65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 Exotic Metal Molecules In Oxygen-Rich Envelopes: Detection of AlOH(X 1 Σ + ) In VY Canis Majoris E. D. Tenenbaum and L. M. Ziurys Dept. of Chemistry, Dept. of Astronomy Arizona Radio Observatory Steward Observatory University of Arizona

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 AlOH: A Short History AlOH: one original molecules studied in Ziurys lab - Rotational spectrum measured by mm direct absorption methods - Measured by Apponi, Barclay, & Ziurys (1993) at ASU Previous electronic spectroscopy by Duncan group Calculations by Shaefer et al. Conducted astronomical searches at NRAO 12 m Sources: Orion, SgrB2, IRC+10216, W Hydra Original spectrometer ASU 1992

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 ARO Survey of VY CMa and IRC mm survey (210 – 285 GHz) of VY Canis Majoris (VY CMa) and IRC (Thesis of Emmy Tenenbaum) Conducted with ARO SMT: rms noise level ~ 3 mK IRC+10216: famous carbon-rich circumstellar shell VY CMa is oxygen-rich supergiant - massive circumstellar envelope Explore chemical content O-rich shells Ignored over last few decades Compare with C-rich chemistry Test new Band 6 ALMA mixers SMT VY CMa

65th International Symposium on Molecular Spectroscopy June 21 – 25, GHz 284 GHz VY CMa In survey, came across an interesting line…. Frequency of J = 9 → 8 transition of AlOH Found line at J = 7 → 6 frequency Line at J = 5 → 4 frequency (at ARO 12 M) frequencies J = 8 → 7 obscured by SO

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 Line Parameters for AlOH in VY CMa TransitionFrequency (MHz) ηBηB Θ b (")T R (K)V LSR (km s -1 ) ∆V 1/2 (km s -1 ) J = 9 → 8 283, ± ± ± 2.1 J = 8 → 7251, J = 7 → 6 220, ± ± ± 2.7 J = 5 → 4157, ± ± ± 8 Narrow line profiles for VYCMa  V 1/2 typically ~ 40 – 60 km/s AlOH coming from dust acceleration zone  gas has not reached terminal velocity Log r (cm) R*R* R1R1 Star Dust Shell Acceleration Zone V exp ~ 15 km s -1 T ~ 1000 K cm -3 T ~ 25 K 10 5 cm -3 UV

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 Radiative Transfer Analysis of Lines Code of Bieging and Tafalla (1993) Distance of 1.14 kpc to VY CMa(Choi et al. 2008) Spherical flow: mass loss rate of 2.6 × M  yr -1 Collisional rates HCN-H 2 system (none exist for AlOH) V exp ~ 10 km/s: stellar radius ~ 0.13'' (11 R * ) or 2.2 × cm Based on H 2 O masers (Richards et al. 1998) r outer ~ 11 R * and r inner ~ 2 R * Best fit to line profiles: f (AlOH/H 2 ) ~ 1 × Source size of ~0.26'' T gas =  = (Zubko et al 2004) AlOH contains ~ 1% of Al abundance AlOH/AlO ratio ~ 17/1 AlOH dominant carrier of aluminum

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 LTE Modeling Results AlOH is in dust acceleration zone At r ~ 11 R *, : T ~ 600 K and n(H 2 ) ~ 10 8 cm -3 AlOH formed by LTE chemistry Model calculations (Tsuji 1973): ABUNDANCE vs. STELL RADIUS AlOH abundance f ~10 -6 from 2 to 10 R * (T K ~ 700 – 1500 K)  Most abundant Al Species AlO abundance peaks near photosphere at ~ and then drops Abundances of other molecules..

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 Abundances of Al, Na, and K-bearing Molecules in VY CMa SpeciesObserved Abundance a) LTE-predicted Abundance AlOH1 × × NaOH≤ 3 × × KOH≤ 1 × × AlCl≤ 5 × × NaCl4 × × KCl≤ 4 × × AlO6 × × Data from survey Model overestimates AlOH, underestimates AlO Predicts AlCl abundance (upper limit) In general, model overestimates observed abundances

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 Where are other Metal-Bearing Molecules ? Model predicts KOH, NaOH, KCl in O-rich shells Condensation into grains Shock waves from star Also may be a question of nucleosynthesis Only see Al and Na in molecules in VY CMa Supergiant star likely undergoing H-Shell burning Proton addition to 26 Mg and 22 Ne leads to 27 Al and 23 Na Enrichments of Na and Al observed in M and A-type supergiants (Gonzales and Wallerstein 2000) Clearly need to observe other O-rich envelopes in detail  understand chemical trends Other metal hydroxides might be observable in O-rich shells

65th International Symposium on Molecular Spectroscopy June 21 – 25, 2010 NSF Astronomy NASA Astrobiology