Molecular Survival in Planetary Molecular Survival in Planetary Nebulae: Seeding the Nebulae: Seeding the

Chemistry of Diffuse Clouds?Chemistry of Diffuse Clouds?

Jessica L. DoddJessica L. Dodd

Lindsay ZackLindsay Zack

Nick WoolfNick Woolf

Emily TenenbaumEmily Tenenbaum

Lucy M. ZiurysLucy M. Ziurys

The University of ArizonaThe University of Arizona

Departments of Chemistry and AstronomyDepartments of Chemistry and AstronomyThe 65th Ohio State University International Symposium on Molecular Spectroscopy

The Life Cycle of material in the The Life Cycle of material in the Interstellar MediumInterstellar Medium

Dense Clouds – Cold, dense regions of space. 75% of Dense Clouds – Cold, dense regions of space. 75% of molecules found in ISMmolecules found in ISM

Star Formation Regions – Instabilities cause molecular Star Formation Regions – Instabilities cause molecular cloud to collapse, stars/planetary systems formcloud to collapse, stars/planetary systems form

Evolved Stars – stars age and die. Experience mass Evolved Stars – stars age and die. Experience mass loss, molecule-rich circumstellar envelope (over 70 loss, molecule-rich circumstellar envelope (over 70 molecules detected in CSE’s)molecules detected in CSE’s)

Planetary Nebulae (PNe) – Hot, UV emitting central star Planetary Nebulae (PNe) – Hot, UV emitting central star surrounded by neutral and ionized gaseous material. surrounded by neutral and ionized gaseous material. Supplies 86% of material to the ISM.Supplies 86% of material to the ISM.

Diffuse Clouds – material forms diffuse clouds which Diffuse Clouds – material forms diffuse clouds which then collapse to dense clouds.then collapse to dense clouds.

The Molecular Life Cycle

ArizonaObservatoryRadioArizonaObservatoryRadio

ePlanetary Nebulae

Diffuse Clouds Dense Clouds

Star FormationCloud Dispersion

Protoplanetary Disks

Other SolarSystems

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 NebulaThe Helix Nebula

Oldest known PNe, ~11,000 years oldOldest known PNe, ~11,000 years old Molecules have been subject to UV Molecules have been subject to UV

radiation radiation Previously seen CO, HCOPreviously seen CO, HCO++, CN, HCN, , CN, HCN,

HNC HNC (Bachiller et al. 1997)(Bachiller et al. 1997) Recently detected HRecently detected H22CO, c-CCO, c-C33HH22, and C, and C22H H

(Tenenbaum et al. 2009)(Tenenbaum et al. 2009)

HCO+ (J = 1-0)

H2CO (JKaKc = 212-111)

Molecular Observations of PNeMolecular Observations of PNe Need to study more PNeNeed to study more PNe Looking at five new planetary Looking at five new planetary

nebulae nebulae Focusing on HCOFocusing on HCO++ and CS via and CS via

their rotational transitionstheir rotational transitions Using radio telescopes to detect Using radio telescopes to detect

molecular gas phase spectramolecular gas phase spectra HCOHCO++ is wide spread in Helix is wide spread in Helix CS is a tracer of Sulfur chemistry CS is a tracer of Sulfur chemistry

and dense gasand dense gas Not previously detected in any Not previously detected in any

PNePNe HCO+ and CS are abundant in HCO+ and CS are abundant in

molecular cloudsmolecular 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 sourceAge is ~7000 years

CS(3-2)

~1.5'

~1.2'~0.7'

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

CO(2-1)

Huggins & Healy, 1986

Column DensitiesColumn Densities SourceSource Age (years)Age (years) MoleculeMolecule Column Column

Density (p/cc)Density (p/cc)

K4-47K4-47 ~2,000~2,000 HCOHCO++ ~3 x 10~3 x 101212

CSCS 4.2 x 104.2 x 101212

NGC 6537NGC 6537 16001600 HCOHCO++ 1.1 x 101.1 x 101212

CSCS 2.3 x 102.3 x 101212

M2-48M2-48 3,000-5,0003,000-5,000 HCOHCO++ 5.6 x 105.6 x 101212

CSCS 5.4 x 105.4 x 101212

NGC 6720NGC 6720 7,0007,000 HCOHCO++ ~1 x 10~1 x 101212

CSCS ~1 x 10~1 x 101212

Molecules Molecules Survive!Survive!

Molecules exist in small, Molecules exist in small, dense clumps and are dense clumps and are shielded from UV radiationshielded from UV radiation

HST images show dense, HST images show dense, clumpy molecular globulesclumpy molecular globules

Densities between 10Densities between 1055-10-1066 particles/cubic centimeterparticles/cubic centimeter

HST Image

What about What about Diffuse Clouds?Diffuse Clouds?

Lucas and Liszt, 2000-2006Liszt, Lucas, and Pety, 2006

Sixteen molecules have Sixteen molecules have been seen in diffuse been seen in diffuse cloudsclouds

Thirteen can be seen in Thirteen can be seen in all of these sourcesall of these sources

Seen in absorption Seen in absorption against a background against a background sourcesource

Diffuse Clouds vs. Planetary Nebulae

Molecules seen in

Diffuse Clouds

Molecules seen in

Planetary Nebulae

CO, CH, C2H, C3H2, HCO+, CN, HCN, HNC, NH3, OH, H2CO, CS, HCS+, H2S, SO, SiO

CO, C2H, C3H2, HCO+, CN, HCN, HNC, N2H+, OH, H2CO, HCS+,

CS (this work)

CO, HCO+, CN, HCN have been seen in multiple young and old sources C2H and C3H2 have been seen in NGC 7027 and the Helix H2CO and HNC have been seen in old sources HCS+, N2H+, and OH have been seen in NGC 7027

ConclusionsConclusions Planetary Nebula age does not appear to matter.Planetary Nebula age does not appear to matter. Molecules can definitely survive the PNe stageMolecules can definitely survive the PNe stage If molecules can survive the intense radiation in If molecules can survive the intense radiation in

a PNe for 12,000 years, they can survive in the a PNe for 12,000 years, they can survive in the ISM and be recycled into Diffuse Clouds!ISM and be recycled into Diffuse Clouds!

The molecules that do survive this stage seed The molecules that do survive this stage seed the chemistry that is seen in Diffuse Cloudsthe chemistry that is seen in Diffuse Clouds

Greater chemical complexity in the ISM can be Greater chemical complexity in the ISM can be achieved, not starting with atomsachieved, not starting with atoms

Future DirectionsFuture 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 speciesDifferent chemical species Studies of VY Canis Majoris, an oxygen rich star, Studies of VY Canis Majoris, an oxygen rich star,

reveal a large content of sulfur-bearing moleculesreveal 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