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

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

Results 1 TW Hya and HD 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+ 10 line Narrow line width implies almost face-on disk Substantial gas depletion –Herbig Be HD 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)

Results 1a – TW Hya HCO+, HD continuum

Results 2 Survey conducted of T Tauri stars in Lupus (4) and Chamaeleon (10) –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.)

Results 2a – 4 Lupus, 5 Cham

Results 2b – Fluxes, α, β, mass

Results 3 During bad 3 mm weather attempted 12 mm observation of HD and HD –A clear detection of HD 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? –HD not detected at 0.3 mJy level (rms) Difference in molecular emission toward the two sources, CO seen toward HD135344, not for HD Difference in dust species toward the two sources, crystalline silicates in HD100546, PAHs in HD135344

Results 3a – HD at 18.5 GHz

Results 3b – HD at 23.5 GHz

Future observations 1 – HD mm monitoring of HD 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 HD to determine spectral index –So potentially determine emission mechanism, e.g. free- free from a wind or otherwise Attempt to resolve HD at 3 and/or 12 mm 12 mm observations of the best disk survey targets

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)