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Gas Chemistry in Primordial Disks: High-Sensitivity Probing with CRIRES/NIRSPEC

Investigating gas chemistry in primordial disks using CRIRES/NIRSPEC instruments to detect molecular tracers in low and high-mass stars. The study aims to uncover abundance and temperature variations with spectral types.

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Gas Chemistry in Primordial Disks: High-Sensitivity Probing with CRIRES/NIRSPEC

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  1. CRIRES / NIRSPEC – Gas Chemistry in Primordial Disks With High Sensitivitiy Avi M. Mandell NASA Goddard Collaborators: Michael J. Mumma (NASA-GSFC) Geoffrey Blake (CalTech) Klaus Pontopiddan (CalTech) Jeanette Bast (Leiden) Ewine van Dishoeck (Leiden/Garching) Colette Salyk (Univ. of Texas)

  2. Probing the L-band: 3 – 4 μm • Low-mass stars: • Extremely rich in molecular tracers in the C-,O-, and N-bearing chemical trees (below) • High-mass stars: Only OH? Why? How do abundances/temperatures change with spectral type? Expected line flux, based on abundances from disk models, for species detectable in two CRIRES settings; dotted line is for S/N = 500

  3. Reduction Steps: Reaching the Photon Limit A. Fit Atmospheric Models for for Science & Calibration Stars - Airmass, Molec. Abund., & Temp B. Subtract Calibr. Star residuals from Science Star residuals to remove remaining systematics C. Use Fourier filter for remove remaining uncorrected fringing

  4. Comparing New Reductions with Old Calibration Star-Only Analysis

  5. First CRIRES Results • S/N ~ 500 • Excellent H2O, OH, possibly higher vibrational OH and NH3 First tentative detection Of CH4?

  6. First CRIRES Results • Ammonia / HCN Region: Incredibly rich with detected molecules – working to develop modeling tools for multiple molecules/parameters • [OH/H2O] ~ -0.5, [HCN/H2O] ~ -1.0, [C2H2/H2O] ~ -1.5, • [NH3/H2O] =???

  7. First CRIRES Results • Ammonia / HCN Region: Incredibly rich with detected molecules – working to develop modeling tools for multiple molecules/parameters • [OH/H2O] ~ -0.5, [HCN/H2O] ~ -1.0, [C2H2/H2O] ~ -1.5, • [NH3/H2O] =???

  8. Proposals / New Data: Just proposed for 8 new stars w/ varying spectral type, very deep, over two settings. More sources / more lines may be available in the CRIRES / NIRSPEC archives, upcoming NIRSPEC runs HCN: Strong detection in one star (AS 205), possible additional sources (DR Tau?) have been identified by Klaus & Colette CH4: Only one star (DR Tau) w/ very tentative detection – wait for more data? NH3, C2H2: Unclear – must analyze with multi-molecule fitting code, look at NIRSPEC data Modeling: LTE relatively easy, but more sophisticated models are needed (Klaus/Rowin) Publishing: Single-source with several molecules (AS205)? Or multiple sources (AS205, DR Tau), but with patchier data? Wait for non-LTE modeling? Current Status and Plans

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