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Molecular Surveys of the Disks Encircling T Tauri/Herbig Ae Stars

Molecular Surveys of the Disks Encircling T Tauri/Herbig Ae Stars. Geoffrey A. Blake CalTech. Chemistry as a Diagnostic of Star Formation Waterloo, Canada 23Aug2002. People Really Doing the Work!. Caltech: -Jacqueline Kessler, Chunhua Qi (now at the SMA/CfA) -Adwin Boogert

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Molecular Surveys of the Disks Encircling T Tauri/Herbig Ae Stars

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  1. Molecular Surveys of the Disks Encircling T Tauri/Herbig Ae Stars Geoffrey A. Blake CalTech Chemistry as a Diagnostic of Star Formation Waterloo, Canada 23Aug2002

  2. People Really Doing the Work! Caltech: -Jacqueline Kessler, Chunhua Qi (now at the SMA/CfA) -Adwin Boogert Leiden w/Ewine van Dishoeck: -Klaus Pontoppidan, Gerd Jan van Zadelhoff, Wing-Fai Thi (now at UCL) Arizona: -Michiel Hogerheijde SFCHEM 2002 23Aug02

  3. Study Isolated Disks (Weak/No Outflow) Beckwith & Sargent 1996 SFCHEM 2002 23Aug02

  4. Spectroscopy of “Disk Atmospheres” G.J. van Zadelhoff 2002 IR disk surface within several tens of AU (sub)mm disk surface at large radii, disk interior SFCHEM 2002 23Aug02

  5. MM-Wave CO Traces Dynamics, Others? M. Simon et al. 2001, PdBI Measure: R_disk M_star Inclination w/resolved images. Dutrey et al. 1997, IRAM 30m Kastner et al. 1997, TW Hya, JCMT SFCHEM 2002 23Aug02

  6. Star Sp Type d(pc) Teff(K) R(Rsun) L(Lsun) M(Msun) Age(Myr) LkCa 15 K5:V 140 4365 1.64 0.72 0.81 11.7 GM Aur K5V:e 140 4060 1.78 0.8 0.84 1.8 HD 163296 A0 120 9550 2.2 30.2 2.3 6.0 MWC 480 A3 130 8710 2.1 32.4 2.0 4.6 LkCa 15 OVRO+CSO/JCMT MM-Wave Disk Survey The Sample (drawn from larger single dish survey) MWC 480 Mannings, Koerner & Sargent 1997 Koerner & Sargent 1995 SFCHEM 2002 23Aug02 See also poster #67 (SMA maps)

  7. OVRO+CSO/JCMT MM-Wave Disk Survey II van Zadelhoff et al. 2001 Combine 3/1.3 mm array images w/higher J spectra to constrain OUTER disk properties, chemical networks. SFCHEM 2002 23Aug02

  8. Disk Ionization Structure: CO and Ions Disk properties vary widely with radius, height; and depend on accretion rate, etc. (Aikawa et al. 2002, w/ D’Alessio et al. disk models, poster #21). Currently sensitive only to R>100 AU in gas tracers, R<100 AU dust. CO clearly optically thick, other species likely to be as well. Model via 2D Monte Carlo using disk structure and chemical models as input, vary to fit observations (Kessler talk).

  9. Source L*(L ) CN/HCN Hdust/hgas LkCa 15 0.72 ~ 10 1.0 GM Aur 0.80 << 1 4.0 MWC 480 30.2 ~ 4 1.7 HD 163293 35.2 >> 50 - UV Fields: HCN and CN [CN]/[HCN] traces enhanced UV fields (Fuente et al. 1993, Chiang et al. 2001) LkCa 15 Molecular distribution ring-like? Photochemistry or desorption? SFCHEM 2002 23Aug02 Qi et al., in prep

  10. LkCa 15 CS 2-1 LkCa 15 C34S 5-4 Sulfur Species NT(CS) = 1013-1014 cm-2 Upper limits only for H2S,SO,SO2 CS dominant Reminiscent of “early time” chemistry. SFCHEM 2002 23Aug02

  11. Grain chemistry: CH3OH, SiO, H2CO CH3OH, H2CO - grain surface production SiO - grain sputtering + gas phase rxn Si + O2SiO + O h h Si H2CO H2CO CH3OH CH3OH SFCHEM 2002 23Aug02

  12. Are Even Larger Molecules Present? • Observations can test gas/grain models, HIFI and arrays can uniquely access small, dense cores & disks. • Laboratory spectra urgently needed, work underway (posters #11,84). Grain Chemistry Model (Charnley 2001) Glycine SFCHEM 2002 23Aug02

  13. Are these large disks unusual? CO, HCO+ (and NNH+) chemistry well predicted by disk models. Other species, esp. CS, CN, HCN, much more intense, with unusual emission patterns in some cases (LkCa 15). MM-continuum surveys do not reveal such large, massive disks in similarly aged clusters (IC348) and clouds (NGC 2024, MBM12). Environment? Need better (sub)mm-wave imaging capabilities. SFCHEM 2002 23Aug02

  14. Future of the U.S. University Arrays – CARMA CARMA = BIMA (9 6.1m) + OVRO (6 10.4m) + SZ Array (8 3.5m) telescopes. SUP submitted 2003 SZA on site 2004 move OVRO 2004 move BIMA 2005 full operations Juniper Flat

  15. How can we probe the planet-forming region? (pre-ALMA) The size scales are too small even for the largest current near-IR arrays… Spectroscopy to the rescue! Theory Jupiter (5 AU): V_doppler = 13 m/s V_orbit = 20 km/s Simulation G. Bryden Observation?

