the 69 th international symposium on molecular spectroscopy june 19, 2014 comparative chemistry of...

The 69th International Symposium on Molecular Spectroscopy June 19, 2014

Comparative Chemistry of Planetary Nebulae:

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Jessica L. EdwardsLucy M. ZiurysThe University of ArizonaDepartments of Chemistry and Astronomy

The Role of the Carbon to Oxygen Ratio


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What is a Planetary Nebula?

• Planetary Nebulae (PNe) are one of the final stages of a star’s life

• As stars age, nucleosynthesis becomes more unstable causing these evolved stars to experience significant mass loss

• Creates molecule-rich circumstellar envelope

• Carbon-rich (C/O>1), Oxygen-rich (C/O<1), or in between (C≈O), depending on the stellar mass

Not this


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What is a Planetary Nebula? • Carbon-rich stars (C/O>1)

are formed via the triple-alpha process

• More massive (≈4-8 Mʘ) stars can undergo hot-bottom burning which activates the CNO cycle and lowers the C/O ratio to near 1, or even convert the star back to an Oxygen-rich object (C/O<1)


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What is a Planetary Nebula? • The C/O ratio determines

the types of molecules observed in these circumstellar envelopes

• Circumstellar envelope detaches, material flows outward, and becomes a planetary nebula (UV radiation)

This!


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Molecular Studies of PNe

Photo courtesy: Dave Harvey

• Every frequency range available on both of the Arizona Radio Observatory Telescopes from 65 GHz – 720 GHz

• >2,500 hours of observing time

ARO Band 9Receiver

http://aro.as.arizona.edu/images/smt/smt_harvey_2.jpg

http://aro.as.arizona.edu/images/smt/smt_harvey_2.jpg

http://aro.as.arizona.edu/images/12_meter/IMG_4693_crop_ps.jpg


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“It’s the ciiiiiirrrcle of liiiiiife!”


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ALMA Prototype Antenna!!!


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Molecular Studies of PNe

The New Arizona Radio Observatory 12-meter!


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Planetary Nebulae Studied• Multiple transitions of CO, CS, and HCO+ in

K4-47, NGC 6537, M2-48, NGC 6720 (The Ring), and NGC 6853 (The Dumbbell)

• More in depth studies of NGC 6537 (The Red Spider) and M2-48

• Map of HCO+ J = 10 across NGC 6853• Maps of CO J = 43 and J = 32 in NGC

6537


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Spectra!

ISMS 2010, WG04ISMS 2011, TF11ISMS 2012, WH09


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Observatory Radio Edwards, Cox, & Ziurys 2014, ApJ, in print

HCN,CN,HNC

CS

HCO+

CORedman et al. 2003


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More in depth investigations…

• Finally starting to delve further into the chemistry of PNe beyond archetypical molecules like CO, CN, HCN, HCO+

• Beginning to see a more complex chemical inventory• When comparing these inventories, we found something

interesting: Carbon-rich, Oxygen-rich, and intermediate PNe, based off of their molecular inventory


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A Carbon-rich Planetary Nebula

• One of the best studied PNe is carbon-rich NGC 7027 (700 years)

• ARO telescopes

• CO, CN, CCH, C3H2, HCN, HCO+, HC3N, N2H+ (Zhang et al. 2008)

• LACK of CS and HNC

• NGC 6537 (The Red Spider) High excitation, C/O ~0.95

(1,600 years old)


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An Intermediate Planetary Nebula

Edwards & Ziurys 2013, ApJ, 770, L5


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• CO, CN, HCN, HNC, CCH, CS, SO, H2CO, HCO+, N2H+ and numerous 13C isotopologues

An Intermediate Planetary Nebula

Edwards & Ziurys 2013, ApJ, 770, L5

• NGC 6537 (The Red Spider) High excitation, C/O ~0.95

(1,600 years old)

• M2-48, Middle-aged at ~4,800 years, C/O ?


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An Oxygen-rich Planetary Nebula?

Edwards & Ziurys, in preparation

ISMS 2013, FA04


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• M2-48, Middle-aged at ~4,800 years, C/O ?

