously seen CO, HCO +, CN, HCN, HNC (Bachiller et al. 1997) Recently detected H 2 CO, c-C 3 H 2, and C 2 H (Tenenbaum et al. 2009) Recently detected H 2 CO, c-C 3 H 2, and C 2 H (Tenenbaum et al. 2009)

HCO + (J = 1-0)

H 2 CO (J KaKc = )

Molecular Observations of PNe Need to study more PNe Need to study more PNe Looking at five new planetary nebulae Looking at five new planetary nebulae Focusing on HCO + and CS via their rotational transitions Focusing on HCO + and CS via their rotational transitions Using radio telescopes to detect molecular gas phase spectra Using radio telescopes to detect molecular gas phase spectra HCO + is wide spread in Helix HCO + is wide spread in Helix CS is a tracer of Sulfur chemistry and dense gas CS is a tracer of Sulfur chemistry and dense gas Not previously detected in any PNe Not previously detected in any PNe HCO+ and CS are abundant in molecular clouds HCO+ and CS are abundant in molecular clouds Photos courtesy of the Arizona Radio Observatory and Dave Harvey

Planetary Nebula K4-47 Age ~2000 years old HCO + (1-0) CO(1-0)CS(3-2) CS(5-4)

The Red Spider Nebula, NGC 6537 HST Image HCO + (1-0) Age is 1600 years old. Central star is one of the hottest white dwarfs known T* ~ 400,000 K HCO + (3-2) CS(5-4) CS(3-2)

Planetary Nebula M2-48 Age is estimated to be between 3000 and 5000 years old. HCO + (1-0) HCO + (3-2) CS(3-2) CS(5-4)

The Ring Nebula, NGC 6720 HCO + (1-0) HST Image Old source Age is ~7000 years CS(3-2) ~1.5' ~1.2' ~0.7' CO(2-1) Huggins & Healy, 1986

Column Densities Source Source Age (years) Molecule Column Density (p/cc) K4-47~2,000 HCO + HCO + ~3 x CS CS 4.2 x NGC HCO + HCO x CS CS 2.3 x M2-483,000-5,000 HCO + HCO x CS CS 5.4 x NGC ,000 HCO + HCO + ~1 x CS CS ~1 x 10 12

Molecules Survive!  Molecules exist in small, dense clumps and are shielded from UV radiation  HST images show dense, clumpy molecular globules  Densities between particles/cubic centimeter HST Image

What about Diffuse Clouds? Lucas and Liszt, Liszt, Lucas, and Pety, 2006 Sixteen molecules have been seen in diffuse clouds Sixteen molecules have been seen in diffuse clouds Thirteen can be seen in all of these sources Thirteen can be seen in all of these sources Seen in absorption against a background source Seen in absorption against a background source

Diffuse Clouds vs. Planetary Nebulae Molecules seen in Diffuse Clouds Molecules seen in Planetary Nebulae CO, CH, C 2 H, C 3 H 2, HCO +, CN, HCN, HNC, NH 3, OH, H 2 CO, CS, HCS +, H 2 S, SO, SiO CO, C 2 H, C 3 H 2, HCO +, CN, HCN, HNC, N 2 H +, OH, H 2 CO, HCS +, CS (this work) CO, HCO +, CN, HCN have been seen in multiple young and old sources C 2 H and C 3 H 2 have been seen in NGC 7027 and the Helix H 2 CO and HNC have been seen in old sources HCS +, N 2 H +, and OH have been seen in NGC 7027

Conclusions Planetary Nebula age does not appear to matter. Planetary Nebula age does not appear to matter. Molecules can definitely survive the PNe stage Molecules can definitely survive the PNe stage If molecules can survive the intense radiation in a PNe for 12,000 years, they can survive in the ISM and be recycled into Diffuse Clouds! If molecules can survive the intense radiation in a PNe for 12,000 years, they can survive in the ISM and be recycled into Diffuse Clouds! The molecules that do survive this stage seed the chemistry that is seen in Diffuse Clouds The molecules that do survive this stage seed the chemistry that is seen in Diffuse Clouds Greater chemical complexity in the ISM can be achieved, not starting with atoms Greater chemical complexity in the ISM can be achieved, not starting with atoms

Future Directions Continue working on Helix (~11,000 yrs old) Continue working on Helix (~11,000 yrs old) Look in the Dumbbell Nebula (~10,000 yrs old) Look in the Dumbbell Nebula (~10,000 yrs old) Different chemical species Different chemical species Studies of VY Canis Majoris, an oxygen rich star, reveal a large content of sulfur-bearing molecules Studies of VY Canis Majoris, an oxygen rich star, reveal a large content of sulfur-bearing molecules Carbon rich PNe vs. Oxygen rich PNe? Carbon rich PNe vs. Oxygen rich PNe?

Acknowledgements Dr. Ziurys, Dr. Woolf Dr. Emily Tenenbaum, Lindsay Zack The rest of the Ziurys Group Arizona Radio Observatory Engineers, Operators NASA and NSF for funding