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ATCA millimetre observations of young dusty disks

ATCA millimetre observations of young dusty disks. Chris Wright, ARC ARF, UNSW@ADFA Dave Lommen, Leiden University Tyler Bourke, Michael Burton, Annie Hughes, Jes Jorgensen, Sarah Maddison, Ewine van Dishoeck, David Wilner, Tony Wong. Aims.

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ATCA millimetre observations of young dusty disks

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  1. ATCA millimetre observations of young dusty disks Chris Wright, ARC ARF, UNSW@ADFA Dave Lommen, Leiden University Tyler Bourke, Michael Burton, Annie Hughes, Jes Jorgensen, Sarah Maddison, Ewine van Dishoeck, David Wilner, Tony Wong

  2. Aims • Through 3 and 12 mm continuum observations to investigate disk evolution and grain growth around a sample of young stars (T Tauri, Herbig AeBe) in southern molecular clouds • Through molecular emission to investigate the chemistry and dynamics of such disks

  3. Results 1 • TW Hya and HD100546 observed in 2001 and 2002 at 3 mm, published 2003 (Wilner et al., ApJ, 596, 597) • TW Hya detected in both continuum and HCO+ • Closest known T Tauri star • Spatially resolved in HCO+ 1→0 line • Narrow line width implies almost face-on disk • Substantial gas depletion • Herbig Be HD100546 detected in continuum only • Comet-like dust detected by ISO • Compact 3 mm source provides direct evidence of disk • Likely even more extreme gas depletion, consistent with highly processed nature of the dust, inference of planet(s)

  4. Results 1a – TW Hya HCO+, HD100546 continuum

  5. Results 2 • Survey conducted of T Tauri stars in Lupus (4) and Chamaeleon (10) 2003-2005 • Merging of two programs C996 and C1173 • 9 of 14 sources detected • Disk masses calculated • Millimetre slopes and dust opacity indices derived • Grain growth, up to mm sizes, is inferred • Presented at Protostars and Planets 2005 (Lommen et al.)

  6. Results 2a – 4 Lupus, 5 Cham

  7. Results 2b – Fluxes, α, β, mass

  8. Results 3 • During bad 3 mm weather attempted 12 mm observation of HD100546 and HD135344 • A clear detection of HD100546 • 1.65 mJy with rms of 0.12 mJy/beam • Consistent with falling SED from 31 mJy at 3 mm • But what is emission mechanism? • Large dust grains, e.g. cm sized pebbles? • Or free-free? • HD135344 not detected at 0.3 mJy level (rms) • Difference in molecular emission toward the two sources, CO seen toward HD135344, not for HD100546 • Difference in dust species toward the two sources, crystalline silicates in HD100546, PAHs in HD135344

  9. Results 3a – HD100546 at 18.5 GHz

  10. Results 3b – HD135344 at 23.5 GHz

  11. Future observations 1 – HD100546 • 12 mm monitoring of HD100546 to look for time variation • If stable, then stronger case for “pebbles” • If not, then likely stellar magnetic activity • 3 and 6 cm observations of HD100546 to determine spectral index • So potentially determine emission mechanism, e.g. free-free from a wind or otherwise • Attempt to resolve HD100546 at 3 and/or 12 mm • 12 mm observations of the best disk survey targets

  12. Future observations 2 - Survey • Determine flux at 3 points between 85 and 105 GHz to potentially better constrain the spectral index and so dust particle sizes • Consistent set of instrument and flux calibrators • Observe more chemical species to better determine disk chemistry and/or dynamics • Abundances, rotation, correlation with continuum (gas depletion with grain growth?) • Extend sample to include more targets observed by Spitzer • Independent measures of grain sizes • Spatially resolve best targets • Better constrain disk physics (surface density, irradiated accretion models)

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