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Millimetre observation of pre planetary disks
Pictoris Fomalhaut Vega Holland et al. (1998) Nature JCMT 0.85 mm

Chris Wright, Honorary Visiting Fellow, UNSW@ADFA Prof. Ewine van Dishoeck, Leiden & Dr. Tyler Bourke , CfA


MM observations of pre-planetary disks
· Aims ­ to study the evolution of the gas and dust through the phases of a young stars life, e.g. from deeply embedded Young Stellar Object to T Tauri and Herbig Ae/Be through to optically revealed main -sequence stars. This will provide information on dust and gas processing, and disk dispersal (planetary formation?) timescales. ­ to conduct such a study in the rich southern hemisphere skies, e.g. the Chamaeleon, Corona Australis , Lupus, Vela and Ophiuchus clouds, and compare their processing with that of our solar system


From Michiel Hogerheijde, adapted from Shu et al. (1987)


MM observations of pre-planetary disks
· Methods
­ Millimetre single dish (Mopra) and interferometric (ATCA) spectral line and continuum observations, to obtain gas chemistry, kinematics (infall, outflow, rotation), gas and cold dust spatial distribution ­ Mid - infrared spectroscopic observations of the 10, 20 micron silicate bands (Michelle on UKIRT/Gemini-N, TIMMI2 on ESO 3.6 m, T-ReCS on Gemini-S), to obtain warm dust mineralogy, size, spatial distribution


Embedded

Debris disk

T Tauri, Herbig Ae/Be


Images of disk "evolution"


The "evolution" of the 10 µm silicate band


Michelle - Prospects for High Resolution Spectropolarimetry


History 1
· 1984, Aumann et al. used IRAS to detect excess dust emission at 15, 60 and 100 µm toward the main sequence star Vega ( Lyrae) · A search of IRAS database conducted, and further detections like Pictoris reported, e.g. Aumann (1985), Sylvester et al. (1996) · Ground- based follow-up imaging and spectroscopy dust distributed in a so -called "debris" disk, in some cases with warps and gaps indicative of a planetary system


12 µm image of Pictoris

· Age about 20 Myr, cf. 4.5Gyr for the Sun · Disk extent more than 100 AU · Depletion and warp at < 40 AU at least one planet


AAT Observations of Pictoris and Comet Halley

Sitko et al. (1999) - "To understand better how Pic and other main sequence stars with debris disks evolved into their present state, we need to investigate their evolutionary precursors."


Comet Hale-Bopp AAT NIMPOL 11.5 µ m August 1996 3.6 AU


HD 100546 and Comet Hale-Bopp
· Comet = disk =crystalline/amorphous silicate mixture
­ short lifetime of dust needs replenishment ­ infalling /colliding comets

· Crystalline silicates not seen in ISM · Crystallised in disk before comet formation
­ How?


History 2
· But what about the gas? · Searches conducted for molecular emission
­ Embedded YSOs by Hogerheijde (1998), Padgett et al. (1999) ­ T Tauri stars by Sargent & Beckwith (1991), Zuckerman et al. (1995) ­ Herbig Ae/Be stars by Mannings & Sargent (1997) ­ Debris disks by Liseau & Artymowicz (1998), Coulson et al. (1998), Greaves et al. (2000)


But .......
· Whilst gas was detected and imaged toward the younger phases, no mm molecular emission was detected toward the debris disks - where is the gas?
­ Depleted by planet formation, dissociated, frozen out or beam diluted by single dish?

· Liseau & Artymowicz (1998):
­ "the testing of [these alternatives] has to await the advent of the new generation of millimeter interferometers in the southern hemisphere"


The gas content of planet building disks
HD 100546 HCO+ Mopra

· Little or no gas detected around socalled "debris" disks using ground -based instrumentation
­ e.g. HD100546, known for its "solar-system-like" dust properties ­ But where is the gas?


Molecular hydrogen in disks
· CO and other molecules not previously found in "debris" disks · Used up in planet formation, frozen out, dissociated, or beam dilution? · But these gases are only trace constituents - what about H2? · ISO observations
­ Jovian planet formation can occur on timescales up to 20 Myr Thi et al. (2001), Nature


Mopra observations of "relic" disks


Mopra observations of HH100 IR

A deeply embedded Young Stellar Object


Mopra observations of HD 100546
Augereau et al. (2001) HST 1.6 µ m


Mopra observations of HD 142527

· Thought to be an isolated Herbig AeBe star · CO 1-0 detected on a scale of tens of arcminutes , but probably not "bound" to the object, e.g. disk or outflow · But star is definitely associated with a molecular cloud


Mopra observations of TW Hya
Trilling et al. (2001) 1.65 µ m - face- on disk Wilner et al. (2000) 7mm


TW Hya JCMT Multi species and transition van Zadelhoff et al. (2001, A&A, 377 566)

Only "warm" gas, T~50 K, traced by higher J transitions is detected towards TW Hya Little cold gas present!


Mopra observations of HD 163296
Grady et al. HST STIS (2000 ApJ 544 895)

Mannings & Sargent OVRO CO 2- 1 (1997 ApJ 490 792)


HD 163296 JCMT CO 3-2 Thi et al. (2001, ApJ, 561 1074)

Higher J transitions, which trace warmer gas, are less affected by unrelated emission nearby or along the line -of-sight


Mopra conclusions
· CO 1-0 detected toward 3 objects ­ HD 100546, where it is extended and associated with the molecular cloud in which the object lies ­ HD 142527 ditto need for interferometer to reveal small-scale emission ­ HD 163296, where the signature of disk rotation can be discerned, but interpretation is aided by pre-existing interferometric observations · No other detections of CO 1-0, HCO+ 1-0 or CS 2-1 were made. This might indicate that cold gas (say 50 K) is not a significant component of many disks, e.g. TW Hya.


ATCA 3 mm observations
Henning et al. (1998) SEST 1.3 mm Wilner et al. (2000) VLA 7 mm

· 2 "interesting" objects selected (before Mopra data)
­ HD 100546 and TW Hya in HCO+ 1-0 transition

· Expected 3 mm continuum fluxes are 0.1 Jy for HD 100546 and 0.07 Jy for TW Hya


ATCA 3 mm recommendations
· · · · ATCA data not yet processed! A learning experience.... CO 1-0 115 GHz would have been preferred if available Observe at night! Conditions were much better! Use one correlator channel for continuum and other for spectral line (broad and narrow band) · Be sure of your source barycentric velocity as frequency has to be corrected in schedule file · Find a good strong phase calibrator (if possible) · To ATNF - continue to support Mopra as a training and "extended structure" instrument. Six weeks of community use per year is not enough!


Mopra observations of the AFGL 4176 outflow

· AFGL 4176 high velocity CO wings on either side of line core bipolar outflow


K3-50 Bipolar Outflow and Disk
· Via mid -IR polarisation data two magnetic field components were discovered
­ one from cold dust lies in the plane of the rotating gas (HCO+) toroid ­ the other from warmer dust is aligned with the radio jet and bipolar molecular outflow Howard et al. (1997 ApJ 477 738)


Mid -Infrared Spectra

· · ·

TW Hya Sitko et al. (2000)

HD 163296 HD 31648 Sitko et al. (1999)


IRAS LRS Spectra of "Vega-like" stars


Ground based spectra of " Vega-like" stars

Sylvester et al. (1996, MNRAS 279 915)