64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of...

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64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope of VY Canis Majoris E.D. Tenenbaum and L.M. Ziurys Department of Chemistry Department of Astronomy Arizona Radio Observatory, Steward Observatory University of Arizona A rizona O bservatory R adio A rizona O bservatory R adio

Transcript of 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of...

Page 1: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

Millimeter Detection of AlO (X2Σ+): Metal Oxide Chemistry in the Envelope

of VY Canis Majoris

E.D. Tenenbaum and L.M. ZiurysDepartment of ChemistryDepartment of Astronomy

Arizona Radio Observatory, Steward ObservatoryUniversity of Arizona

Arizona

ObservatoryRadio

Arizona

ObservatoryRadio

Page 2: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

Small Number Statistics and Interstellar Chemistry• Over 140 interstellar molecules (and similar number of chemical models)• Only a handful of astronomical sources carefully studied

Are we “missing” sources with different chemistry ???

• Circumstellar Material: C-Rich shells principally observed (IRC+10216)• Oxygen-rich shells neglected• A closer look at O-rich envelopes

Circumstellar gas of O-rich Supergiant Star

VY Canis Majoris (VY CMa)• Spectral Line survey in 1 mm band (210 – 285 GHz)• First comprehensive study of

O-rich circumstellar environment• Observed IRC+10216 for comparison

10 "

Envelope of VY CMa

Page 3: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

Prime Time at the ARO Submillimeter Telescope

Arizona

ObservatoryRadio

Arizona

ObservatoryRadio

• Arizona Radio Observatory (ARO) operates:

- Submillimeter Telescope (SMT)

-12 m at Kitt Peak• Installed new 1 mm receiver at SMT• Utilizes ALMA Band 6 mixers• Achieve noise levels of 3 mK ( 1 sigma)

12 m SMT

1 mm insert

Page 4: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

• Collected data in 1 GHz sections• 3 year project using over 2000 hours in telescope time

ARO 1 mmSurvey ofVY CMa andIRC+10216

PhD ThesisE.Tenenbaum

Page 5: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

RAW Data: SMT at 1 mm

• No baseline

subtraction• No smoothing• No other

manipulations• 30 hours

integration

AlO: N = 7→ 6

H2O maser

7 years ofwork atthe SMT….but look at theSpectra !

Page 6: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

Observations of AlO (X2Σ+)• Two 1 mm transitions: N = 7 → 6 and

N = 6 → 5 at 267.9 and 229.6 GHz• Observed with SMT• One 2 mm line measured with the 12 m

at 153 GHz (N = 4 → 3)• Different line profiles

Al hyperfine structure: varies with

frequency

Free radical

Lab spectrumfromYamada et al.(1990)

Page 7: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

..............

5"

Arc I

Arc II

CNT

(Ziurys et al. 2007 Nature)

VY CMa: Complex Source

• Spherical wind

- inner flow with

narrow linewidths

- outer flow with

full expansion

velocity • Blue/Red-shifted

outflows

blue red

Page 8: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

Line Parameters of Observed AlO Transitions

Transition ν (MHz) Θb VLSR (km/s) TA* (mK)

N = 76 267937 28 25 ± 5 7 ± 2

N = 65 229670 33 25 ± 6 3 ± 1

N = 43 153124 41 27 ± 6 1.4 ± 0.5

AlO

Ntot ~ 2 × 1015 cm-2

Trot ~ 230 K

f (AlO/H2) ~ 10-8

• Linewidths of ~ 10 - 15 km/s

Accounts for HF components in profiles

• Identical to NaCl: θs ~ 0.5“

• Inner part of spherical flow at r ~ 30 R*

Page 9: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

12 13 14 15 16 17 18 19Log r (cm)

R*

R1

Star

Dust Shell Acceleration Zone

Vexp ~ 15 km s-1T ~ 1000 K1010 cm-3

T ~ 25 K105 cm-3

UV

UV

UV

• Molecules created at LTE near stellar photosphere (T ~ 1000 -2000 K)

• For AlO (r ~ 30 R*): near photosphere

Implications for Circumstellar Chemistry

ObservedAbundanceof AlO

But AlOHAnd Al2OMoreAbundant !

Page 10: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

And Even More Aluminum… • AlOH also identified in VY CMa• Emission weaker than AlO

More than LTE chemistry• Shocks disrupt condensation process

into Al2O3

Lab spectrum from 1993 (Apponi, Barclay and Ziurys)

Page 11: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

• 20 molecules in VY CMa (OH, NH3)

• Spectrum dominated by SO2, SiO, SiS

• What else ??

• New molecules in O-rich circumstellar gas: AlO, PO, AlOH• First time metal oxides and hydroxides seen in interstellar molecules• Oxygen-rich Circumstellar environment fosters different chemistry• Relate to grains, shocks, and photospheric molecules• Electronic Bands of AlO observed in stellar atmospheres

Conclusions and Future Directions

AlO: A → X

V4332 Sgr

CO CN CS HCN HCO+ HNC

SO2 SiS SiO NS H2S H2O

SO PN PO NaCl AlO AlOH

Page 12: 64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009 Millimeter Detection of AlO (X 2 Σ + ): Metal Oxide Chemistry in the Envelope.

64th International Symposium on Molecular Spectroscopy June 22 – 26, 2009

NSF Astronomy

NASA Astrobiology

Arizona

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Arizona

ObservatoryRadio