• CO, CN, HCN, HNC, CS, SO, SO2, SiO, HCO+, N2H+

and numerous 13C isotopologues

An Oxygen-rich Planetary Nebula?ISMS 2013, FA04

Edwards & Ziurys, in preparation


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Abundances

• Models don’t predict this amount of chemical content

• Now we are beginning to have enough information to see some chemical trends

• Seeing fossil molecules from the AGB phase

Molecular Abundances in Planetary Nebulae

Molecule M2-48 Red Spider NGC 7027

CO 1.0 x 10-4 1.1 × 10-4 1.1 × 10-4

13CO 8.3 × 10-5 7.4 × 10-6

C18O 1.5 × 10-6 3.8 × 10-7

CN 3.8 x 10-7 1.8 × 10-7 7.0 × 10-8

13CN 1.9 x 10-7 9.3 × 10-8 …

HCN 1.2 x 10-7 6.2 × 10-8 4.5 × 10-8

H13CN 4.0 x 10-8 2.6 × 10-8 3.9 × 10-9

HNC 4.7 x 10-8 3.1 × 10-8 < 4.1 × 10-11

HN13C 1.8 x 10-8 9.0 × 10-9 …

CCH - 6.9 × 10-8 5.4 × 10-8

CS 2.7 x 10-8 1.1 × 10-7 < 5.5 × 10-11

SO 2.0 x 10-7 2.1 × 10-8 …

H2CO - 2.2 × 10-8 < 1.3 × 10-10

HCO+ 1.1 x 10-7 2.6 × 10-8 4.8 × 10-8

SiO 2.4 x 10-8

SO2 1.2 x 10-7

N2H+ 9.8 x 10-8 7.8 × 10-9 3.8 × 10-9

c-C3H2 - < 1.1 × 10-7 8.3 × 10-9


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Insight into the Progenitor Star?

Molecules Seen in NGC 7027

Molecules Seen in NGC 6537

Molecules Seen in M2-48

CO, CN, HCN, HCO+, N2H+, CCH, C3H2, HC3N

CO, CN, HCN, HNC, HCO+, N2H+, CS, H2CO, CCH, SO

CO, CN, HCN, HNC, CS, HCO+, N2H+, SO, SO2, SiO

• Initial PPN chemistry, then freezout?

C>O C≈O C<O


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• Use molecular abundances to determine isotope ratios

M2-48• CNO equilibrium

abundance value (~3.4) of 12C/13C are along with high nitrogen content are indicative of hot-bottom burning


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• Use molecular abundances to determine isotope ratios

• CNO equilibrium abundance value (~3.4) of 12C/13C are along with high nitrogen content are indicative of hot-bottom burning

NGC 6537


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• NGC 6537 12C/13C from HCN and HNC are 3.5 and 2.4, respectively

• M2-48 12C/13C from HCN, HNC, and HCO+ are 3.0, 2.6 and 4.5, respectively

• Observational evidence of HBB• HBB occurs in stars with >4 Mʘ so the combination of these

things may also help ascertain progenitor star mass!

• (CNO equilibrium abundance value ~3.4)


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Conclusions• Planetary Nebulae

are rich in molecular content

• Use molecular observations to help classify the progenitor star

• Carbon/Oxygen ratio• Nucleosynthetic

pathways (HBB)• Stellar Mass


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Acknowledgements

• Dr. Ziurys• The rest of the

Ziurys Group• ARO Engineers,

Operators, Staff• NASA and NSF for

funding

http://chem.arizona.edu/ziurys/group.html


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Table 2. Molecular Abundances in M2-48

Molecule TKin (K) n(H2) (cm-3) N(cm-2) a f(X) a,b

CO c 45 1.3 × 105 4.5 × 1015 1.0 × 10-4 CN 55 d 2.9 × 105 e 1.7 × 1013 3.8 × 10-7

13CN 55 d 2.9 × 105 e 8.7 × 1012 1.9 × 10-7 HCN 55 d 5.6 × 105 5.2 × 1012 1.2 × 10-7

H13CN 55 d 5.5 × 105 1.8 × 1012 4.0 × 10-8 HNC 55 d 3.3 × 105 2.1 × 1012 4.7 × 10-8

