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The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Comparative Chemistry of Planetary Nebulae:
Arizona
Observatory Radio
Jessica L. EdwardsLucy M. ZiurysThe University of ArizonaDepartments of Chemistry and Astronomy
The Role of the Carbon to Oxygen Ratio
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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)
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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!
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
“It’s the ciiiiiirrrcle of liiiiiife!”
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
ALMA Prototype Antenna!!!
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
Molecular Studies of PNe
The New Arizona Radio Observatory 12-meter!
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
Spectra!
ISMS 2010, WG04ISMS 2011, TF11ISMS 2012, WH09
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio Edwards, Cox, & Ziurys 2014, ApJ, in print
HCN,CN,HNC
CS
HCO+
CORedman et al. 2003
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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)
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
An Intermediate Planetary Nebula
Edwards & Ziurys 2013, ApJ, 770, L5
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
• 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 ?
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
An Oxygen-rich Planetary Nebula?
Edwards & Ziurys, in preparation
ISMS 2013, FA04
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
• 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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
Insight into the Progenitor Star?
• 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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
Insight into the Progenitor Star?
• 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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
Insight into the Progenitor Star?
• 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)
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
Acknowledgements
• Dr. Ziurys• The rest of the
Ziurys Group• ARO Engineers,
Operators, Staff• NASA and NSF for
funding
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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
The 69th International Symposium on Molecular Spectroscopy June 19, 2014
Arizona
Observatory Radio
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.