  16. High Resolution IR Spectroscopy & Disks R=10,000-100,000 (30-3 km/s) echelle spectrographs (ISAAC,MICHELLE, NIRSPEC, PHOENIX,TEXES) on 8-10m telescopes can now probe “typical” T Tauri/Herbig Ae stars: Keck CO M-band fundamental NIRSPEC R=25000 VLT

  17. Orientation is Pivotal in the IR! Edge-on absorption. L1489: Gas/Ice~10/1, accretion. CRBR2422.8: Gas/Ice~1/1, velocity field? Elias 18 Gas/Ice<1/10 (Shuping et al.) Poster #79 SFCHEM 2002 23Aug02 H3+ in absorption?

  18. Edge-on Disks & Comets? N7538 W33A Hale-Bopp Water 100 100 100 CO 10 1 23 CO2 16 3 6 CH4 1 0.7 0.6 H2CO 3 2 1 CH3OH 9 10 2 HCOOH 2 0.5 0.1 NH3 10 4 0.7 OCS 0.1 0.05 0.4 IR studies of edge on disks could map out both gas phase & grain mantle composition, compare to that found in massive YSOs, comets. SFCHEM 2002 23Aug02

  19. More typically, emission is seen in M-band GSS30 – Class I T Tauri star, accretion shock emission? (NIRSPEC, R~25000) Pontoppidan et al. 2002 (ISAAC, R~5000, poster #66) Broad H I from accretion/outflow, narrow CO from disk. Gap tracer (Carr et al. 2001, DQ Tau)? SFCHEM 2002 23Aug02

  20. How is the CO excited in these disks? CO and 13CO rotation diagrams show two components, but even the “hot” component is <500 K. Very small amounts of gas. Collisional excitation unimportant at these temperatures, Resonant scattering! Need detailed radiative transfer models (similar effects seen in massive YSOs, Mitchell et al., van der Tak et al.). SFCHEM 2002 23Aug02

  21. Where does the CO emission come from? Flared disk models often possess 2-5 micron deficiency in model SEDs, where a “bump” is often observed for Herbig Ae stars. Dullemond et al. 2002 Explanation: Dust sublimation near the star exposes the inner disk to direct stellar radiation, heating the dust and “puffing up” the disk. SFCHEM 2002 23Aug02

  22. SED Fits versus IR Interferometry Fits to AB Aur SED yield an inner radius of ~0.5 AU (and 0.06 AU for T Tau). (Monnier & Millan-Gabet 2002, astro-ph/0207292) Dullemond et al. 2002 This model can now be directly tested via YSO size determinations with K-band interferometry. Intense dust emission pumps CO, rim “shadowing” can produce moderate T_rot.

  23. Future “Near”-IR (1-5 um) Spectroscopy Brittain & Rettig 2002, poster #10 Many other species and disk types (transitional, debris, etc.) should be examined in both absorption (edge on disks) and emission: SFCHEM 2002 23Aug02 H3+, CH4, H2O, OCS...

  24. Mid-IR Spectroscopy – Unique access to “warm” H2 Rotational H2 lines potentially provide direct measure of gas mass w/o need for abundance calibrations. Thi et al. 2001 Additional studies/confirmation in optically thick, “transitional” pivotal. Difficult, but doable, from the ground. SFCHEM 2002 23Aug02

  25. SIRTF - IRAC (mid-IR cameras, 3.6 4.5, 5.8, 8.0 mm) - MIPS (far-IR cameras, 24, 70 160 mm, R=20 SED mode) - IRS (5-40 mm long slit,R=150, 10-38 mm echelle, R=600) 09 Jan 2003 launch • - GTO observations • - Legacy program • - General observations SFCHEM 2002 23Aug02

  26. SIRTF – Spectroscopy of Dust and Ice ISO SWS data on A stars, SIRTF can do sun-like stars, high spectral resolution needed for gas phase features. Evans et al., c2d ~170 sources first look + follow up of mapping (poster #46). Meyer et al. Photometry~350 sources, IRS follow up (Class III). SFCHEM 2002 23Aug02

  27. Disk Spectroscopy - Conclusions (Sub)mm-wave instruments can only study the outer reaches of large disks at present. Expanded arrays (CARMA, eSMA, ALMA) will provide access to much smaller scales. HIFI will enable first assault on water in the cold regions of disks, and may provide a new window on molecular complexity. High resolution IR spectroscopy just starting, is immensely powerful, and will provide unique access to the 1-10 AU region until the advent of ALMA, large IR interferometers. SIRTF will provide many new targets! SFCHEM 2002 23Aug02

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