HN13C 55 d 4.4 × 105 8.0 × 1011 1.8 × 10-8 SiO 55 9.0 × 105 1.3 × 1012 2.9 × 10-8 SO 55 d 3.1 × 105 1.1 × 1013 2.4 × 10-7

SO2 55 d 9.5 × 105 5.6 × 1012 1.2 × 10-7

CS c 55 2.9 × 105 1.2 × 1012 2.7 × 10-8 HCO+ c 55 d 1.3 × 105 5.0 × 1012 1.1 × 10-7 H13CO+ 55 d 1.3 × 105 f 1.1 × 1012 2.4 × 10-8

N2H+ 55 d 5.6 × 105 g 4.4 × 1012 9.8 × 10-8

CCH 55 d 2.9 × 105 e < 3.2 × 1012 < 7.1 × 10-8 SiS 55 d 2.9 × 105 e < 3.8 × 1012 h < 8.4 × 10-8

H2CO 55 d 2.9 × 105 e < 7.7 × 1012 h,i < 1.7 × 10-7 a Assuming a source size of ~20''×30''; see text b Assuming CO/H2 ~ 10-4; see text c From Edwards, Cox, & Ziurys (2014) d Fixed to value from CS and SiO fit e Fixed to value from CS fit f Fixed to value from HCO+ fit g Fixed to value from HCN fit h Assuming ΔV1/2 ~33 km/s i Assuming an ortho to para ratio of ~3


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Table 4: Measured Abundances in Observed Planetary Nebulae

Source Component Molecule

Rotational Diagram Radiative Transfer Modelingf(X) b

Trot (K) N(cm-2) Tkin (K) n(H2) (cm-3) Ntot(cm-2)

K4-47 Central CO 10 3.4 x 1016 10 2.0 x 105 5.1 x 1016 1.8 x 10-4

CS 11 5.1 x 1012 39 4.5 x 105 5.4 x 1012 1.9 x 10-8

HCO+ 39a 1.8 x 106 4.4 x 1012 1.5 x 10-8

NGC 6537 CO 49 9.4 x 1015 62 2.0 x 105 1.0 x 1016 4.3 x 10-5

CS 9 1.0 x 1013 76 1.0 x 105 9.9 x 1012 4.3 x 10-8

HCO+ 76a 1.5 x 105 2.2 x 1012 9.6 x 10-9

M2-48 CO 45 1.3 x 105 4.5 x 1015 1.0 x 10-4

CS 10 1.0 x 1012 55 1.4 x 105 1.2 x 1012 2.7 x 10-8

HCO+ 55a 6.2 x 104 5.0 x 1012 1.1 x 10-7

NGC 6720 Red CO 37 1.0 x 1015 38 2.0 x 105 1.0 x 1015 3.7 x 10-5

CS 15 2.5 x 1011 45 9.0 x 105 2.5 x 1011 9.3 x 10-9

HCO+ 45a 1.8 x 105 1.5 x 1011 5.6 x 10-9

Blue CO 29 6.7 x 1014 37 3.0 x 105 7.5 x 1014 2.8 x 10-5

CS 13 2.6 x 1011 44 5.9 x 105 2.6 x 1011 9.6 x 10-9

HCO+ 44a 8.6 x 104 2.3 x 1011 8.5 x 10-9

NGC 6853 Red CO 23 4.7 x 1014 27 2.1 x 105 4.3 x 1014 1.5 x 10-5

CS 12 2.2 x 1011 36 7.0 x 105 2.2 x 1011 7.6 x 10-9

HCO+ 36a 4.3 x 105 5.2 x 1010 1.8 x 10-9

Blue CO 22 1.2 x 1015 22 3.2 x 105 1.3 x 1015 4.5 x 10-5

CS 11 1.4 x 1011 32 6.0 x 105 1.4 x 1011 4.8 x 10-9

HCO+ 32a 2.2 x 105 2.2 x 1011 7.6 x 10-9

a Fixed to value from CS fit.b Relative to H2.

the 69 th international symposium on molecular spectroscopy june 19, 2014 comparative chemistry of...

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